JP2012103626A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens capable of reducing occurrence of chromatic aberration of magnification and further correcting chromatic aberration of magnification and axial color aberration at the same time.SOLUTION: A zoom lens 100 comprises: a fist refractive power variable face 101b arranged on the object side of a diaphragm 103; a second refractive power various face 105b arranged on the image face side of the diaphragm 103 for causing chromatic aberration of magnification, which has a symbol same as a symbol of the first refractive power variable face 101b; and a third refractive power variable face 105a for causing chromatic aberration of magnification, which has a symbol different from symbols of the first and second refractive power variable faces 101b and 105b. In a case where the third refractive power variable face 105a is arranged on the object side of the diaphragm 103, the chromatic aberration of magnification at the wide angle end of the first refractive power variable face 101b is LATor where the third refractive power various face 105a is arranged on the image face side of the diaphragm 103, a chromatic aberration of magnification at the wide angle end of the second refractive power various face 105b is LAT, and the chromatic aberration of magnification at the wide angle end of the third refractive power various face 105a is LAT, a condition expressed by |LAT|<|LAT| is satisfied.

Description

  The present invention relates to a zoom lens including a refractive power variable element.

  2. Description of the Related Art Conventionally, a refractive power variable element (variable focus element) that can change the refractive power by controlling the shape of a liquid interface is known. For example, Patent Document 1 discloses a variable focus lens that can deform a contact surface (interface) between a conductive liquid and an insulating liquid having different refractive indexes. Patent Document 2 discloses a zoom lens that uses two refractive power variable elements and has no relative movement of the lens. On the other hand, normally, when zooming is performed using a refractive power variable element, correction conditions for chromatic aberration and Petzval sum may be lost, and chromatic aberration and curvature of field may increase. Therefore, Patent Document 3 discloses an optical system that corrects chromatic aberration or curvature of field by combining a plurality of refractive power variable elements (liquid lenses). Furthermore, Patent Document 4 discloses an optical system that individually corrects longitudinal chromatic aberration and lateral chromatic aberration by using refractive power variable elements having substantially the same refractive index and different only dispersion.

JP 2006-178469 A Special table 2008-541184 International Publication No. 2006/103290 Japanese Patent Publication No.62-78521

  In the zoom lens disclosed in Patent Document 2, the chromatic aberration is corrected by adjusting the chromatic aberration generated by the refractive power variable element using the refractive power variable elements arranged before and after the chromatic aberration. However, this zoom lens can correct either axial chromatic aberration or lateral chromatic aberration, but it is difficult to correct both chromatic aberrations simultaneously. Patent Document 3 describes a description based on chromatic aberration and Petzval sum, and in particular, in chromatic aberration correction, describes a mathematical expression for correcting axial chromatic aberration. However, a specific configuration relating to chromatic aberration correction is not described, and in particular, correction of lateral chromatic aberration is not described. Furthermore, Patent Document 4 discloses a configuration that can correct lateral chromatic aberration and axial chromatic aberration, but does not indicate what correction should be performed and in what location. Further, the chromatic aberration to be corrected by this optical system is caused by the movement of the zoom lens, and a description of a specific configuration for correcting chromatic aberration generated by fluctuation of the refractive power itself, such as a refractive power variable element. There is no.

  The present invention has been made in view of such a situation, and includes a refractive power variable element that reduces the occurrence of lateral chromatic aberration and further enables simultaneous correction of lateral chromatic aberration and axial chromatic aberration. An object is to provide a zoom lens.

In order to solve the above-described problems, the present invention generates a first refractive power variable surface disposed on the object side of a diaphragm, and a chromatic aberration of magnification having the same sign as that of the first refractive power variable surface, so that an image of the diaphragm is obtained. A zoom lens including a second refractive power variable surface disposed on the surface side, a first refractive power variable surface and a third refractive power variable surface that causes lateral chromatic aberration of different sign, When the third refractive power variable surface is arranged on the object side of the stop, the lateral chromatic aberration at the wide angle end of the first refractive power variable surface or the third refractive power variable surface is on the image surface side of the stop. When arranged, when the lateral chromatic aberration at the wide-angle end of the second refractive power variable surface is LAT ₁ , while the lateral chromatic aberration at the wide-angle end of the third refractive power variable surface is LAT ₂ ,
│LAT ₁ │ <│LAT ₂ │
It satisfies the following condition.

  According to the present invention, it is possible to provide a zoom lens that can reduce the occurrence of lateral chromatic aberration and that can simultaneously correct lateral chromatic aberration and axial chromatic aberration.

1 is a lens schematic diagram of a zoom lens according to a first embodiment of the present invention. It is the schematic which shows the structure of the refractive index variable element which concerns on 1st Embodiment. 1 is a conceptual diagram of a zoom lens according to a first embodiment. It is a figure which shows each surface number of the zoom lens which concerns on 1st Embodiment. It is a longitudinal aberration diagram showing the effect of the zoom lens according to the first embodiment. It is a lateral aberration diagram showing the effect of the zoom lens according to the first embodiment. It is a lens schematic diagram of a zoom lens according to a second embodiment of the present invention. It is a figure which shows each surface number of the zoom lens which concerns on 2nd Embodiment. It is a longitudinal aberration diagram showing the effect of the zoom lens according to the second embodiment. It is a lateral aberration diagram showing the effect of the zoom lens according to the second embodiment. It is a lens schematic diagram of a zoom lens according to a third embodiment of the present invention. It is a figure which shows each surface number of the zoom lens which concerns on 3rd Embodiment. It is a longitudinal aberration diagram showing the effect of the zoom lens according to the third embodiment. It is a lateral aberration diagram showing the effect of the zoom lens according to the third embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(First embodiment)
First, the zoom lens according to the first embodiment of the present invention will be described. FIG. 1 is a lens cross-sectional view of a zoom lens according to the present embodiment. 1A shows a lens cross-sectional view of the zoom lens 100 at the wide-angle end (Wide), and FIG. 1B shows a lens cross-sectional view of the zoom lens 100 at the telephoto end (Tele). The zoom lens 100 includes, in order from the object (subject) side, a first refractive power variable element 101, a first solid lens 102, a diaphragm 103, a second solid lens 104, a second refractive power variable element 105, And a third solid lens 106. As shown in FIG. 1, the zoom lens of the present embodiment changes the refractive power of the first and second refractive power variable elements 101 and 105 without moving the positions of various lenses in the optical axis direction. This is a non-moving zoom lens capable of changing the focal length. Hereinafter, the refractive power (optical power) is used as a characteristic value of the lens corresponding to the reciprocal of the focal length.

  FIG. 2 is a schematic cross-sectional view showing the configuration of the first and second refractive power variable elements 101 and 105. The refractive power variable element 101 (105) employed in the zoom lens 100 of the present embodiment uses three types of liquids, and controls two interfaces formed by the three types of liquids by an electrowetting method. This is a layer type variable refractive power element. Hereinafter, the refractive power variable element that can change the refractive power by changing the shape of the interface of the liquid in this way is simply referred to as “liquid lens”. The liquid lens 101 (105) has a substantially cylindrical casing 200, and the first liquid 201, the second liquid 202, and the third liquid 203 are arranged inside the casing 200 in order from the light incident side. Three types of liquids are arranged in the optical axis direction. These three types of liquids are not mixed with each other and have different refractions at two interfaces formed by the first liquid 201 and the second liquid 202 and the second liquid 202 and the third liquid 203. Adopt material with rate. For example, water or an electrolytic aqueous solution is used as the first liquid 201 and the third liquid 203, and oil or the like is used as the second liquid 202. Hereinafter, an interface formed by the first liquid 201 and the second liquid 202 is referred to as a first interface 204, while an interface formed by the second liquid 202 and the third liquid 203 is referred to as a second interface 205. To do. Furthermore, the liquid lens 101 includes two electrodes 206 and 207, an electrode separation unit 208, and cover glasses 209 and 210. The electrodes 206 and 207 are electrodes for independently controlling the first interface 204 and the second interface 205 based on voltage supply from the outside. Each of the electrodes 206 and 207 has a shape in which a flat plate formed of two layers of a metal electrode layer and an insulating layer is an annular shape. As shown in FIG. 2, the electrodes 206 and 207 change the surface shape of each interface by controlling the contact angle between each interface and the electrode according to the applied voltage, thereby changing the overall refractive power of the liquid lens 101. Let The electrode separation unit 208 is disposed at a position where the electrode 206 and the electrode 207 face each other, and is configured by an insulating member that enables voltage control of each of the electrodes 206 and 207 independently. One of the cover glasses 209 and 210 is disposed on the light incident side of the liquid lens 101 and the other is disposed on the light emitting side, and is a glass plate that seals the liquids 201 to 203 in the liquid lens 101.

  Next, the operation of chromatic aberration correction by the zoom lens 100 will be described in comparison with a conventional zoom lens. FIG. 3 is a conceptual diagram for explaining the effect of chromatic aberration correction in the zoom lens. In particular, FIG. 3A shows components of a conventional optical system 900 having first and second refractive power variable surfaces (refractive surfaces) 301 and 302 and a stop 303 with respect to the imaging surface 304. , Optical paths of the three primary colors (R, G, B) of light are shown. In the zoom lens having the optical system 900, a control unit (not shown) changes the refractive powers φ1 and φ2 of the first and second refracting surfaces 301 and 302, thereby changing the focal length without moving the positions of the various lenses. To change. Specifically, as shown in FIG. 3A, the control unit changes the first refractive surface 301 located on the object side of the stop 303 from a negative refractive power to a positive refractive power. At the same time, the control unit changes the refractive power of the second refracting surface 302 located on the image plane side with respect to the stop 303 in the direction opposite to that of the first refracting surface 301. As a result, the optical system 900 is a negative-positive retrofocus type at the wide-angle end, and a positive-negative telephoto type at the telephoto end, so that the variable range of the focal length can be increased. At this time, the equation indicating the lateral chromatic aberration (LAT) at the wide-angle end is expressed by (Equation 1).

  Here, h is the peripheral ray height of the on-axis light beam on a certain refracting surface, h_bar is the ray height of the most off-axis principal ray on a certain refracting surface, φ is the refractive power of a certain refracting surface, and ν is The Abbe number of a certain refracting surface.

  Further, when the refracting surfaces 301 and 302 are variable surfaces (interfaces) of the liquid lens as in this embodiment, φ and ν are expressed by (Equation 2) and (Equation 3), respectively.

Here, n _d1 , n _F1 , and n _C1 indicate the refractive indices of the d-line, F-line, and C-line of one liquid in the liquid lens, and n _d2 , n _F2 , and n _C2 represent the one liquid. Refractive indexes of the d-line, F-line, and C-line of the other adjacent liquid are shown. R is the radius of curvature of the interface formed by the one liquid and the other liquid.

  Generally, in a normal liquid, the higher the refractive index, the larger the dispersion (difference in refractive index), and the lower the refractive index, the smaller the dispersion. Based on this, looking at (Equation 1), the lateral chromatic aberration appears in the same direction in the two liquid lenses for both retrofocus and telephoto. That is, with a normal zoom lens, chromatic aberration correction is performed for each zoom group to suppress fluctuations in lateral chromatic aberration. However, when the refractive power itself changes, it is difficult to correct the lateral chromatic aberration that changes for each zoom position even if a lens having a fixed refractive power is combined. Therefore, in the present embodiment, one third refracting surface 305 is newly added as shown in FIG.

  The third refracting surface 305 is a surface that generates lateral chromatic aberration opposite to that of the first and second refracting surfaces 301 and 302. At this time, the third refracting surface 305 is disposed on the image plane side of the stop 303. However, the third refracting surface needs to correct chromatic aberration up to the amount of the first refracting surface 301 with respect to the second refracting surface 302 on the image surface side of the stop 303 as well. In other words, the equation of chromatic aberration of magnification in the present embodiment is expressed by (Expression 4) when (Expression 1) is used.

  Here, the first to third terms on the left side of (Expression 4) indicate the occurrence of lateral chromatic aberration due to the first refracting surface 301, the second refracting surface 302, and the third refracting surface 305, respectively. In this case, the amount of chromatic aberration generated by combining the chromatic aberration of magnification generated on each of the three refracting surfaces is zero, and the first and second terms corresponding to the first refracting surface 301 and the second refracting surface 302 are: Since they have the same sign, the third term corresponding to the third refracting surface 305 has a different sign. Therefore, (Equation 4) is expressed by (Equation 5).

  Also, the condition that the absolute value of the amount of chromatic aberration generated on each refracting surface is zero is generally expressed by (Equation 6) when expressed by the relationship between the second refracting surface 302 and the third refracting surface 305. .

Here, (Equation 6) indicates that the lateral chromatic aberration at the wide-angle end of the second refractive surface 302 is LAT ₁ , while the lateral chromatic aberration at the wide-angle end of the third refractive surface 305 is LAT ₂ .
│LAT ₁ │ <│LAT ₂ │
It is represented by That is, the absolute value of the correction amount of the third refracting surface 305 needs to be larger than the amount of chromatic aberration generated by the second refracting surface 302. In (Expression 6), the third refracting surface 305 used for chromatic aberration correction is represented by one surface. For example, chromatic aberration correction is performed on a plurality of surfaces (refractive surfaces), and the total value is the second refracting surface. You may adjust so that it may become larger than the absolute value of 302.

In the present embodiment, the first refractive surface (first refractive power variable surface) 301 corresponds to the refractive surface 101b on the image plane side of the two refractive surfaces 101a and 101b in the three-layer first liquid lens 101. To do. On the other hand, the third refractive surface (third refractive power variable surface) 305 is enclosed in the same package as the second refractive surface (second refractive power variable surface) 302, that is, as the second liquid lens 105. Provided in one component. Specifically, in the second liquid lens 105 of the three-layer type, the object-side refractive surface 105a (the first interface 204 in FIG. 2) becomes the third refractive surface 305, while the image-side refractive surface 105b (FIG. The second second interface 205) becomes the second refractive surface 302. Thereby, the entire zoom lens 100 can be reduced in size. Note that the arrangement method of the third refracting surface 305 used for correcting the lateral chromatic aberration is not limited to this, and a separate solid lens may be arranged between the second and third refracting surfaces 302 and 305, or The liquid lenses may be arranged side by side. For example, when the third refracting surface 305 is disposed on the object side of the stop 303 (103), the lateral chromatic aberration at the wide-angle end of the liquid lens having the third refracting surface 305 is expressed on the left side (= | LAT ₁ |).

  Further, in the present embodiment, as shown in FIG. 1, the first solid lens 102 is disposed between the first liquid lens 101 and the diaphragm 103. Thereby, generation | occurrence | production of a coma aberration can be reduced. Further, as shown in FIG. 1, a positive second solid lens 104 is disposed between the diaphragm 103 and the second liquid lens 105. Thereby, in addition to downsizing of the entire zoom lens 100, occurrence of curvature of field can be reduced.

Next, the effects of the present embodiment will be described by applying the above-described conditions to the zoom lens 100 and substituting specific numerical values. (Table 1) is a table showing various numerical values in the surface numbers 601 to 620 given to the surfaces of the respective components of the zoom lens 100 shown in FIG. Here, in FIG. 4, a three-dimensional coordinate axis (Z axis, Y axis, X axis) is taken with the position of the light source (subject) as the reference of the absolute coordinate system. At this time, the Z-axis is an axis passing from the center of the 0th surface through the center of the first surface of the first liquid lens 101 (the origin of absolute coordinates) and positive in this direction. The Y-axis is an axis that passes through the center of the first surface and forms 90 degrees counterclockwise with respect to the Z-axis, and the X-axis is an axis that passes through the origin and is perpendicular to the Z-axis and the Y-axis. is there. In Table 1, for each surface number (No.), the lens type (Type), the radius of curvature (R), the thickness between the lens surfaces (D), and the refractive index of the d-line (N _d ) And Abbe number (ν _d ). Further, the first to third solid lenses 102, 104, and 106 use optical elements having rotationally symmetric aspheric surfaces, and the surface shape is expressed by (Expression 7).

  Here, k is a conic coefficient, and c is a curvature (the reciprocal of the radius of curvature R). The values of the coefficients k and A to D applied to (Equation 7) are shown in (Table 2). In Table 1, if the surface shape is a spherical surface, it is blank, and if it is a rotationally symmetric aspherical surface, it is described as AL. Similarly, for the surfaces corresponding to the liquid lenses 101 and 105, the variable value is described as Variable, and the values corresponding to the zoom positions (Position 1 and Position 2) are shown in (Table 3). Further, OBJ indicates that there is an object at infinity, and INF and STO indicate infinity and a diaphragm surface, respectively. Further, since the coordinates are inverted after the reflecting surface, the curvature radius R and the signs of the coefficients A to D are all inverted. Furthermore, (Table 4) is a table showing various values at each interface (refractive surface) in the first and second liquid lenses 101 and 105. In Table 4, in particular, Sur. Indicates the type of action of each interface, and the surface for correcting the lateral chromatic aberration is Cor. On the other hand, the surface having the refractive power necessary for zooming has Pow. Is written.

Here, as a condition of the present embodiment, the angle of view is a double zoom of 34.35 to 63.44 degrees in all angles, and FNo. Is 2.8 to 3.5. In particular, in Position 1, f = 5.78, FNo. Is 2.8, whereas in Position 2, f = 11.55, FNo. Is 3.5. In this case, the chromatic aberration of magnification at the second refracting surface 302 and the third refracting surface 305 are LAT ₁ (surface 615) = 0.0129 and LAT ₂ (surface 614) = 0.0258, respectively. The condition of 6) is satisfied.

  For reference, FIG. 5 shows a longitudinal aberration diagram (spherical aberration, image aberration, distortion) according to the present embodiment. 5A is a longitudinal aberration diagram at the wide angle end, and FIG. 5B is a longitudinal aberration diagram at the telephoto end. In FIG. 5, the vertical axis represents the height of the light beam incident on the zoom lens 100, and the horizontal axis represents the position where the light beam intersects the optical axis. In addition, FIG. 6 is a lateral aberration diagram according to the present embodiment. In particular, FIG. 6A is a lateral aberration diagram at the wide-angle end, and FIG. 6B is a lateral aberration diagram at the telephoto end. is there. In FIG. 6, the vertical axis represents the aberration amount, and the horizontal axis represents the entrance pupil coordinates. In each figure, light rays having wavelengths of C line (656.3 nm), D line (589.2 nm), and F line (486.1 nm) are described.

  As described above, the zoom lens 100 according to the present embodiment uses two three-layer liquid lenses. At this time, the interface of the first liquid lens 101 disposed on the object side of the diaphragm 103 is defined as the first refractive surface 301, and the interface of the image plane side of the second liquid lens 105 disposed on the image surface side of the diaphragm 103 is defined as the first refractive surface 301. The second refraction surface 302, on the other hand, the object-side interface is a third refraction surface 305. In the zoom lens 100, the second refracting surface 302 and the third refracting surface 305 are adjusted so that the relationship of the chromatic aberration of magnification on each refracting surface satisfies the condition of (Equation 6). It is possible to reduce the occurrence of lateral chromatic aberration. Furthermore, with this configuration, the entire zoom lens 100 can be reduced in size.

(Second Embodiment)
Next, a zoom lens according to a second embodiment of the present invention will be described. The zoom lens according to the present embodiment uses three liquid lenses while the zoom lens 100 according to the first embodiment uses two liquid lenses. FIG. 7 is a lens cross-sectional view of the zoom lens according to the present embodiment. The zoom lens 300 includes a first liquid lens 301, a first solid lens 302, a diaphragm 303, a second liquid lens 304, a second solid lens 305, in order from the object side toward the image plane 308. A third liquid lens 306 and a third solid lens 307 are provided. In FIG. 7, in particular, FIG. 7A shows a lens cross-sectional view of the zoom lens 300 at the wide-angle end (Wide). FIG. 7B is a lens cross-sectional view of the zoom lens 300 at the intermediate zoom position (Middle). FIG. 7C is a lens cross-sectional view of the zoom lens 300 at the telephoto end (Tele). Here, since the configuration of the first and third liquid lenses 301 and 306 is substantially the same as the configuration of the three-layer liquid lens according to the first embodiment, the description thereof is omitted. In the zoom lens 300, the first liquid lens 301 and the third liquid lens 306 mainly have an action of changing refractive power. In particular, the first liquid lens 301 changes the focal length greatly by changing the refractive power from negative to positive while the third liquid lens 306 changes the refractive power from positive to negative. In this case, the refracting surface that functions as a variable surface of the focal length forms the second interface 301b of the first and second interfaces 301a and 301b forming the first liquid lens 301 and the third liquid lens 306. This is the second interface 306b of the first and second interfaces 306a and 306b. On the other hand, as in the first embodiment, the refractive surface that functions as a correction surface for the lateral chromatic aberration is the first interface 306 a of the third liquid lens 306.

  In the present embodiment, the refractive surface that functions as a correction surface for the lateral chromatic aberration is the first interface 306a of the third liquid lens 306, but the correction surface for the lateral chromatic aberration is not limited to this. The lateral chromatic aberration is proportional to the product of the peripheral ray height h and the principal ray height h_bar on each surface, as shown in (Equation 1). Therefore, the chromatic aberration of magnification can be further reduced if the optical surface having the maximum h × (h_bar) among the refracting surfaces is used as the correction surface of the chromatic aberration of magnification. On the other hand, when the correction surface for the magnification chromatic aberration is a surface having the maximum principal ray height h_bar, the magnification chromatic aberration can be corrected independently of the longitudinal chromatic aberration. In the present embodiment, the surface having the maximum h × (h_bar) (the first interface 306a of the third liquid lens 306) is used as the correction surface for the lateral chromatic aberration, so that the lateral chromatic aberration is effectively reduced.

  In the present embodiment, the correction surface for the lateral chromatic aberration is configured by one surface on the image plane side with respect to the stop 303. For example, a plurality of surfaces are similarly formed on the image plane side of the stop 303. It is good also as a structure to arrange. In this case, the chromatic aberration of magnification LAT of the correction surface may be overcorrected if the total correction amount of the refracting surface is over, assuming that there are N refracting surfaces for correction, as shown in (Equation 8).

  Further, in the present embodiment, unlike the first embodiment, the axial chromatic aberration is corrected by newly adding a second liquid lens 304 composed of a two-layer liquid lens. The equation for correcting axial chromatic aberration is expressed by (Equation 9).

  Here, when only the first liquid lens 301 and the second liquid lens 306 are considered, each refractive power φ is negative-positive at the wide-angle end, and positive-negative at the telephoto end. The peripheral ray height h is always positive because it is a system that does not perform intermediate imaging. Therefore, the axial chromatic aberration in the zoom lens in this case is always in the correction direction. However, in practice, since there is an influence of other aberrations, particularly at the telephoto end, it is difficult to always maintain the state in which the axial chromatic aberration is corrected at any zoom position. Therefore, in the present embodiment, the axial chromatic aberration can be corrected for each zoom position by disposing the second liquid lens 304 next to the stop 303 (object side or image plane side). At this time, the second liquid lens 304 is arranged next to the stop 303 because the principal ray height h_bar in (Equation 1) is close to zero, so that axial chromatic aberration is corrected independently of lateral chromatic aberration. Because it can. Here, next to the diaphragm 303, as shown in FIG. 7C, the distance at the telephoto end from the diaphragm 303 to the interface (fourth refractive power variable surface) 304a in the second liquid lens 304 is S. When the total length of the zoom lens 300 is L, S / L <0.2 is satisfied. In this case, if S / L exceeds 0.2, it is difficult to independently correct longitudinal chromatic aberration, and chromatic aberration may increase.

Next, the effects of this embodiment will be described by applying the above-described conditions to the zoom lens 300 and substituting specific numerical values. (Table 5) is a table showing various numerical values in the surface numbers 901 to 924 given to the surfaces of the respective components of the zoom lens 300 shown in FIG. Each coefficient applied to the above (Formula 7) is shown in (Table 6). Further, in (Table 5), values corresponding to the respective zoom positions (Position 1, Position 2, and Position 3) are shown in (Table 7). These (Table 5) to (Table 7) correspond to (Table 1) to (Table 3) according to the first embodiment, respectively. Here, as a condition of the present embodiment, the angle of view is a 3 × zoom of 23.29 to 63.44 degrees in all angles. Is 2.8 to 5.0. In particular, in Position 1, f = 5.78, FNo. Is 2.8, and in Position 2, f = 9.08, FNo. Is 3.5, and in Position 3, f = 17.33, FNo. Is 5.0. Then, the chromatic aberration of magnification at the first interface 306a and the second interface 306b in the third liquid lens 306 are LAT ₁ (surface 919) = 0.0003 and LAT ₂ (surface 918) = 0.0097 ((h Xh_bar) is the maximum), and the condition of (Equation 6) is satisfied. In this case, since L = 29.642 and S = 0.02541, S / L = 0.025, which satisfies the condition of S / L <0.2. For reference, FIGS. 9 and 10 show longitudinal aberration diagrams (spherical aberration, image surface aberration, distortion) and lateral aberration diagrams at the wide-angle end and the telephoto end according to this embodiment. FIGS. 9 and 10 correspond to FIGS. 5 and 6 according to the first embodiment. In particular, in both figures, (a) is a wide angle end (Wide), and (b) is an intermediate zoom. The position (Middle) and (c) correspond to the telephoto end (Tele). Thereby, according to this embodiment, in addition to the effect similar to 1st Embodiment, the axial chromatic aberration for every zoom position can be reduced.

(Third embodiment)
Next, a zoom lens according to a third embodiment of the present invention will be described. The zoom lens according to the present embodiment uses four liquid lenses, and a right-angle prism is disposed in the optical path, thereby reducing the thickness. FIG. 11 is a lens cross-sectional view of the zoom lens according to the present embodiment. The zoom lens 400 includes a first liquid lens 401, a right-angle prism (glass prism) 402, a second liquid lens 403, a first solid lens 404, and an aperture 405 in order from the object side toward the image plane 410. And a third liquid lens 406. Subsequently, the zoom lens 300 includes a second solid lens 407, a fourth liquid lens 408, and a third solid lens 409. In FIG. 11, in particular, FIG. 11A shows a lens cross-sectional view of the zoom lens 400 at the wide-angle end (Wide). FIG. 11B is a lens cross-sectional view of the zoom lens 400 at an intermediate zoom position (Middle). FIG. 11C is a lens cross-sectional view of the zoom lens 400 at the telephoto end (Tele). In the zoom lens 400, the first, second, and third liquid lenses 401, 403, and 406 are two-layer liquid lenses using two types of liquids. In this case, the first liquid lens 401 and the second liquid lens 403 are arranged with the right-angle prism 402 between them, and as a result, the three-layer liquid lens of the zoom lens 300 according to the second embodiment is changed to 2. The configuration is the same as that of two two-layer liquid lenses. The configuration of the fourth liquid lens 408 is substantially the same as the configuration of the three-layer liquid lens according to the first embodiment. In the zoom lens 400, the first liquid lens 401 and the second liquid lens 403 mainly have an action of changing refractive power. In particular, the first liquid lens 401 changes the focal length greatly by changing the refractive power from negative to positive, while the second liquid lens 403 changes the refractive power from positive to negative. On the other hand, as in the first embodiment, the refractive surface that functions as a correction surface for the lateral chromatic aberration is the first interface 408 a of the fourth liquid lens 408. On the other hand, the second interface 408b of the fourth liquid lens 408 has a function of changing the refractive power so as not to move the position of the imaging plane 410 when the focal length of the zoom lens 400 changes. Similarly to the second liquid lens 304 in the second embodiment, the third liquid lens 406 is disposed next to the diaphragm 405 and has an action of reducing axial chromatic aberration caused by a change in another liquid lens.

Next, the effects of this embodiment will be described by applying the above-described conditions to the zoom lens 400 and substituting specific numerical values. (Table 9) is a table showing various numerical values in the surface numbers 1201 to 1228 attached to the surfaces of the components of the zoom lens 400 shown in FIG. Each coefficient applied to the above (Formula 7) is shown in (Table 10). Further, in (Table 9), values corresponding to the respective zoom positions (Position 1, Position 2, and Position 3) are shown in (Table 11). These (Table 9) to (Table 11) correspond to (Table 1) to (Table 3) according to the first embodiment, respectively. Here, as a condition of the present embodiment, the angle of view is a 3 × zoom of 23.29 to 63.44 degrees in all angles. Is 2.8 to 5.0. In particular, in Position 1, f = 5.78, FNo. Is 2.8, and in Position 2, f = 9.08, FNo. Is 3.5, and in Position 3, f = 17.33, FNo. Is 5.0. Then, the chromatic aberration of magnification at the first interface 408a and the second interface 408b in the fourth liquid lens 408 are LAT ₁ (surface 1223) = 0.0035 and LAT ₂ (surface 1222) = − 0.0126 (( h × h_bar) is maximum), and the condition of (Expression 6) is satisfied. In this case, since L = 40.0 (A + B shown in FIG. 11 (c)) and S = 0.0366, S / L = 0.0009, and the condition of S / L <0.2 is satisfied. Fulfill. For reference, FIGS. 13 and 14 show longitudinal aberration diagrams (spherical aberration, field aberration, distortion) and lateral aberration diagrams at the wide-angle end and the telephoto end according to this embodiment. FIGS. 13 and 14 correspond to FIGS. 9 and 10 according to the second embodiment. Thereby, according to this embodiment, in addition to the effect similar to 2nd Embodiment, the shape of the whole zoom lens can be made thin.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  For example, in the above-described embodiment, the refracting surface and the chromatic aberration of magnification correction surface are configured by one three-layer liquid lens, but the present invention is not limited to this. For example, a plurality of two-layer liquid lenses may be combined, or a liquid lens using a liquid crystal element or the like may be used for zooming, and a liquid interface may be added as a magnification chromatic aberration correction surface.

  In the above embodiment, the chromatic aberration correction surface is arranged between the stop and the refractive surface on the image plane side, but the present invention is not limited to this. In this case, it may be arranged at any position as long as the chromatic aberration of magnification can be corrected. However, it is desirable that the position where the lateral chromatic aberration can be efficiently corrected, that is, either the position where h × (h_bar) is maximum or the position where the principal ray height (h_bar) is maximum.

DESCRIPTION OF SYMBOLS 100 Zoom lens 101 1st liquid lens 101b 1st refractive surface 103 Diaphragm 105 2nd liquid lens 105a 3rd refractive surface 105b 2nd refractive surface

Claims (8)

A first refracting power variable surface disposed on the object side of the stop, and a second refracting power disposed on the image surface side of the stop that causes chromatic aberration of magnification having the same sign as the first refracting power variable surface. A zoom lens including a variable surface, and the first and second refractive power variable surfaces and a third refractive power variable surface that causes lateral chromatic aberration with a different sign,
When the third refractive power variable surface is disposed on the object side of the diaphragm, the lateral chromatic aberration at the wide-angle end of the first refractive power variable surface is LAT ₁ or the third refractive power variable surface. Is arranged at the image plane side of the stop, the lateral chromatic aberration at the wide-angle end of the second refractive power variable surface is LAT _1, and the lateral chromatic aberration at the wide-angle end of the third refractive power variable surface is LAT. ₂
│LAT ₁ │ <│LAT ₂ │
A zoom lens characterized by satisfying the following conditions:   The third refractive power variable surface is disposed on an optical surface where the product of the ray height of the most off-axis principal ray and the marginal ray height of the on-axis light beam is maximized at the wide angle end. The zoom lens according to claim 1.   2. The zoom lens according to claim 1, wherein the third refractive power variable surface is disposed on an optical surface where the ray height of the most off-axis chief ray is maximum at the wide angle end.   The third refractive power variable surface is one surface constituting a three-layer type liquid lens enclosed in the same package as the first refractive power variable surface or the second refractive power variable surface. The zoom lens according to claim 1, wherein the zoom lens is characterized in that:   5. The zoom lens according to claim 1, further comprising a fourth refractive power variable surface adjacent to the object side or the image surface side of the stop. When the distance between the fourth refractive power variable surface and the diaphragm is S, and the total length of the zoom lens is L,
S / L <0.2
The zoom lens according to claim 5, wherein the following condition is satisfied.   The zoom lens according to claim 1, wherein a solid lens is disposed between the diaphragm and the first refractive power variable surface.   The zoom lens according to claim 1, wherein a solid lens is disposed between the diaphragm and the second refractive power variable surface.

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