JP4961710B2 - Zoom lens and imaging apparatus - Google Patents

Description

  The present invention relates to a novel zoom lens and an imaging apparatus. Specifically, the present invention relates to a zoom lens suitable for an imaging device that receives light by an imaging element such as a video camera or a digital still camera, and an imaging device using the zoom lens.

  2. Description of the Related Art Conventionally, as a recording means in a camera, an object image formed on the surface of an image sensor is captured by an image sensor using a photoelectric conversion element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor). A method is known in which the light amount of a subject image is converted into an electrical output by a conversion element and recorded.

  With recent advances in microfabrication technology, the central processing unit (CPU) has been increased in speed and the storage medium has been highly integrated, so that large-capacity image data that could not be handled before can be processed at high speed. It has become. In addition, the light receiving element is also highly integrated and downsized. The high integration enables recording at a higher spatial frequency, and downsizing allows the entire camera to be downsized.

  However, due to the high integration and miniaturization described above, there is a problem that the light receiving area of each photoelectric conversion element is narrowed, and the influence of noise increases with a decrease in electrical output. In order to prevent this, the amount of light reaching the light receiving element is increased by increasing the aperture ratio of the optical system, and a minute lens element (so-called micro lens array) is arranged immediately before each element. It was. The microlens array restricts the exit pupil position of the lens system instead of guiding the light beam reaching between adjacent elements onto the element. When the exit pupil position of the lens system approaches the light receiving element, that is, when the angle formed by the chief ray reaching the light receiving element with the optical axis increases, the off-axis light beam toward the screen periphery forms a large angle with respect to the optical axis, As a result, the light does not reach the light receiving element, leading to insufficient light quantity.

  Conventionally, various zoom types have been proposed as zoom lenses for video cameras that receive light by an image sensor.

  For example, in Patent Document 1 and Patent Document 2, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, A so-called positive / negative positive / positive four-group zoom lens configured by four lens groups of a fourth lens group having positive refractive power is disclosed. These positive, negative, positive and positive four-group zoom lenses are arranged such that when the lens position changes from the wide-angle end state to the telephoto end state, the second lens unit moves to the image side to compensate for variations in the image plane position. The group moves, and the variation of the image plane position due to the variation of the subject position is compensated by the movement of the fourth lens group.

  In these positive, negative, positive and positive four-unit zoom lenses, since there is only one lens group having a negative refractive power, negative distortion is likely to occur in the wide-angle end state. For this reason, the third lens group is composed of a positive lens and a cemented lens of a positive lens and a negative lens, and the lens surface closest to the image side of the third lens group faces a strong concave surface toward the image side, thereby causing negative distortion aberration. Was corrected well.

  Accordingly, there has been proposed a zoom lens in which a fifth lens group that is fixed when the lens position changes on the image side of the fourth lens group.

  In the zoom lens disclosed in Patent Document 3, the fifth lens group includes a positive lens and a negative lens arranged on the image side thereof.

  In the zoom lenses disclosed in Patent Document 4, Patent Document 5, and Patent Document 6, the fifth lens group is composed of one positive lens.

JP-A-3-12621 JP 2003-295059 A JP 2002-365539 A JP-A-3-154014 JP-A-5-264902 Japanese Patent Laid-Open No. 7-151967

  By the way, the conventional positive / negative / positive / positive four-group zoom lens has a problem that the performance deterioration due to the eccentricity in the third lens group is remarkable, and it is difficult to obtain a stable optical performance at the time of manufacture.

  In the zoom lens disclosed in Patent Document 3, when the refractive power of the negative lens in the fifth lens group is increased, the exit pupil position approaches the image plane position, and as a result, the zoom lens is disposed in the fifth lens group. Negative distortion generated in the wide-angle end state by the negative lens cannot be corrected satisfactorily, and the third lens group has to be constituted by a plurality of lens blocks.

  In this specification, the term “lens block” means a set of lenses that can be handled as a single object, and specifically includes a single lens and a cemented lens.

  In the zoom lenses disclosed in Patent Document 4, Patent Document 5, and Patent Document 6, since the fifth lens group is composed of a single positive lens, negative distortion occurring in the wide-angle end state is corrected. Therefore, the third lens group must be composed of a plurality of lens blocks.

  The present invention solves the above-described problems, and provides a zoom lens capable of ensuring stable optical quality at the time of manufacture, in which the third lens group is configured by one lens block, and an imaging device using the zoom lens. This is the issue.

  The zoom lens according to the present invention has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A fourth lens group and a fifth lens group are arranged, and when the lens position changes from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fifth lens The group is fixed in the optical axis direction, the second lens group is moved to the image side, and the fourth lens group is moved so as to compensate for the fluctuation of the image plane position caused by the movement of the second lens group. The aperture stop is disposed in the vicinity of the third lens group, the third lens group is constituted by one lens block, the fifth lens group includes a negative part group having negative refractive power, and the negative part. Has positive refracting power that is spaced apart on the image side of the group The positive subgroup is shiftable in a direction substantially perpendicular to the optical axis, and Rp is the radius of curvature of the most object-side lens surface of the positive subgroup arranged in the fifth lens group. As a result, the conditional expression (4) −0.25 <(Rn−Rp) / (Rn + Rp) <0.2 is satisfied.

  Therefore, in the zoom lens of the present invention, the third lens group is composed of one lens block, and the positive subgroup in the fifth lens group can be shifted in a direction substantially perpendicular to the optical axis.

  The image pickup apparatus of the present invention includes the zoom lens according to another aspect of the invention, an image sensor that converts an optical image formed by the zoom lens into an electric signal, a camera shake detection unit that detects a shake of the image sensor, and the camera shake. A shake correction angle for correcting image shake due to shake of the image sensor detected by the detection means is calculated, and a positive subgroup in the fifth lens group which is a shake correction lens group is set to a position based on the shake correction angle. A camera shake control unit that sends a drive signal to the drive unit and a camera shake drive unit that shifts the positive subgroup in a direction perpendicular to the optical axis based on the drive signal are provided.

  Therefore, in the imaging apparatus of the present invention, the positive subgroup in the fifth lens group is shifted in a direction substantially perpendicular to the optical axis so as to correct camera shake during shooting.

The zoom lens according to the present invention has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A fourth lens group and a fifth lens group are arranged, and when the lens position changes from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fifth lens The group is fixed in the optical axis direction, the second lens group is moved to the image side, and the fourth lens group is moved so as to compensate for the fluctuation of the image plane position caused by the movement of the second lens group. The aperture stop is disposed in the vicinity of the third lens group, the third lens group is constituted by one lens block, the fifth lens group includes a negative part group having negative refractive power, and the negative part. Has positive refracting power that is spaced apart on the image side of the group And a positive sub group, the positive sub group is a possible shift in a direction substantially perpendicular to the optical axis, and satisfies the following conditional expression (4).
(4) -0.25 <(Rn-Rp) / (Rn + Rp) <0.2
However,
Rn: radius of curvature of the image side lens surface of the negative partial group arranged in the fifth lens group Rp: the radius of curvature of the most object side lens surface of the positive partial group arranged in the fifth lens group.

  Therefore, in the zoom lens of the present invention, it is possible to shift the image while maintaining high optical performance, and it can be configured to be small.

  The imaging device of the present invention includes the zoom lens according to another aspect of the invention, an imaging element that converts an optical image formed by the zoom lens into an electric signal, a camera shake detection unit that detects a shake of the imaging element, and a camera shake detection unit. Is used to calculate a shake correction angle for correcting image shake caused by the shake of the image sensor detected by the step S1, and to drive the positive subgroup in the fifth lens group, which is a shake correction lens group, to a position based on the shake correction angle. And a camera shake drive unit that shifts the positive subgroup in a direction substantially orthogonal to the optical axis based on the drive signal.

Therefore, in the image pickup apparatus of the present invention, the positive subgroup in the fifth lens group is shifted in a direction substantially perpendicular to the optical axis so as to detect camera shake during image capturing and correct image blur due to the camera shake. Can be made. Further, since the positive subgroup can be shifted in a direction substantially perpendicular to the optical axis and satisfies the conditional expression (4), the positive subgroup disposed in the fifth lens group is in a direction substantially orthogonal to the optical axis. The image can be shifted by shifting to a positive angle, and fluctuations in various aberrations that occur when the positive subgroup is shifted can be corrected well.

In the invention described in claim 3 , conditional expression (2) 0.15 <, where f2 is the focal length of the second lens group and fn is the focal length of the negative subgroup disposed in the fifth lens group. Since | f2 / fn | <0.6 is satisfied, downsizing and correction of distortion can be achieved in a well-balanced manner.

In the invention described in claim 4 , conditional expression (3) 2.5 <f3 / fw <where f3 is the focal length of the third lens group and fw is the focal length of the entire lens system in the wide-angle end state. 6 is satisfied, the change in the exit pupil position accompanying the change in the lens position state can be set to an appropriate value, and the negative field curvature that occurs in the wide-angle end state can be corrected well.

In the invention described in claim 2 , since the conditional expression (1) is satisfied in the above-described zoom lens of the present invention, it is possible to ensure stable performance at the time of manufacture and to correct distortion well. can do.

  The best mode for carrying out the zoom lens and the imaging apparatus of the present invention will be described below with reference to the drawings.

  The zoom lens according to the present invention has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. When the lens position changes from the wide-angle end state where the focal length is the shortest to the telephoto end state where the focal length is the longest, the first lens is formed by arranging four lens groups, the fourth lens group and the fifth lens group. Group, third lens group, and fifth lens group are fixed in the optical axis direction, the second lens group is moved to the image side, and the fourth lens group is generated in accordance with the movement of the second lens group. To compensate for the fluctuations (compensate action).

An aperture stop is disposed in the vicinity of the third lens group. The third lens group is constituted by one lens block, that is, one single lens or one cemented lens, and the fifth lens group is formed from the object side. in turn, the negative subgroup having a negative refractive power, have a positive sub group having a positive refractive power, the positive subgroup can be shifted in a direction substantially perpendicular to the optical axis.

  In the present invention, since one negative lens arranged in the negative subgroup has a feature of directing a strong concave surface toward the image side, the lens diameter of the first lens group can be reduced and the performance can be improved. I was able to make it compatible.

  Since the first lens group is originally located away from the image plane position, the lens diameter is large. Considering the size of the entire optical system, the lens diameter affects the two directions of height and width. Therefore, it is important to reduce the lens diameter of the first lens group in order to reduce the size of the optical system.

  In order to reduce the size of the first lens group, it is necessary to reduce the movement stroke of the second lens group, that is, to increase the refractive power of the second lens group.

  However, the positive, negative, positive, and positive four-group zoom lens cannot satisfactorily correct negative distortion occurring in the wide-angle end state because the second lens group is the only lens group having negative refractive power. For this reason, the third lens group is composed of a positive subgroup having a positive refractive power and a negative subgroup having a negative refractive power arranged on the image side thereof, so that negative distortion can be corrected well. It was.

  However, since the third lens group originally has a function of converging the axial light beam that is strongly diverged by the second lens group, the refractive power is strong. Therefore, if the refractive power of the negative subgroup is increased, The power of the group will also increase. As a result, the performance deterioration due to the mutual decentration of the two partial groups constituting the third lens group tends to be large, and there has been a problem that stable optical quality cannot be obtained at the time of manufacture.

  Therefore, the present invention has focused on the point that the lens group arranged farther from the aperture stop is more suitable for correcting distortion because the off-axis light beam passes away from the optical axis.

  Specifically, the fifth lens group is disposed on the image side of the fourth lens group. The fifth lens group includes a negative lens and includes a negative sub-group having a negative refractive power and a positive sub-group having a positive refractive power that is disposed on the image side with an air gap therebetween, thereby achieving a wide angle. Negative distortion generated in the end state is corrected well, the exit pupil position is moved away from the image plane position, and vignetting of the light beam by the microlens array is eliminated.

  Further, since the negative distortion can be corrected by the fifth lens group, the third lens group can be constituted by one lens block, and stable optical performance can be achieved even during manufacturing.

  Note that the fifth lens group can be constituted by a positive subgroup having a positive refractive power and a negative subgroup having a negative refractive power in order from the object side. In this case, however, the exit pupil position is the image plane position. Since it approaches, this invention is comprised as mentioned above.

In the zoom lens of the present invention, Rn is the radius of curvature of the image side lens surface of the negative portion group arranged in the fifth lens group, Da is the image side lens of the negative portion group arranged in the fifth lens group from the aperture stop. It is more desirable to satisfy the following conditional expression (1) as the distance to the surface .
(1) 0.5 <Rn / Da <1.2
The conditional expression (1) is a conditional expression that defines the shape of the negative subgroup disposed in the fifth lens group.

  When the upper limit value of conditional expression (1) is exceeded (the radius of curvature of the image side lens surface of the negative subgroup increases), the effect of correcting distortion aberration in the negative subgroup is reduced, and negative that occurs in the wide-angle end state Thus, it becomes impossible to sufficiently correct the distortion aberration.

  On the contrary, when the lower limit value of conditional expression (1) is not reached (the radius of curvature of the image side lens surface of the negative subgroup becomes small), the positive subgroup and the negative subgroup constituting the fifth lens group are inclined with respect to each other. Deterioration of the performance that occurs during the process becomes remarkably large, and it becomes difficult to obtain stable optical quality at the time of manufacture.

More preferably, the zoom lens according to the present invention satisfies the following conditional expression (2), where f2 is the focal length of the second lens group and fn is the focal length of the negative subgroup disposed in the fifth lens group.
(2) 0.15 <| f2 / fn | <0.6
Conditional expression (2) is a conditional expression that defines the focal length ratio between the negative sub-group disposed in the fifth lens group and the second lens group, and is intended to balance the downsizing and distortion correction. Conditional expression.

  When the upper limit of conditional expression (2) is exceeded (the refractive power of the second lens group is weakened, and as a result, the refractive power of the negative subgroup is strengthened), the off-axis light beam passing through the first lens group is separated from the optical axis. The entire lens system is increased in size because the lens is separated and the entire length of the lens is increased.

  Conversely, when the lower limit value of conditional expression (2) is not reached (the refractive power of the second lens group increases and as a result the refractive power of the negative subgroup weakens), negative distortion occurring in the wide-angle end state is reduced. It becomes difficult to correct well.

More preferably, the zoom lens according to the present invention satisfies the following conditional expression (3), where f3 is a focal length of the third lens unit and fw is a focal length of the entire lens system in the wide-angle end state.
(3) 2.5 <f3 / fw <6
Conditional expression (3) is a conditional expression that defines the focal length of the third lens group.

  When the upper limit value of conditional expression (3) is exceeded, the refractive power of the fourth lens group becomes strong, and the change in the exit pupil position accompanying the change in the lens position state becomes large. As a result, vignetting due to the microlens array occurs.

  If the lower limit value of conditional expression (3) is not reached, it becomes difficult to satisfactorily correct the negative curvature of field generated in the third lens group in the wide-angle end state, and the simplified configuration of the third lens group (of 1 It is impossible to achieve a lens block).

The zoom lens according to the present invention has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A fourth lens group and a fifth lens group are arranged, and when the lens position changes from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fifth lens The group is fixed in the optical axis direction, the second lens group is moved to the image side, and the fourth lens group is moved so as to compensate for the fluctuation of the image plane position caused by the movement of the second lens group. The third lens group is composed of one lens block, and the fifth lens group is a negative part group having a negative refractive power and a positive part disposed at an image side of the negative part group with an air gap. A positive subgroup having a refractive power of A shiftable straight direction, satisfies the following conditional expression (4).
(4) -0.25 <(Rn-Rp) / (Rn + Rp) <0.2
However,
Rn: radius of curvature of the image side lens surface of the negative partial group arranged in the fifth lens group Rp: the radius of curvature of the most object side lens surface of the positive partial group arranged in the fifth lens group.

  In the zoom lens according to the present invention, the image can be shifted by shifting the positive subgroup disposed in the fifth lens group in a direction substantially perpendicular to the optical axis.

  By the way, conventionally, there has been proposed a zoom lens capable of shifting an image by shifting an entire lens group constituting the zoom lens or a part thereof in a direction substantially perpendicular to the optical axis. . Among them, it is possible to shift the image by shifting the entire third lens group arranged in the vicinity of the aperture stop or a part of the third lens group in a direction substantially perpendicular to the optical axis. There is something. In such a zoom lens, since the lens group in the vicinity of the aperture stop is shifted, the shift drive mechanism and the drive mechanism of the aperture stop are likely to interfere with each other, which hinders downsizing. At the same time, since the second lens group and the fourth lens group that are movable in the optical axis direction are also arranged in the vicinity, there is a problem that it is very difficult to reduce the size.

  Therefore, all or one of the fifth lens groups that have no fear of interference with the driving mechanism of the aperture stop and the movable driving mechanisms of the second lens group and the fourth lens group and have a long back focus in the vicinity thereof. It is conceivable to shift the part.

  By the way, when the fifth lens group is composed of one negative subgroup, if the refractive power is weak, the blur correction coefficient (= image shift amount / lens shift amount) is low, so the lens shift amount becomes extremely large. This will increase the size of the drive mechanism. Further, when the negative refractive power is increased, the off-axis light beam passing through the fourth lens group is greatly separated from the optical axis, and the entire lens length is extremely increased.

  On the other hand, when the fifth lens group is composed of one positive subgroup, if the refractive power is weak, the blur correction coefficient is low, so the lens shift amount becomes extremely large and the drive mechanism becomes large. In addition, when the positive refractive power is increased, the refractive power of the fourth lens group is weakened, so that the amount of movement of the fourth lens group necessary for the compensating action is increased, and the total length of the lens is increased.

Therefore, in the zoom lens according to the present invention , the fifth lens group includes a negative subgroup having a negative refractive power and a positive subgroup located on the image side of the negative subgroup and having a positive refractive power. By shifting, both a high blur correction coefficient and a reduction in the overall lens length are achieved. As a result, variations in various aberrations that occur when the image is shifted are small, and high optical performance can be maintained.

In the zoom lens of the present invention, by utilizing the point that the height of the off-axis light beam passing through the fifth lens group fixed in the optical axis direction is approximately constant regardless of the change in the lens position state, The fluctuation of off-axis aberration that occurs when shifting is corrected well.

  In addition, since the subject image is received by the image sensor, the exit pupil position is away from the image plane position, and it is easy to suppress fluctuations in distortion that occur when the lens is shifted, and high performance can be achieved.

  As a result, it is possible to reduce the interference between the drive mechanisms, which is a problem in the conventional method in which the entire third lens group or a part of the third lens group is shifted, and to reduce the size of the entire lens barrel.

  In another zoom lens of the present invention, in order to satisfactorily correct variations in various aberrations that occur when the positive subgroup is shifted, the above conditional expression (4) −0.25 <(Rn−Rp) / ( It is desirable that Rn + Rp) <0.2.

  Conditional expression (4) is a conditional expression that defines the shape of the air gap formed between the negative subgroup and the positive subgroup arranged in the fifth lens group.

  If the upper limit value of conditional expression (4) is exceeded or falls below the lower limit value, it will be difficult to suppress fluctuations in field curvature that occur when the positive subgroup is shifted. When the positive subgroup is shifted, the optical path of the principal ray from the aperture stop to the image plane position changes. However, when the change in the optical path length at the top and bottom of the screen increases, the fluctuation of the field curvature increases. In the present invention, the radius of curvature of the image side lens surface of the negative subgroup with the air gap interposed therebetween is made closer to the radius of curvature of the object side lens surface of the positive subgroup (when the same radius of curvature is satisfied, conditional expression (4) 0), the variation in field curvature that occurs when the positive subgroup is shifted is suppressed, and high performance is realized.

  In addition, by satisfying the conditional expression (1) and the conditional expression (4) at the same time, the negative distortion occurring in the wide-angle end state is corrected well, and the positive subgroup is generated. It is possible to suppress variations in field curvature.

  In the zoom lens of the present invention, the second positive part group is arranged on the image side of the negative part group constituting the fifth lens group and the (first) positive part group, and the first positive part group is By shifting in a direction substantially perpendicular to the optical axis, both a high blur correction coefficient and a low image plane movement coefficient can be achieved.

  The blur correction coefficient relates to the lateral magnification of the shift lens group, and represents the ratio of the image shift amount to the lens shift amount when shifted in the direction perpendicular to the optical axis. The image plane movement coefficient relates to the vertical magnification of the shift lens group, and represents the ratio of the variation amount of the image plane position to the lens movement amount when moving in the optical axis direction.

  When the fifth lens group is composed of only the negative subgroup and the positive subgroup, and the positive subgroup is shifted, if the blur correction coefficient is increased, the image plane movement coefficient is also increased. For this reason, when the shift lens group is slightly displaced in the optical axis direction, the image is recorded out of focus. When this displacement amount is suppressed by the drive mechanism, there is no problem even when the image plane movement coefficient is high. In order to reduce the image plane movement coefficient in the optical system and prevent the image from being blurred even if the shift lens group is slightly displaced in the optical axis direction, it is effective to arrange the second positive subgroup.

  In the zoom lens of the present invention, in order to obtain better optical performance in the telephoto end state, the first lens unit is sequentially joined from the object side, and a cemented lens of a meniscus negative lens and a positive lens having a convex surface facing the object side. It is desirable to construct a meniscus positive lens having a convex surface facing the object side.

  The second lens group is preferably composed of three lenses: a negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a positive lens having a convex surface facing the object side. By separating the aberration correction function so that the negative meniscus lens is well corrected for off-axis aberrations occurring in the wide-angle end state, and the biconcave lens and the positive lens are well corrected for on-axis aberrations. Better optical performance can be obtained. In particular, by using a biconcave lens and a positive lens as a cemented lens, stable optical quality can be obtained even during manufacturing.

  Furthermore, it is desirable that the fourth lens group is composed of one lens block in order to simplify the configuration. In order to further reduce the weight, it is desirable to use a single positive lens. In particular, in order to improve performance, it is desirable to use a positive cemented lens composed of a positive lens and a negative lens.

  Furthermore, higher optical performance can be realized by using an aspheric lens. In particular, by introducing an aspheric surface into the third lens group or the fourth lens group, the central performance can be further improved. Further, by using an aspheric lens for the second lens group, it is possible to satisfactorily correct coma variation due to the angle of view generated in the wide-angle end state.

  It goes without saying that higher optical performance can be obtained by using a plurality of aspheric surfaces in one optical system.

  Furthermore, it is of course possible to arrange a low-pass filter on the image side of the lens system in order to prevent the occurrence of moire fringes or an infrared cut filter in accordance with the spectral sensitivity characteristics of the light receiving element.

  Embodiments to which the zoom lens of the present invention is applied and numerical examples in which specific numerical values are applied to these embodiments will be described below.

  In addition, the aspherical shape adopted in each numerical example is represented by the following equation (1).

  Here, y is the height from the optical axis, x is the sag amount, c is the curvature, κ is the conic constant, A, B,... Are aspherical coefficients.

  FIG. 1 shows the refractive power distribution of the zoom lens according to each embodiment. In order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a negative A third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power are arranged to change from the wide-angle end state to the telephoto end state. During zooming, the air gap between the first lens group G1 and the second lens group G2 increases, and the air gap between the second lens group G2 and the third lens group G3 decreases. The lens group G2 moves to the image side. At this time, the first lens group G1, the third lens group G3, and the fifth lens group G5 are fixed, and the fourth lens group G4 corrects the variation of the image plane position accompanying the movement of the second lens group G2. And move to the object side when focusing on a short distance.

  FIG. 2 shows a lens configuration of the zoom lens 1 according to the first embodiment. The first lens group G1 includes a cemented lens L11 of a meniscus negative lens having a convex surface directed toward the object side and a positive lens having a convex surface directed toward the object side, and a positive lens L12 having a convex surface directed toward the object side. The lens group G2 includes a negative lens L21 having a concave surface facing the image side and a cemented lens L22 of a biconcave negative lens and a positive lens having a convex surface facing the object side. The third lens group G3 includes a biconvex lens and a concave lens. The fourth lens group G4 is composed of a cemented lens L4 of a biconvex lens and a concave lens, and the fifth lens group G5 is a biconcave lens L51, a biconvex lens L52, and a negative lens with a concave surface facing the image side. The lens L53 and the biconvex lens L54 are used.

  In the fifth lens group G5, the biconcave lens L51 functions as a negative subgroup, the negative lens L53 having a concave surface facing the biconvex lens L52 and the image side and the biconvex lens L54 function as a positive subgroup, and the biconvex lens L52 and the concave surface on the image side. The image can be shifted by shifting the directed negative lens L53 in a direction substantially perpendicular to the optical axis. That is, the biconvex lens L52 and the negative lens L53 are a first positive subgroup, and the biconvex lens L54 is a second positive subgroup.

  An aperture stop S is disposed near the object side of the third lens group G3, and a low-pass filter LPF is disposed between the fifth lens group G5 and the image plane IMG.

  Table 1 shows values of specifications of Numerical Example 1 in which specific numerical values are applied to the first embodiment. The surface number in the following specification table indicates the i-th surface from the object side, the radius of curvature indicates the on-axis radius of curvature of the surface, and the refractive index with respect to the d-line (λ = 587.6 nm) of the surface. The Abbe number indicates the value for the d-line of the surface, f indicates the focal length, FNO indicates the F number, and 2ω indicates the angle of view. A curvature radius of 0 indicates a plane.

The twelfth surface, the twentieth surface and the twenty-first surface are aspherical surfaces. Therefore, Table 2 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A, B, C, and D together with the conic constant κ in Numerical Example 1. In Table 2 and the following tables showing aspheric coefficients, “E-i” represents an exponential expression with a base of 10, that is, “10- ⁱ ”. For example, “0.26029E-05” 0.26029 × 10 ⁻⁵ ”.

  When the lens position changes from the wide-angle end state to the telephoto end state, the surface distance D5 between the first lens group G1 and the second lens group G2, and the distance between the second lens group G2 and the aperture stop S are changed. The surface distance D10, the surface distance D14 between the third lens group G3 and the fourth lens group G4, and the surface distance D17 between the fourth lens group G4 and the fifth lens group G5 change. Therefore, Table 3 shows the above-described surface spacing, blur correction coefficient, and image plane movement in Numerical Example 1 in the wide-angle end state (f = 1.000), the intermediate focal length state (f = 1.998), and the telephoto end state (F = 4.703). Indicates the coefficient.

  Table 4 shows values corresponding to the conditional expressions (1) to (4) in the numerical example 1.

  FIGS. 3 to 5 show various aberration diagrams in the infinite focus state in Numerical Example 1, FIG. 3 is a wide angle end state (f = 1.000), FIG. 4 is an intermediate focal length state (f = 1.998), FIG. 5 shows various aberrations in the telephoto end state (f = 4.703).

  3 to 5, the solid line in the spherical aberration diagram indicates spherical aberration, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, A indicates a half field angle, and y indicates an image height.

  6 to 8 show lateral aberration diagrams in the lens shift state corresponding to 0.5 degrees in the infinitely focused state in Numerical Example 1, respectively, FIG. 6 is a wide-angle end state (f = 1.000), and FIG. FIG. 8 is a lateral aberration diagram in the intermediate focal length state (f = 1.998), and FIG. 8 in the telephoto end state (f = 4.703). In the lateral aberration diagram, A indicates a half field angle, and y indicates an image height.

  From the aberration diagrams, it is clear that Numerical Example 1 has excellent image forming performance with various aberrations corrected well.

  FIG. 9 is a diagram illustrating a lens configuration of the zoom lens 2 according to the second embodiment. The first lens group G1 includes a cemented lens L11 of a meniscus negative lens having a convex surface directed toward the object side and a positive lens having a convex surface directed toward the object side, and a positive lens L12 having a convex surface directed toward the object side. The lens group G2 includes a negative lens L21 having a concave surface facing the image side and a cemented lens L22 of a biconcave negative lens and a positive lens having a convex surface facing the object side. The third lens group G3 includes a biconvex lens and a concave lens. The fourth lens group G4 includes a biconvex lens L4, and the fifth lens group G5 includes a biconcave lens L51, a biconvex lens L52, a negative lens L53 having a concave surface directed toward the image side, and a biconvex lens L54. Consists of.

  In the fifth lens group G5, the biconcave lens L51 functions as a negative subgroup, the negative lens L53 having a concave surface facing the biconvex lens L52 and the image side and the biconvex lens L54 function as a positive subgroup, and the biconvex lens L52 and the concave surface on the image side. The image can be shifted by shifting the directed negative lens L53 in a direction substantially perpendicular to the optical axis. That is, the biconvex lens L52 and the negative lens L53 are a first positive subgroup, and the biconvex lens L54 is a second positive subgroup.

  An aperture stop S is disposed near the object side of the third lens group G3, and a low-pass filter LPF is disposed between the fifth lens group G5 and the image plane IMG.

  Table 5 shows values of specifications of Numerical Example 2 in which specific numerical values are applied to the second embodiment.

  The twelfth, nineteenth and twentieth surfaces are aspherical. Accordingly, the fourth-order, sixth-order, eighth-order and tenth-order aspheric coefficients A, B, C and D of these surfaces in Numerical Example 2 are shown in Table 6 together with the conic constant κ.

  When the lens position changes from the wide-angle end state to the telephoto end state, the surface distance D5 between the first lens group G1 and the second lens group G2, and the distance between the second lens group G2 and the aperture stop S are changed. The surface distance D10, the surface distance D14 between the third lens group G3 and the fourth lens group G4, and the surface distance D16 between the fourth lens group G4 and the fifth lens group G5 change. Therefore, Table 7 shows the above-described surface spacing, blur correction coefficient, and image plane movement in Numerical Example 2 in the wide-angle end state (f = 1.000), the intermediate focal length state (f = 2.015), and the telephoto end state (F = 4.703). Indicates the coefficient.

  Table 8 shows values corresponding to the conditional expressions (1) to (4) in the numerical example 2.

  10 to 12 show various aberration diagrams in the infinite focus state in Numerical Example 2, FIG. 10 is a wide-angle end state (f = 1.000), FIG. 11 is an intermediate focal length state (f = 2.015), and FIG. FIG. 12 shows various aberration diagrams in the telephoto end state (f = 4.703).

  10 to 12, the solid line in the spherical aberration diagram indicates the spherical aberration, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, A indicates a half field angle, and y indicates an image height.

  FIGS. 13 to 15 show lateral aberration diagrams in the lens shift state corresponding to 0.5 degrees in the infinitely focused state in Numerical Example 2, respectively, FIG. 13 shows the wide-angle end state (f = 1.000), and FIG. FIG. 15 is a transverse aberration diagram in the intermediate focal length state (f = 2.015), and FIG. 15 in the telephoto end state (f = 4.703). In the lateral aberration diagram, A indicates a half field angle, and y indicates an image height.

  From each aberration diagram, it is clear that Numerical Example 2 has excellent imaging performance with various aberrations corrected well.

  FIG. 16 is a diagram illustrating a lens configuration according to the third embodiment. The first lens group G1 includes a cemented lens L11 of a meniscus negative lens having a convex surface directed toward the object side and a positive lens having a convex surface directed toward the object side, and a positive lens L12 having a convex surface directed toward the object side. The lens group G2 includes a negative lens L21 having a concave surface facing the image side and a cemented lens L22 of a biconcave negative lens and a positive lens having a convex surface facing the object side, and the third lens group G3 is convex on the object side. The fourth lens group G4 is composed of a cemented lens L4 of a biconvex lens and a negative lens having a convex surface facing the image side, and the fifth lens group G5 includes a biconcave lens L51 and a biconvex lens L52. The negative lens L53 and the biconvex lens L54 having a concave surface facing the image side.

  In the fifth lens group G5, the biconcave lens L51 functions as a negative subgroup, the negative lens L53 having a concave surface facing the biconvex lens L52 and the image side and the biconvex lens L54 function as a positive subgroup, and the biconvex lens L52 and the concave surface on the image side. The image can be shifted by shifting the directed negative lens L53 in a direction substantially perpendicular to the optical axis. That is, the biconvex lens L52 and the negative lens L53 are a first positive subgroup, and the biconvex lens L54 is a second positive subgroup.

  An aperture stop S is disposed near the object side of the third lens group G3, and a low-pass filter LPF is disposed between the fifth lens group G5 and the image plane IMG.

  Table 9 shows the values of specifications of Numerical Example 3 in which specific numerical values are applied to the third embodiment.

  The twelfth, nineteenth and twentieth surfaces are aspherical. Therefore, Table 10 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A, B, C, and D in Numerical Example 3 together with the conic constant κ.

  When the lens position changes from the wide-angle end state to the telephoto end state, the surface distance D5 between the first lens group G1 and the second lens group G2, and the distance between the second lens group G2 and the aperture stop S are changed. The surface distance D10, the surface distance D13 between the third lens group G3 and the fourth lens group G4, and the surface distance D16 between the fourth lens group G4 and the fifth lens group G5 change. Therefore, Table 11 shows the above-described surface spacing, blur correction coefficient, and image plane movement in Numerical Example 3 in the wide-angle end state (f = 1.000), the intermediate focal length state (f = 2.004), and the telephoto end state (F = 4.703). Indicates the coefficient.

  Table 12 shows values corresponding to the conditional expressions (1) to (4) in the numerical example 3.

  FIGS. 17 to 19 show various aberration diagrams of Numerical Example 3 in the infinite focus state, FIG. 17 is a wide angle end state (f = 1.000), FIG. 18 is an intermediate focal length state (f = 2.004), FIG. 19 shows various aberrations in the telephoto end state (f = 4.703).

  In each aberration diagram of FIGS. 17 to 19, the solid line in the spherical aberration diagram indicates the spherical aberration, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, A indicates a half field angle, and y indicates an image height.

  20 to 22 show lateral aberration diagrams in the lens shift state corresponding to 0.5 degrees in the infinitely focused state in Numerical Example 3, respectively, FIG. 20 is a wide-angle end state (f = 1.000), and FIG. FIG. 22 is a lateral aberration diagram in the intermediate focal length state (f = 2.004), and FIG. 22 in the telephoto end state (f = 4.703). In the lateral aberration diagram, A indicates a half field angle, and y indicates an image height.

  From each aberration diagram, it is clear that Numerical Example 3 has excellent imaging performance with various aberrations corrected well.

  FIG. 23 is a diagram illustrating a lens configuration of the zoom lens 4 according to the fourth embodiment. The first lens group G1 includes a cemented lens L11 of a meniscus negative lens having a convex surface directed toward the object side and a positive lens having a convex surface directed toward the object side, and a positive lens L12 having a convex surface directed toward the object side. The lens group G2 includes a negative lens L21 having a concave surface facing the image side, and a cemented lens L22 of a biconcave negative lens and a positive lens having a convex surface facing the object side. The third lens group G3 includes a biconvex lens L3. The fourth lens group G4 includes a cemented lens L4 of a biconvex lens and a negative lens having a convex surface facing the image side, and the fifth lens group G5 includes a negative lens L51 and a biconvex lens having a concave surface facing the image side. It is constituted by a cemented positive lens L52 with a concave lens.

  In the fifth lens group G5, the negative lens L51 functions as a negative partial group, and the cemented positive lens L52 functions as a positive partial group. The fifth lens group G5 shifts the image by shifting the cemented positive lens L52 in a direction substantially perpendicular to the optical axis. Is possible.

  An aperture stop S is disposed near the object side of the third lens group G3, and a low-pass filter LPF is disposed between the fifth lens group G5 and the image plane IMG.

  Table 13 shows values of specifications of Numerical Example 4 in which specific numerical values are applied to the fourth embodiment.

  The twelfth and nineteenth surfaces are aspherical surfaces. Therefore, Table 14 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients A, B, C, and D in Numerical Example 4 together with the conic constant κ.

  When the lens position changes from the wide-angle end state to the telephoto end state, the surface distance D5 between the first lens group G1 and the second lens group G2, and the distance between the second lens group G2 and the aperture stop S are changed. The surface distance D10, the surface distance D13 between the third lens group G3 and the fourth lens group G4, and the surface distance D16 between the fourth lens group G4 and the fifth lens group G5 change. Therefore, Table 15 shows the above-described surface spacing, blur correction coefficient, and image plane movement in Numerical Example 4 in the wide-angle end state (f = 1.000), the intermediate focal length state (f = 1.994), and the telephoto end state (F = 4.704). Indicates the coefficient.

  Table 16 shows values corresponding to the conditional expressions (1) to (4) in the numerical example 4.

  FIGS. 24 to 26 show various aberration diagrams of Numerical Example 4 in the infinite focus state, FIG. 24 is a wide-angle end state (f = 1.000), FIG. 25 is an intermediate focal length state (f = 1.944), FIG. 26 shows various aberration diagrams in the telephoto end state (f = 4.704).

  24 to 26, the solid line in the spherical aberration diagram indicates the spherical aberration, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, A indicates a half field angle, and y indicates an image height.

  27 to 29 show lateral aberration diagrams in the lens shift state corresponding to 0.5 degrees in the infinitely focused state in Numerical Example 4, respectively, FIG. 27 is the wide-angle end state (f = 1.000), and FIG. FIG. 29 is a lateral aberration diagram in the intermediate focal length state (f = 1.944), and FIG. 29 in the telephoto end state (f = 4.704). In the lateral aberration diagram, A indicates a half field angle, and y indicates an image height.

  From the respective aberration diagrams, it is clear that Numerical Example 4 has excellent imaging performance with various aberrations corrected well.

  FIG. 30 shows an embodiment in which the imaging apparatus of the present invention and another imaging apparatus of the present invention are applied.

    The imaging apparatus 10 includes a zoom lens 20 and includes an imaging element 30 that converts an optical image formed by the zoom lens 20 into an electrical signal. For example, a device using a photoelectric conversion device such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) can be used as the image pickup device 30. The zoom lens 20 can be applied to the zoom lens according to the present invention and another present invention. In FIG. 30, the lens group of the zoom lens 1 according to the first embodiment shown in FIG. It is shown in simplified form. Of course, not only the zoom lens 1 according to the first embodiment, but also the zoom lenses 2 to 4 according to the second to fourth embodiments and other embodiments than those shown in this specification. The zoom lens according to the present invention and another zoom lens according to the present invention can be used.

  The electrical signal formed by the image pickup device 30 is sent to the control circuit 50 by the video separation circuit 40, and the video signal is sent to the video processing circuit. The signal sent to the video processing circuit is processed into a form suitable for the subsequent processing, and is subjected to various processes such as display by a display device, recording on a recording medium, and transfer by a communication means.

  For example, an operation signal from the outside such as an operation of a zoom button is input to the control circuit 50, and various processes are performed according to the operation signal. For example, when a zooming command by the zoom button is input, the driving units 61 and 71 are operated via the driver circuits 60 and 70 to set the lens groups G2 and G4 to a predetermined state in order to set the focal length state based on the command. Move to position. Position information of the lens groups GR2 and GR4 obtained by the sensors 62 and 72 is input to the control circuit 50 and is referred to when command signals are output to the driver circuits 60 and 70. The control circuit 50 checks the focus state based on the signal sent from the video separation circuit 40 and operates the drive unit 71 via the driver circuit 70 so as to obtain the optimum focus state. The position of the four lens group G4 is controlled.

  The imaging device 10 has a camera shake correction function. For example, when a shake detection unit 80, for example, a gyro sensor detects a shake of the image sensor 30 due to a press of a shutter release button, a signal from the shake detection unit 80 is input to the control circuit 50, and the control circuit 50 A shake correction angle for compensating for shake of the image due to shake is calculated. In order to set the positive subgroup PP in the fifth lens group G5 to a position based on the calculated shake correction angle, the drive unit 91 is operated via the driver circuit 90 so that the positive subgroup PP is perpendicular to the optical axis. Move in any direction. The position of the positive subgroup PP is detected by a sensor 92, and the position information of the positive subgroup PP obtained by the sensor 92 is input to the control circuit 50 and a command signal is sent to the driver circuit 90. To be referenced.

  The imaging device 10 described above can take various forms as a specific product. For example, the present invention can be widely applied as a camera unit of a digital input / output device such as a digital still camera, a digital video camera, a mobile phone incorporating a camera, and a PDA (Personal Digital Assistant) incorporating a camera.

  It should be noted that the specific shapes and numerical values of the respective parts shown in the respective embodiments and numerical examples described above are merely examples of the implementation performed in carrying out the present invention, and the present invention is thereby limited. The technical scope of the invention should not be limitedly interpreted.

It is a figure which shows the propriety arrangement | positioning of the zoom lens of this invention, and the propriety of each lens group at the time of zooming. It is a figure which shows the lens structure of the zoom lens concerning 1st Embodiment. FIGS. 4 to 8 show various aberration diagrams of Numerical Example 1 in which specific numerical values are applied to the first embodiment. This diagram shows spherical aberration, astigmatism, distortion aberration and the like in the wide-angle end state. It shows coma aberration. It shows spherical aberration, astigmatism, distortion and coma in the intermediate focal length state. It shows spherical aberration, astigmatism, distortion and coma in the telephoto end state. This shows lateral aberration in a lens shift state corresponding to 0.5 degrees in the wide-angle end state. This shows lateral aberration in a lens shift state equivalent to 0.5 degrees in the intermediate focal length state. 3 shows lateral aberration in a lens shift state corresponding to 0.5 degrees in the telephoto end state. It is a figure which shows the lens structure of the zoom lens concerning 2nd Embodiment. FIGS. 11 to 15 show various aberration diagrams of Numerical Example 2 in which specific numerical values are applied to the second embodiment. FIG. 11 shows spherical aberration, astigmatism, distortion aberration, and the like in the wide-angle end state. It shows coma aberration. It shows spherical aberration, astigmatism, distortion and coma in the intermediate focal length state. It shows spherical aberration, astigmatism, distortion and coma in the telephoto end state. This shows lateral aberration in a lens shift state corresponding to 0.5 degrees in the wide-angle end state. This shows lateral aberration in a lens shift state equivalent to 0.5 degrees in the intermediate focal length state. 3 shows lateral aberration in a lens shift state corresponding to 0.5 degrees in the telephoto end state. It is a figure which shows the lens structure of the zoom lens concerning 3rd Embodiment. FIGS. 18 to 22 show various aberration diagrams of Numerical Example 3 in which specific numerical values are applied to the third embodiment. This diagram shows spherical aberration, astigmatism, distortion aberration and the like in the wide-angle end state. It shows coma aberration. It shows spherical aberration, astigmatism, distortion and coma in the intermediate focal length state. It shows spherical aberration, astigmatism, distortion and coma in the telephoto end state. This shows lateral aberration in a lens shift state corresponding to 0.5 degrees in the wide-angle end state. This shows lateral aberration in a lens shift state equivalent to 0.5 degrees in the intermediate focal length state. 3 shows lateral aberration in a lens shift state corresponding to 0.5 degrees in the telephoto end state. It is a figure which shows the lens structure of the zoom lens concerning 4th Embodiment. FIG. 25 to FIG. 29 show various aberration diagrams of Numerical Example 4 in which specific numerical values are applied to the fourth embodiment. This diagram shows spherical aberration, astigmatism, distortion aberration and the like in the wide-angle end state. It shows coma aberration. It shows spherical aberration, astigmatism, distortion and coma in the intermediate focal length state. It shows spherical aberration, astigmatism, distortion and coma in the telephoto end state. This shows lateral aberration in a lens shift state corresponding to 0.5 degrees in the wide-angle end state. This shows lateral aberration in a lens shift state equivalent to 0.5 degrees in the intermediate focal length state. 3 shows lateral aberration in a lens shift state corresponding to 0.5 degrees in the telephoto end state. It is a block diagram which shows embodiment of the imaging device of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Zoom lens, 2 ... Zoom lens, 3 ... Zoom lens, 4 ... Zoom lens, G1 ... 1st lens group, G2 ... 2nd lens group, G3 ... 3rd lens group, G4 ... 4th lens group, G5 ... 5th lens group, 10 ... imaging device, 20 ... zoom lens, 30 ... imaging element, 80 ... camera shake detecting means, 50 ... control circuit (camera shake control means), 91 ... drive unit (camera shake drive unit)

Claims (5)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and A fifth lens group,
When the lens position changes from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fifth lens group are fixed in the optical axis direction, and the second lens group is on the image side. And the fourth lens group is moved so as to compensate for fluctuations in the image plane position caused by the movement of the second lens group,
An aperture stop is disposed in the vicinity of the third lens group,
The third lens group includes one lens block,
The fifth lens group includes a negative subgroup having a negative refractive power, and a positive subgroup having a positive refractive power that is disposed on the image side of the negative subgroup at an air interval,
The positive subgroup can be shifted in a direction substantially perpendicular to the optical axis,
A zoom lens satisfying the following conditional expression (4):
(4) -0.25 <(Rn-Rp) / (Rn + Rp) <0.2
However,
Rn: radius of curvature of the image side lens surface of the negative partial group arranged in the fifth lens group Rp: the radius of curvature of the most object side lens surface of the positive partial group arranged in the fifth lens group. The zoom lens according to claim 1.
A zoom lens satisfying the following conditional expression (1):
(1) 0.5 <Rn / Da <1.2
However,
Da: Distance from the aperture stop to the image side lens surface of the negative sub-group disposed in the fifth lens group. The zoom lens according to claim 1.
A zoom lens satisfying the following conditional expression (2):
(2) 0.15 <| f2 / fn | <0.6
However,
f2: focal length of the second lens group fn: focal length of the negative subgroup disposed in the fifth lens group. The zoom lens according to claim 3.
A zoom lens satisfying the following conditional expression (3):
(3) 2.5 <f3 / fw <6
However,
f3: focal length of the third lens unit fw: the focal length of the entire lens system in the wide-angle end state. A zoom lens, an image sensor that converts an optical image formed by the zoom lens into an electrical signal, a camera shake detection unit that detects a shake of the image sensor, and an image shake caused by the shake of the image sensor detected by the camera shake detection unit Camera shake control means for calculating a shake correction angle for correction and sending a drive signal to the drive unit so that the shake correction lens group is positioned based on the shake correction angle, and the shake correction lens group based on the drive signal An image pickup apparatus including a camera shake driving unit that shifts the lens in a direction substantially orthogonal to the optical axis,
The zoom lens includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a first lens group having a positive refractive power. 4 lens group and 5th lens group are arranged.
When the lens position changes from the wide-angle end state to the telephoto end state, the first lens group, the third lens group, and the fifth lens group are fixed in the optical axis direction, and the second lens group is on the image side. And the fourth lens group is moved so as to compensate for fluctuations in the image plane position caused by the movement of the second lens group,
An aperture stop is disposed in the vicinity of the third lens group,
The third lens group includes one lens block,
The fifth lens group includes a negative subgroup having a negative refractive power, and a positive subgroup having a positive refractive power that is disposed on the image side of the negative subgroup at an air interval,
The positive part group functions as a blur correction lens group that can be shifted in a direction substantially perpendicular to the optical axis,
An image pickup apparatus satisfying the following conditional expression (4):
(4) -0.25 <(Rn-Rp) / (Rn + Rp) <0.2
However,
Rp: The radius of curvature of the most object-side lens surface of the positive subgroup disposed in the fifth lens group.

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