JP5327593B2 - Projection lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection lens in which various aberrations are satisfactorily corrected despite a small, short optical system. <P>SOLUTION: The projection lens has, in order from the projection side, a first lens component L1 of negative refractive power, which has a meniscus shape, and a second lens component L2 of positive refractive power, which has a biconvex shape. All the lens faces of the first lens and second lens components L1 and L2 are aspherical. When the curvature radii of spherical lenses obtained by approximating the lens face to a spherical face by a method of least squares relative to the maximum effective diameter of the actual shape of the projection side aspherical face of the first lens component L1 and a half of the maximum effective diameter are represented by Rf11 and Rh11 respectively, and similarly the curvature radii of a spherical face obtained by approximating the lens face to a spherical face relative to the maximum effective diameter of the actual shape of the object side aspherical face and a half of it are represented by Rf12 and Rh12 respectively. The conditions expressed by expressions below are satisfied: 0.13&le;(Rf11-Rh11)/Rf11&le;1.00 and 0.13&le;(Rf12-Rh12)/Rf12&le;1.00. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention particularly relates to a projection lens suitable for a projector for projecting an image displayed on an image display element or the like onto a screen.

Conventionally, projector apparatuses that use an image display element such as a liquid crystal element and project an image based on the display element onto a screen are often used, and a projection lens for a projector that can display a high-definition image has been used. Various proposals have been made (for example, see Patent Document 1).
JP 2003-98431 A

  In recent years, there has been a demand for downsizing and compactness of the projector device. To that end, it is necessary to make the projection lens used in the projector device small. In order to realize such a small projector, there is a demand for a projection lens that is configured with a limited number of constituents (two necessary minimums) while maintaining performance by correcting various aberrations. .

  The present invention has been made in view of such problems, and an object thereof is to provide a projection lens in which various aberrations are favorably corrected while the optical system is small and short.

In order to achieve such an object, the projection lens of the present invention includes, in order from the projection side, a first lens component having a meniscus negative refractive power and a second lens component having a biconvex positive refractive power. Are substantially composed of two lenses, and in order from the projection side to the object side, the lens surface on the projection side of the first lens component, the lens surface on the object side of the first lens component, and the second lens The lens surface on the projection side of the component and the lens surface on the object side of the second lens component are all aspherical surfaces, and with respect to the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the first lens component, The spherical curvature when approximated to the spherical surface by the least square method is Rf11, and the spherical surface is approximated to the spherical surface by the least square method for half the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the first lens component. The curvature of the spherical surface is Rh11 , The curvature of the spherical surface of the first lens component on the object side of the first lens component is Rf12 with respect to the maximum effective diameter of the actual shape of the aspheric surface on the object side of the first lens component. When the curvature of the spherical surface when Rh12 is approximated to the spherical surface by the least square method with respect to half of the maximum effective diameter of the actual shape of the aspherical surface is Rh12, the following expression 0.13 ≦ (Rf11−Rh11) / Rf11 ≦ 1 0.00 and 0.13 ≦ (Rf12−Rh12) /Rf12≦1.00 are satisfied.

  Note that the curvature of the spherical surface when approximated to a spherical surface by the least square method is Rf21 with respect to the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the second lens component, and the projection side of the second lens component For the half of the maximum effective diameter of the actual shape of the aspherical surface, the curvature of the spherical surface when approximated to the spherical surface by the least square method is Rh21, and the actual shape of the aspherical surface on the object side of the second lens component is For the maximum effective diameter, the curvature of the spherical surface when approximated to the spherical surface by the least square method is Rf22, and the minimum effective diameter is half the maximum effective diameter of the actual shape of the aspherical surface on the object side of the second lens component. When the curvature of the spherical surface approximated to the spherical surface by the square method is Rh22, the following conditions are satisfied: 0 ≦ (Rf21−Rh21) /Rf21≦0.13 and 0 ≦ (Rf22−Rh22) /Rf22≦0.19 It is preferable to satisfy.

  Further, it is preferable that the first lens component is a lens component made of at least one plastic lens.

  Further, when the Abbe number of the first lens component with respect to the d-line is νd1, it is preferable that the condition of the following expression 27 ≦ νd1 ≦ 35 is satisfied.

  Further, when the refractive index of the first lens component with respect to the d-line is nd1, it is preferable that the condition of the following formula 1.50 ≦ nd1 ≦ 1.65 is satisfied.

  Further, it is preferable that the second lens component is a lens component made of at least one plastic lens.

  Further, when the Abbe number of the second lens component with respect to the d-line is νd2, it is preferable that the condition of the following expression 53 ≦ νd2 ≦ 61 is satisfied.

  In addition, when the refractive index of the second lens component with respect to the d-line is nd2, it is preferable that the condition of the following formula 1.45 ≦ nd2 ≦ 1.60 is satisfied.

  It is preferable that an aperture stop is provided on the projection side with respect to the first lens component.

  According to the present invention, it is possible to provide a projection lens in which various aberrations are favorably corrected while the optical system is small and short, and high optical performance can be obtained over the entire projection surface.

  Hereinafter, preferred embodiments will be described with reference to the drawings. As shown in FIG. 1, the projection lens according to this embodiment includes, in order from the projection side, a first lens component L1 having a meniscus negative refractive power and a second lens having a biconvex positive refractive power. Component L2, and in order from the projection side to the object side, the projection side lens surface of the first lens component L1, the object side lens surface of the first lens component L1, and the projection side of the second lens component L2 The lens surface and the lens surface on the object side of the second lens component L2 are all aspherical.

  As described above, since the projection lens according to the present embodiment is substantially composed of two lenses (lens components), it has a compact and compact configuration in which the entire length of the optical system is short. Further, by configuring the first lens component L1 having negative refractive power and the second lens component L2 having positive refractive power in combination, axial chromatic aberration can be corrected well.

  In the present embodiment, based on the above configuration, the curvature of the spherical surface is approximated to the spherical surface by the least square method with respect to the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the first lens component L1. Rf11, and the curvature of the spherical surface when Rh11 is approximated to the spherical surface by the least square method with respect to half the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the first lens component L1, is Rh11. The spherical surface ratio when approximated to a spherical surface by the least square method with respect to the maximum effective diameter of the actual shape of the aspherical surface on the object side is Rf12, and the actual shape of the aspherical surface on the object side of the first lens component L1. When the curvature of the spherical surface when Rh12 is approximated to the spherical surface by the least square method with respect to half of the maximum effective diameter, the conditions of the following expressions (1) and (2) are satisfied.

0.13 ≦ (Rf11−Rh11) /Rf11≦1.00 (1)
0.13 ≦ (Rf12−Rh12) /Rf12≦1.00 (2)

  The conditional expression (1) indicates an appropriate range of the difference in curvature (= Rf11−Rh11) with respect to the curvature Rf11 on the projection-side lens surface of the first lens component L1. The conditional expression (2) represents an appropriate range of the difference in curvature (= Rf12−Rh12) with respect to the curvature Rf12 on the object-side lens surface of the first lens component. By satisfying these conditional expressions (1) and (2), it is possible to satisfactorily correct spherical aberration, curvature of field, and distortion (distortion), and improve imaging performance around the projection surface. When conditional expression (1) cannot be satisfied, it becomes difficult to correct spherical aberration, which is not preferable. On the other hand, when the conditional expression (2) cannot be satisfied, the refractive power balance between the lens surface on the object side of the first lens component L1 and the lens surface on the projection side of the second lens component is lost, and field curvature and distortion are lost. Is difficult to correct, and the imaging performance around the projection surface is deteriorated.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 0.80. In order to further secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 0.50. In order to further secure the effect of the present embodiment, it is preferable to set the upper limit value of conditional expression (1) to 0.30. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 0.15.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.80. In order to further secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.50. In order to further secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 0.30. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 0.15.

  In the present embodiment, the curvature of the spherical surface when the spherical surface is approximated to the spherical surface by the least square method with respect to the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the second lens component L2 is Rf21. The curvature of the spherical surface when Rh21 is approximated to the spherical surface by the least square method for half of the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the component L2 is Rh21, and the aspherical surface on the object side of the second lens component L2 When the spherical surface is approximated to a spherical surface by the least-squares method with respect to the maximum effective diameter of the actual shape, the spherical surface ratio is Rf22, and is half the maximum effective diameter of the actual shape of the aspherical surface on the object side of the second lens component L2. On the other hand, when the curvature of the spherical surface approximated to the spherical surface by the least square method is Rh22, it is preferable that the conditions of the following expressions (3) and (4) are satisfied.

0 ≦ (Rf21−Rh21) /Rf21≦0.13 (3)
0 ≦ (Rf22−Rh22) /Rf22≦0.19 (4)

  Conditional expression (3) indicates an appropriate range of the difference in curvature (= Rf21−Rh21) with respect to the curvature Rf21 on the projection-side lens surface of the second lens component L2. The conditional expression (4) represents an appropriate range of the difference in curvature (= Rf22−Rh22) with respect to the curvature Rf22 on the object side lens surface of the second lens component L2. When the conditional expression (3) cannot be satisfied, the balance of refractive power between the object-side lens surface of the first lens component L1 and the projection-side lens surface of the second lens component L2 is lost, and field curvature and distortion are reduced. It becomes difficult to correct, and the imaging performance around the projection surface is deteriorated. On the other hand, when the conditional expression (4) cannot be satisfied, it is difficult to correct astigmatism, which is not preferable.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 0.10. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.015.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 0.16. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 0.015.

  In the present embodiment, the first lens component L1 is preferably composed of at least one plastic lens. Here, since the plastic lens is manufactured by molding such as injection molding, even if the surface shape is an aspherical surface, it is not difficult to manufacture compared to the spherical surface, and the cost is hardly increased. For this reason, by plasticizing the first lens component L1 having aspheric surfaces on both sides, the manufacturing cost can be reduced and the weight of the entire lens system can be reduced as compared with the case where a glass mold aspheric lens is used. .

  In the present embodiment, it is preferable that the condition of the following expression (5) is satisfied when the Abbe number of the first lens component L1 with respect to the d-line is νd1.

  27 ≦ νd1 ≦ 35 (5)

  Conditional expression (5) shows an appropriate range of the Abbe number νd1 of the first lens component L1. This condition is effective for sufficient correction of chromatic aberration. If this condition cannot be satisfied, it is difficult to correct both axial chromatic aberration and lateral chromatic aberration in the first lens component L1, which is not preferable.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (5) to 33. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (5) to 29.

  In the present embodiment, it is preferable that the condition of the following expression (6) is satisfied when the refractive index of the first lens component L1 with respect to the d-line is nd1.

  1.50 ≦ nd1 ≦ 1.65 (6)

  Conditional expression (6) shows an appropriate range of the refractive index nd1 of the first lens component L1. If this conditional expression cannot be satisfied, it is not preferable because a sufficient enlargement ratio and angle of view cannot be secured, and correction of field curvature becomes difficult.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (6) to 1.60. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (6) to 1.55.

  In the present embodiment, it is preferable that the second lens component L2 is composed of at least one plastic lens. Thus, by plasticizing the second lens component L2 having aspheric surfaces on both sides, the manufacturing cost can be reduced and the weight of the entire lens system can be reduced compared to the case of using a glass molded aspheric lens. it can.

  In the present embodiment, it is preferable that the condition of the following expression (7) is satisfied when the Abbe number of the second lens component L2 with respect to the d-line is νd2.

  53 ≦ νd2 ≦ 61 (7)

  Conditional expression (7) shows an appropriate range of the Abbe number νd2 of the second lens component L2. This condition is effective for sufficient correction of chromatic aberration. If this condition cannot be satisfied, it is difficult to correct both longitudinal chromatic aberration and lateral chromatic aberration in the second lens component L2, which is not preferable.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (7) to 59. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (7) to 55.

  In the present embodiment, it is preferable that the condition of the following formula (8) is satisfied when the refractive index of the second lens component L2 with respect to the d-line is nd2.

  1.45 ≦ nd2 ≦ 1.60 (8)

  Conditional expression (8) shows an appropriate range of the refractive index nd2 of the second lens component L2. If this conditional expression cannot be satisfied, a sufficient enlargement ratio and angle of view cannot be secured, and correction of field curvature becomes difficult, which is not preferable.

  In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (8) to 1.55. In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (8) to 1.50.

  In the present embodiment, it is preferable to provide the aperture stop S on the projection side with respect to the first lens component L1. This configuration is preferable because extra light can be limited and coma can be reduced.

  Hereinafter, each example according to the present embodiment will be described with reference to the drawings. 1, 3, and 5 are cross-sectional views illustrating the configuration of the projection lens according to each example. As described above, the projection lenses according to the respective examples are, in order from the projection side, the first lens component L1 having a meniscus negative refractive power and the second lens having a biconvex positive refractive power. Component L2, and in order from the projection side to the object side, the projection side lens surface of the first lens component L1, the object side lens surface of the first lens component L1, and the projection side of the second lens component L2 The lens surface and the object-side lens surface of the second lens component L2 are all aspherical surfaces, and are substantially composed of two lenses (lens components).

  Tables 1 to 3 are shown below, but these are tables of specifications in the first to third examples. In [Lens data], the surface number is the order of the lens surfaces from the projection side (the 0th surface corresponds to the projection surface), r is the radius of curvature of each lens surface, and d is the next optical surface from each optical surface. Is the distance between the surfaces on the optical axis (the value described on the 0th surface corresponds to the air distance from the projection surface to the first surface), nd is the refractive index for the d-line (wavelength 587.6 nm), νd Indicates the Abbe number with respect to the d-line. When the lens surface is aspherical, an asterisk is attached to the surface number, and the paraxial radius of curvature is indicated in the column of the radius of curvature r. The curvature radius “0.000” indicates a plane or an opening. Further, the description of the refractive index “1.00000” of air is omitted.

In [Aspherical data], the shape of the aspherical surface shown in [Lens data] is shown by the following equation (a). That is, y is the height in the direction perpendicular to the optical axis, and S (y) is the distance (sag amount) along the optical axis from the tangent plane at the apex of the aspheric surface to the position on the aspheric surface at height y. When the radius of curvature (paraxial radius of curvature) of the reference spherical surface is r, the conic coefficient is K, and the n-th aspherical coefficient is An, the following equation (a) is given. In each example, the secondary aspheric coefficient A2 is 0, and the description thereof is omitted. Further, En represents × 10 ^n. For example, 1.234E-05 = 1.234 × 10 ⁻⁵ .

S (y) = (y ² / r) / {1+ (1−K · y ² / r ² ) ^1/2 }
^{+ A4 × y 4 + A6 ×} y 6 + A8 × y 8 + A10 × y 10 ... (a)

  In [various data], f is the focal length of the entire lens system, FNO is the F number, 2ω is the angle of view, f1 is the focal length of the first lens component L1, and f2 is the focal length of the second lens component L2. Indicates. In [Conditional Expression], the conditional expressions (1) to (8) and values corresponding thereto are shown.

  In the table, “mm” is generally used as the unit of focal length f, radius of curvature r, surface interval d, and other lengths. However, since the optical system can obtain the same optical performance even when proportionally enlarged or proportionally reduced, the unit is not limited to “mm”, and other appropriate units can be used.

  The description of the above table is the same in other examples, and the description thereof is omitted.

(First embodiment)
The projection lens according to the first example will be described with reference to FIGS. As shown in FIG. 1, the projection lens according to the first example includes a negative meniscus lens L1 (first lens component) arranged in order from the projection side (screen side) and having a convex surface on the projection side, and a biconvex shape. And a positive lens L2 (second lens component). Further, in order from the projection side to the object side (image display element side), the projection-side lens surface of the negative meniscus lens L1, the object-side lens surface of the negative meniscus lens L1, the projection-side lens surface of the positive lens L2, The lens surface on the object side of the positive lens L2 is all aspherical.

  Note that an aperture stop S for cutting harmful light is disposed on the projection side of the negative meniscus lens L1. Further, on the object side of the positive lens L2, a parallel flat glass GB corresponding to a color synthesis prism or the like and an image display element LCD such as a liquid crystal panel are arranged.

  Table 1 shows a table of specifications in the first embodiment. The surface numbers 1 to 7 in Table 1 correspond to the surfaces 1 to 7 shown in FIG. In the first embodiment, the lens surfaces of the second surface, the third surface, the fourth surface, and the fifth surface are all aspherical.

(Table 1)
[Lens data]
Surface number r d nd νd
0 545.000
1 0.000 16.500 (Aperture stop S)
* 2 9.610 2.700 1.58 30.3
* 3 7.040 1.300
* 4 15.120 4.500 1.53 56.0
* 5 -15.110 10.235
6 0.000 10.000 1.72 29.5
7 0.000 1.500
[Aspherical data]
2nd surface κ = -3.3773, A4 = 3.4683E-04, A6 = -1.1624E-05, A8 = 9.6377E-08, A10 = 0.0000E + 00
3rd surface κ = 0.24149, A4 = 2.1804E-05, A6 = -1.7585E-05, A8 = 1.8590E-07, A10 = 0.0000E + 00
4th surface κ = 3.5971, A4 = 1.4212E-04, A6 = -1.1640E-05, A8 = 8.2440E-08, A10 = 0.0000E + 00
5th surface κ = -12.140, A4 = -3.1722E-04, A6 = 2.2483E-06, A8 = 5.2402E-09,
A10 = 0.0000E + 00
[Various data]
f = 20.44
FNO = 2.8
2ω = 28.67
f1 = -73.67
f2 = 14.96
[Conditional expression]
Rf11 = 12.36
Rh11 = 10.11
Rf12 = 9.31
Rh12 = 7.37
Rf21 = 15.53
Rh21 = 14.59
Rf22 = -15.97
Rh22 = -15.53
Conditional expression (1) (Rf11-Rh11) /Rf11=0.18
Conditional expression (2) (Rf12-Rh12) /Rf12=0.21
Conditional expression (3) (Rf21-Rh21) /Rf21=0.06
Conditional expression (4) (Rf22-Rh22) /Rf22=0.03
Conditional expression (5) νd1 = 30.3
Conditional expression (6) nd1 = 1.58
Conditional expression (7) νd2 = 56.0
Conditional expression (8) nd2 = 1.53

  From the table of specifications shown in Table 1, it can be seen that the projection lens according to the first example satisfies all the conditional expressions (1) to (8).

  FIG. 2 is a diagram showing various aberrations (spherical aberration diagram, astigmatism diagram, distortion aberration diagram, lateral chromatic aberration diagram, and coma aberration diagram) of the first example. In each aberration diagram, FNO represents an F number, Y represents an object height (image height of an image display element), and H0 represents an image height (image height of a projection surface). D is the d-line (wavelength 587.6 nm), g is the g-line (wavelength 435.8 nm), C is the C-line (wavelength 656.3 nm), and F is the aberrations for the F-line (wavelength 486.1 nm). Indicates various aberrations with respect to the d-line. In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. The explanation of the above aberration diagrams is the same in the other examples, and the explanation is omitted.

  As is apparent from each aberration diagram, the projection lens according to the first example is composed of two lenses, and thus has a compact and compact configuration in which the overall length of the optical system is short. It can also be seen that, despite the two-lens configuration, various aberrations are well corrected and have excellent imaging performance.

(Second embodiment)
The projection lens according to Example 2 will be described with reference to FIGS. 3 and 4 and Table 2. FIG. As shown in FIG. 3, the projection lens according to the second example includes a negative meniscus lens L1 (first lens component) having a convex surface facing the projection side and a biconvex positive lens L2 arranged in order from the projection side. It is configured to have two lenses (second lens component). Further, in order from the projection side to the object side, the projection-side lens surface of the negative meniscus lens L1, the object-side lens surface of the negative meniscus lens L1, the projection-side lens surface of the positive lens L2, and the object of the positive lens L2 The lens surface on the side is all aspherical.

  Note that an aperture stop S for cutting harmful light is disposed on the projection side of the negative meniscus lens L1. Further, on the object side of the positive lens L2, a parallel flat glass GB corresponding to a color synthesis prism or the like and an image display element LCD such as a liquid crystal panel are arranged.

  Table 2 shows a table of specifications in the second embodiment. The surface numbers 1 to 7 in Table 2 correspond to the surfaces 1 to 7 shown in FIG. In the second embodiment, the lens surfaces of the second surface, the third surface, the fourth surface, and the fifth surface are all aspherical.

(Table 2)
[Lens data]
Surface number r d nd νd
0 539.200
1 0.000 10.800 (Aperture stop S)
* 2 10.650 3.000 1.58 30.3
* 3 7.000 1.000
* 4 11.810 4.500 1.53 56.0
* 5 -10.030 7.620
6 0.000 7.000 1.72 29.5
7 0.000 1.500
[Aspherical data]
Second side κ = 2.3735, A4 = -7.9646E-04, A6 = -1.8674E-06, A8 = 0.0000E + 00, A10 = 0.0000E + 00
3rd surface κ = -2.2864, A4 = 6.8843E-05, A6 = -8.7807E-06, A8 = 2.6315E-07, A10 = 0.0000E + 00
4th surface κ = 2.5372, A4 = -3.1904E-04, A6 = 6.3205E-07, A8 = -4.4071E-08, A10 = 0.0000E + 00
5th surface κ = -3.3749, A4 = -3.4719E-04, A6 = 4.5057E-06, A8 = -7.5277E-08, A10 = 0.0000E + 00
[Various data]
f = 14.98
FNO = 2.5
2ω = 20.75
f1 = -50.26
f2 = 10.97
[Conditional expression]
Rf11 = 15.47
Rh11 = 11.75
Rf12 = 9.50
Rh12 = 7.75
Rf21 = 13.11
Rh21 = 12.26
Rf22 = -10.86
Rh22 = -10.35
Conditional expression (1) (Rf11-Rh11) /Rf11=0.24
Conditional expression (2) (Rf12-Rh12) /Rf12=0.18
Conditional expression (3) (Rf21-Rh21) /Rf21=0.06
Conditional expression (4) (Rf22-Rh22) /Rf22=0.05
Conditional expression (5) νd1 = 30.3
Conditional expression (6) nd1 = 1.58
Conditional expression (7) νd2 = 56.0
Conditional expression (8) nd2 = 1.53

  From the table of specifications shown in Table 2, it can be seen that the projection lens according to Example 2 satisfies all the conditional expressions (1) to (8).

  FIG. 4 is a diagram showing various aberrations (spherical aberration diagram, astigmatism diagram, distortion aberration diagram, chromatic aberration diagram of magnification, and coma aberration diagram) of the second example. As is apparent from each aberration diagram, the projection lens according to Example 2 is composed of two lenses, and thus has a compact and compact configuration in which the overall length of the optical system is short. It can also be seen that, despite the two-lens configuration, various aberrations are well corrected and have excellent imaging performance.

(Third embodiment)
The projection lens according to the third example will be described with reference to FIGS. As shown in FIG. 5, the projection lens according to the third example includes a negative meniscus lens L1 (first lens component) having a convex surface facing the projection side and a biconvex positive lens L2 arranged in order from the projection side. It is configured to have two lenses (second lens component). Further, in order from the projection side to the object side, the projection-side lens surface of the negative meniscus lens L1, the object-side lens surface of the negative meniscus lens L1, the projection-side lens surface of the positive lens L2, and the object of the positive lens L2 The lens surface on the side is all aspherical.

  Note that an aperture stop S for cutting harmful light is disposed on the projection side of the negative meniscus lens L1. Further, on the object side of the positive lens L2, a parallel flat glass GB corresponding to a color synthesis prism or the like and an image display element LCD such as a liquid crystal panel are arranged.

  Table 3 shows a table of specifications in the third embodiment. The surface numbers 1 to 7 in Table 3 correspond to the surfaces 1 to 7 shown in FIG. In the third embodiment, the second surface, the third surface, the fourth surface, and the fifth surface are all aspherical.

(Table 3)
[Lens data]
Surface number r d nd νd
0 550.000
1 0.000 11.500 (Aperture stop S)
* 2 7.980 2.900 1.58 30.3
* 3 5.000 1.200
* 4 9.790 5.240 1.53 56.0
* 5 -14.320 9.563
6 0.000 10.800 1.80 46.6
7 0.000 1.500
[Aspherical data]
Second surface κ = -1.1062, A4 = -2.6065E-04, A6 = -1.5461E-06, A8 = 5.2356E-08, A10 = 0.0000E + 00
3rd surface κ = -0.4823, A4 = -2.6267E-04, A6 = -4.8391E-06, A8 = 9.5161E-08, A10 = 0.0000E + 00
4th surface κ = -0.7469, A4 = 2.0877E-04, A6 = -5.3155E-06, A8 = 5.2968E-08, A10 = 0.0000E + 00
5th surface κ = -15.6040, A4 = -4.4799E-04, A6 = 8.9881E-06, A8 = -5.2373E-08, A10 = 0.0000E + 00
[Various data]
f = 19.30
FNO = 2.7
2ω = 30.58
f1 = -35.76
f2 = 11.80
[Conditional expression]
Rf11 = 12.12
Rh11 = 9.02
Rf12 = 8.26
Rh12 = 6.26
Rf21 = 10.94
Rh21 = 9.96
Rf22 = -17.60
Rh22 = -15.08
Conditional expression (1) (Rf11-Rh11) /Rf11=0.26
Conditional expression (2) (Rf12-Rh12) /Rf12=0.24
Conditional expression (3) (Rf21-Rh21) /Rf21=0.09
Conditional expression (4) (Rf22-Rh22) /Rf22=0.14
Conditional expression (5) νd1 = 30.3
Conditional expression (6) nd1 = 1.58
Conditional expression (7) νd2 = 56.0
Conditional expression (8) nd2 = 1.53

  From the table of specifications shown in Table 3, it can be seen that the projection lens according to Example 3 satisfies all the conditional expressions (1) to (8).

  FIG. 6 is a diagram showing various aberrations (spherical aberration diagram, astigmatism diagram, distortion aberration diagram, chromatic aberration diagram of magnification, and coma aberration diagram) of the third example. As is apparent from each aberration diagram, the projection lens according to the third example is composed of two lenses, and thus has a compact and compact configuration in which the total length of the optical system is short. It can also be seen that, despite the two-lens configuration, various aberrations are well corrected and have excellent imaging performance.

  In the above-described embodiment, the following description can be appropriately adopted as long as the optical performance is not impaired.

  In the above embodiment, the two lens component configurations are shown as the projection lens, but the present invention can also be applied to other lens component configurations such as a three component, four component and the like. Further, a configuration in which a lens component or a lens group is added to the most object side, a configuration in which a lens component or a lens group is added to the most image side, or a lens component or a lens component between the first lens component L1 and the second lens component L2 A configuration in which a lens group is added may be used. The lens group indicates a portion having at least one lens component separated by an air interval that changes several times.

  Alternatively, a single lens component, a plurality of lens components, or a partial lens component may be moved in the optical axis direction so as to be a focusing lens component that performs focusing from an object at infinity to a near object. The focusing lens component can be applied to autofocus, and is also suitable for driving a motor for autofocus (using an ultrasonic motor or the like). In particular, it is preferable to focus on the entire lens system.

  Alternatively, the lens component or the partial lens component may be moved so as to have a component in a direction perpendicular to the optical axis, and may be an anti-vibration lens component that corrects image blur caused by camera shake. The movement may be rotational movement (swing) with a certain point on the optical axis as the rotation center. In particular, it is preferable that at least a part of the second lens component L2 is an anti-vibration lens component.

  The lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. It is preferable that the lens surface is a spherical surface or a flat surface because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. On the other hand, when the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite type non-spherical surface made of resin on the glass surface. Any aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  In addition, it is preferable that the aperture stop S is disposed on the projection side with respect to the first lens component L1. In the projection lens according to the present embodiment, when the light emitted from the image display element converges in a certain angle range and enters the projection lens, the aperture stop S is omitted or shifted to the first lens component L1 side. In this case, the optical system is further shortened, which is preferable.

  Each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high optical performance with high contrast.

  In addition, in order to make this invention intelligible, although demonstrated with the component requirement of embodiment, it cannot be overemphasized that this invention is not limited to this.

It is a block diagram of the projection lens which concerns on 1st Example. FIG. 6 is a diagram illustrating all aberrations of the projection lens according to Example 1; It is a block diagram of the projection lens which concerns on 2nd Example. It is an aberration diagram of the projection lens according to the second example. It is a block diagram of the projection lens which concerns on 3rd Example. It is an aberration diagram of the projection lens according to the third example.

Explanation of symbols

L1 First lens component L2 Second lens component S Aperture stop GB Parallel plane glass LCD Image display element

Claims (9)

In order from the projection side, the first lens component having a meniscus negative refractive power and the second lens component having a positive birefringent second refractive power substantially consist of two lenses ,
In order from the projection side toward the object side, the lens surface on the projection side of the first lens component, the lens surface on the object side of the first lens component, the lens surface on the projection side of the second lens component, and the second The lens surface on the object side of the lens component is all aspherical,
For the maximum effective diameter of the actual shape of the aspheric surface on the projection side of the first lens component, the curvature of the spherical surface when approximated to the spherical surface by the least square method is Rf11,
Rh11 is the curvature of the spherical surface when approximated to the spherical surface by the least square method for half the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the first lens component,
For the maximum effective diameter of the actual shape of the aspherical surface on the object side of the first lens component, the curvature of the spherical surface when approximated to the spherical surface by the least square method is Rf12,
When the curvature of the spherical surface when Rh12 is approximated to the spherical surface by the least square method with respect to half of the maximum effective diameter of the actual shape of the aspherical surface on the object side of the first lens component is 0.13 ≦ (Rf11−Rh11) /Rf11≦1.00
0.13 ≦ (Rf12−Rh12) /Rf12≦1.00
Projection lens characterized by satisfying the above conditions. For the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the second lens component, the curvature of the spherical surface when approximated to the spherical surface by the least square method is Rf21,
Rh21 is the curvature of the spherical surface when approximated to a spherical surface by the least square method for half the maximum effective diameter of the actual shape of the aspherical surface on the projection side of the second lens component,
For the maximum effective diameter of the actual shape of the aspherical surface on the object side of the second lens component, the curvature of the spherical surface when approximated to the spherical surface by the least square method is Rf22,
When the curvature of the spherical surface when approximated to a spherical surface by the least square method is Rh22 with respect to half of the maximum effective diameter of the actual shape of the aspherical surface on the object side of the second lens component, the following expression 0 ≦ (Rf21 -Rh21) /Rf21≤0.13
0 ≦ (Rf22−Rh22) /Rf22≦0.19
The projection lens according to claim 1, wherein the following condition is satisfied.   The projection lens according to claim 1, wherein the first lens component is a lens component including at least one plastic lens. When the Abbe number of the first lens component with respect to the d-line is νd1, the following equation 27 ≦ νd1 ≦ 35
The projection lens according to claim 1, wherein the following condition is satisfied. When the refractive index for the d-line of the first lens component is nd1, the following formula 1.50 ≦ nd1 ≦ 1.65
The projection lens according to claim 1, wherein the following condition is satisfied.   The projection lens according to claim 1, wherein the second lens component is a lens component made of at least one plastic lens. When the Abbe number of the second lens component with respect to the d-line is νd2, the following equation 53 ≦ νd2 ≦ 61
The projection lens according to claim 1, wherein the following condition is satisfied. When the refractive index for the d-line of the second lens component is nd2, the following formula 1.45 ≦ nd2 ≦ 1.60
The projection lens according to claim 1, wherein the following condition is satisfied.   The projection lens according to claim 1, wherein an aperture stop is provided closer to the projection side than the first lens component.

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