JP2007240934A - Projection lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact wide-angle projection lens having high optical performance. <P>SOLUTION: The projection lens 100 is constituted by arranging a first lens group 110 having negative refractive power, a second lens group 120 having positive refractive power and a third lens group 130 having positive refractive power in order from an enlargement side. Space between the first lens group 110 and the second lens group 120 is secured to be wide, and a mirror 180 for bending an optical path is arranged in the space. Thus, the optical path of the projection lens 100 is bent and the projection lens 100 is constituted to be compact. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a projection lens for enlarging and projecting an image displayed on a liquid crystal display element or a digital micromirror element on a screen.

  Conventionally, many projection lenses have been proposed for use in a projection type image display apparatus that enlarges and projects an image displayed on a liquid crystal display element, a digital micromirror element, or the like on a screen. In particular, in recent years, miniaturization of projection-type image display devices has progressed, and it has become necessary to increase the angle of the projection lens. Therefore, a so-called retrofocus type projection lens in which a lens group having a negative refractive power and a lens group having a positive refractive power are arranged in order from the enlargement side is often used (for example, Patent Document 1). , 2).

  With this type of projection lens, it is easy to widen the angle, and it is easy to ensure a long back focus compared to the focal length, so it is easy to place a dichroic prism, a total reflection prism, etc. between the lens and the image display element. There are advantages. In addition, when a dichroic prism or a total reflection prism is arranged between the projection lens and the image display element, the F number of the projection lens is suppressed in order to suppress a decrease in contrast of the image projected on the screen, color unevenness, and luminance unevenness. In addition, it is necessary to provide an optical system in which the side having a short conjugate length is telecentric and has a large peripheral light amount ratio.

  However, this type of projection lens has a problem that the total length tends to be long. Therefore, in order to solve such a problem, there is one in which the optical system is miniaturized by arranging a reflecting means such as a mirror between the lenses of a retrofocus type projection lens having a long overall length and bending the optical path. (For example, see Patent Document 3).

JP 2004-126280 A JP 2005-157153 A JP 2004-333688 A

  By the way, a projection type image display device using a projection lens has a problem that the depth of the casing itself is thicker than a video display device using a PDP (Plasma Display Panel) or a direct-view type LCD (Liquid Crystal Display). is there. In order to reduce the depth of the projection type image display apparatus, it is necessary to shorten the projection distance of the mounted projection lens and offset the optical axis. For this purpose, it is necessary to widen the angle of the projection lens.

  However, the projection lens disclosed in Patent Document 3 has a problem that the projection-type image display device is not wide enough to be thinned. Moreover, although the projection lens disclosed in Patent Document 2 has a wide angle, the lens configuration is complicated and the total length is long. Therefore, the projection lens disclosed in Patent Document 2 is also not suitable for thinning the projection type image display device.

  An object of the present invention is to provide a projection lens having a small size, a wide angle, and a high optical performance in order to solve the above-described problems caused by the prior art.

In order to solve the above-described problems and achieve the object, a projection lens according to a first aspect of the present invention has a first lens group having a negative refracting power and a positive refracting power arranged in order from the magnification side. And a second lens group. An interval is formed between the first lens group and the second lens group, and the following conditional expression is satisfied.
2.8 ≦ | f ₁ | /f≦3.2
−4.8 ≦ f ₂ / f ₁ ≦ −3.5
Here, f ₁ is the focal length of the first lens group, f ₂ is the focal length of the second lens group, and f is the focal length of the entire projection lens system.

  According to the first aspect of the present invention, it is possible to provide a small and wide-angle projection lens capable of ensuring long back focus and telecentricity and satisfactorily correcting various aberrations.

The projection lens according to the invention of claim 2 includes a first lens group having a negative refractive power and a second lens group having a positive refractive power, which are arranged in order from the magnification side, An interval is formed between the first lens group and the second lens group, and the following conditional expression is satisfied.
1.8 ≦ D ₁₂ / (f ₁ + f ₂ ) ≦ 2.7
Here, D ₁₂ is the distance between the first lens group and the second lens group, f ₁ is the focal length of the first lens group, and f ₂ is the focal length of the second lens group.

  According to the second aspect of the present invention, it is possible to provide a projection lens capable of securing a space for arranging the reflecting member in the optical system and correcting various aberrations satisfactorily.

The projection lens according to the invention of claim 3 includes a first lens group having a negative refractive power and a second lens group having a positive refractive power, which are arranged in order from the magnification side, An interval is formed between the first lens group and the second lens group, and the following conditional expression is satisfied.
2.8 ≦ | f ₁ | /f≦3.2
−4.8 ≦ f ₂ / f ₁ ≦ −3.5
1.8 ≦ D ₁₂ / (f ₁ + f ₂ ) ≦ 2.7
Where f ₁ is the focal length of the first lens group, f ₂ is the focal length of the second lens group, f is the focal length of the entire projection lens system, and D ₁₂ is the first lens group and the second lens. The distance between the groups is shown.

  According to the invention described in claim 3, the projection has a long back focus, telecentricity, and a small, wide-angle, high optical performance while securing a space for disposing the reflecting member in the optical system. A lens can be provided.

  A projection lens according to a fourth aspect of the present invention is the projection lens according to any one of the first to third aspects, wherein a reflecting member is disposed between the first lens group and the second lens group. The optical path is bent by the reflecting member.

  According to the fourth aspect of the present invention, it is possible to provide a compact projection lens in which the length of the optical system in the front-rear direction is shortened by bending the optical path by the reflecting member.

  According to the present invention, it is possible to provide a projection lens having high optical performance that is optimal for enlarging and projecting a high-definition image with a small size and a wide angle.

  Hereinafter, preferred embodiments of the projection lens according to the present invention will be described in detail.

  A projection lens according to an embodiment of the present invention includes, in order from the magnification side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens having a positive refractive power. A group is arranged. In order to correct various aberrations satisfactorily, an aspherical surface is formed on at least one surface of the lens constituting the first lens group.

  An object of the present invention is to provide a projection lens having a small size, a wide angle, and high optical performance. Therefore, in order to achieve this purpose, various conditions as shown below are set.

First, it is preferable that the projection lens of this embodiment satisfies the following conditional expression when the focal length of the first lens unit is f ₁ and the focal length of the entire system is f.
2.8 ≦ | f ₁ | /f≦3.2 (1)

Conditional expression (1) defines the ratio of the focal length f ₁ of the first lens group to the focal length f of the entire projection lens system according to this embodiment. Satisfying conditional expression (1) makes it possible to ensure long back focus and telecentricity and to correct various aberrations satisfactorily. If the value of | f ₁ | / f exceeds 3.2, the focal length of the first lens unit becomes long, and it becomes difficult to ensure long back focus and telecentricity. On the other hand, if the value of | f ₁ | / f is less than 2.8, the focal length of the first lens group becomes short, and it becomes difficult to correct various aberrations.

Further, the projection lens of this embodiment, the focal length of the second lens group when the f _2, it is preferable to satisfy the following condition.
−4.8 ≦ f ₂ / f ₁ ≦ −3.5 (2)

Conditional expression (2) defines the ratio between the focal length f ₁ of the first lens unit and the focal length f ₂ of the second lens unit in the projection lens according to this embodiment. Satisfying conditional expression (2) makes it possible to reduce the size, widen the angle, and correct various aberrations. If the value of f ₂ / f ₁ exceeds −3.5, the focal length of the entire optical system is not reduced, and the projection lens cannot be widened. On the other hand, when the value of f ₂ / f ₁ is less than −4.8, the focal length f ₂ of the second lens group becomes too large relative to the focal length f ₁ of the first lens group, and various aberrations are corrected. It becomes difficult.

Furthermore, the distance between the second lens group and the third lens group when the D _12, it is preferable to satisfy the following condition.
1.8 ≦ D ₁₂ / (f ₁ + f ₂ ) ≦ 2.7 (3)

The conditional expression (3), the focal length f ₁ and the focal point of the second lens group length f the sum of ₂ and the first lens group second of the first lens group in the projection lens according to this embodiment This defines the ratio of the distance D _{12 to} the lens group. Satisfying the conditional expression (3) makes it possible to secure a space for disposing the reflecting member in the optical system and correct various aberrations. When the value of D ₁₂ / (f ₁ + f ₂ ) exceeds 2.7, the focal length of the first lens group and the second lens group becomes small, and it becomes difficult to correct various aberrations. On the other hand, when the value of D ₁₂ / (f ₁ + f ₂ ) is less than 1.8, the distance between the first lens group and the second lens group becomes too small, and the first lens group and the second lens It becomes impossible to secure a space for arranging a reflecting member (for example, a mirror or a prism) for folding the optical path between the group. When such a state occurs, when the projection lens is mounted on the projection type image display device, the depth of the projection type image display device is reduced.

  The projection lens according to the present embodiment satisfies any one of the conditional expressions (1) to (3), thereby producing effects specific to the conditional expressions (1) to (3). Projection lens suitable for mounting on a flat-panel image display device. That is, by satisfying conditional expression (1), it is possible to realize a projection lens capable of ensuring a long back focus and telecentricity and satisfactorily correcting various aberrations. By satisfying conditional expression (2), it is possible to realize a projection lens capable of reducing the size, widening the angle, and correcting various aberrations. By satisfying conditional expression (3), the optical path can be bent by inserting the reflecting member into the optical system while maintaining the optical performance, and a smaller projection lens can be realized. However, by satisfying all the conditional expressions at the same time rather than only one conditional expression, a projection lens that contributes to the thinning of the projection type image display device can be obtained.

  Since the projection lens of this embodiment has optical performance that can be adapted to the projection type image display device, it is basically composed of three groups. However, when further downsizing of the optical system is desired, the optical system can be configured by only the first lens group and the second lens group that satisfy the conditional expressions (1) to (3). If the first lens group and the second lens group satisfy the conditional expressions (1) to (3), optical performance that can withstand actual use can be obtained.

  In addition, if the range of each numerical value shown by said conditional expression (1)-(3) is a value near the said numerical value, the effect anticipated by this invention will be acquired.

  As described above, according to this embodiment, it is possible to provide a projection lens that is small, wide-angle, and has high optical performance while ensuring long back focus and telecentricity. This projection lens is optimal for a projection-type image display device that is required to be smaller in recent years.

  Examples of the projection lens according to the present invention will be described below.

Example 1
FIG. 1 is a cross-sectional view along the optical axis showing the configuration of the projection lens according to the first embodiment. The projection lens 100 includes a first lens group 110 having a negative refractive power, a second lens group 120 having a positive refractive power, and a third lens having a positive refractive power in order from the enlargement side (left side in the figure). A group 130 is arranged. A stop 140 is disposed between the second lens group 120 and the third lens group 130. A prism 160 and a cover glass 170 are arranged between the third lens group 130 and the image display element 150. In addition, the cover glass 170 is arrange | positioned as needed and can also be abbreviate | omitted depending on the case.

  The first lens group 110 includes a negative lens 111, a negative lens 112, and a negative lens 113 arranged in this order from the magnification side. Aspherical surfaces are formed on both surfaces of the negative lens 111.

  The second lens group 120 includes a positive lens 121 and a positive lens 122 arranged in order from the magnification side.

  The third lens group 130 includes a positive lens 131, a negative lens 132, a positive lens 133, a negative lens 134, a negative lens 135, a positive lens 136, and a positive lens 137 in order from the magnification side. The positive lens 131 and the negative lens 132, the positive lens 133 and the negative lens 134, and the negative lens 135 and the positive lens 136 are all cemented.

  A mirror 180 is disposed between the first lens group 110 and the second lens group 120. The arrangement of the mirror 180 is facilitated by satisfying the conditional expression (3). By disposing the mirror 180 between the first lens group 110 and the second lens group 120, the optical path of the projection lens 100 can be bent. A prism may be arranged instead of the mirror 180.

  FIG. 2 is a cross-sectional view along the optical axis showing the configuration of the projection lens of Example 1 when used. As shown in FIG. 2, the projection lens 100 of Example 1 can be configured to be compact by bending the optical path by disposing a mirror 180 between the first lens group 110 and the second lens group 120. . In this way, it is possible to realize a small projection lens that is optimal for a projection type image display apparatus that is becoming smaller.

  Various numerical data relating to the projection lens according to Example 1 will be described below.

Focal length (f) of the entire projection lens 100 system = 4.22
Distance from first surface of projection lens 100 to screen for projecting image = 459.0
Focal length (f ₁ ) = (− 11.84) of the first lens group 110
Focal length of second lens group 120 (f ₂ ) = (56.78)
Distance between first lens group 110 and second lens group 120 (D ₁₂ ) = 87.729
F number = 2.0
Half angle of view (ω) = 57.1 °

(Condition (1))
| F ₁ | /f=2.81

(Condition (2))
f ₂ / f ₁ = -4.80

(Condition (3))
D ₁₂ / (f ₁ + f ₂ ) = 1.86

r ₁ = 113.865 (aspherical surface)
d ₁ = 10.000 nd ₁ = 1.52470 νd ₁ = 56.20
r ₂ = 24.699 (aspherical surface)
d ₂ = 18.643
r ₃ = 69.735
d ₃ = 3.000 nd ₂ = 1.58913 νd ₂ = 61.18
r ₄ = 28.058
d ₄ = 14.992
r ₅ = -1058.202
d ₅ = 2.000 nd ₃ = 1.77250 νd ₃ = 49.60
r ₆ = 27.407
d ₆ = 62.600
r ₇ = ∞ (mirror)
d ₇ = 25.129
r ₈ = 72.455
d ₈ = 10.048 nd ₄ = 1.80610 νd ₄ = 33.27
r ₉ = 241.397
d ₉ = 2.057
r ₁₀ = 40.387
d ₁₀ = 7.139 nd ₅ = 1.74400 νd ₅ = 44.79
r ₁₁ = 81.746
d ₁₁ = 20.911
r ₁₂ = ∞ (aperture)
d ₁₂ = 6.218
r ₁₃ = 54.811
d ₁₃ = 3.750 nd ₆ = 1.48749 νd ₆ = 70.21
r ₁₄ = -38.125
d ₁₄ = 1.200 nd ₇ = 1.83400 νd ₇ = 37.17
r ₁₅ = 47.432
d ₁₅ = 0.500
r ₁₆ = 33.809
d ₁₆ = 5.488 nd ₈ = 1.49700 νd ₈ = 81.61
r ₁₇ = -16.128
d ₁₇ = 1.500 nd ₉ = 1.80610 νd ₉ = 40.95
r ₁₈ = -50.278
d ₁₈ = 5.288
r ₁₉ = 69.725
d ₁₉ = 1.500 nd ₁₀ = 1.80610 νd ₁₀ = 40.95
r ₂₀ = 21.478
d ₂₀ = 5.751 nd ₁₁ = 1.49700 νd ₁₁ = 81.61
r ₂₁ = -41.545
d ₂₁ = 0.500
r ₂₂ = 24.039
d ₂₂ = 5.581 nd ₁₂ = 1.49700 νd ₁₂ = 81.61
r ₂₃ = -67.237
d ₂₃ = 5.600
r ₂₄ = ∞
d ₂₄ = 12.000 nd ₁₃ = 1.51680 νd ₁₃ = 64.20
r ₂₅ = ∞
d ₂₅ = 3.000
r ₂₆ = ∞
d ₂₆ = 3.000 nd ₁₄ = 1.50847 νd ₁₄ = 60.83
r ₂₇ = ∞
d ₂₇ = 0.483

Cone coefficient (ε) and aspheric coefficient (A, B, C, D, E)
(First side)
ε = 3.9725
A = 0
B = 3.49728 × 10 ⁻⁷ , C = −9.31352 × 10 ⁻¹² ,
D = -1.10711 × 10 ^-14 , E = 4.85214 × 10 ^-18
(Second side)
ε = 0.1161
A = 0
B = 2.50882 × 10 ⁻⁷ , C = −4.883743 × 10 ⁻¹⁰ ,
D = 1.36780 × 10 ⁻¹³ , E = 5.01173 × 10 ⁻¹⁷

  FIG. 3 is an aberration diagram of the projection lens according to Example 1. FIG. 3 shows spherical aberration, astigmatism, and distortion on the shorter conjugate length side in a 50-inch screen size.

  FIG. 4 is a diagram illustrating a usage example of the projection lens according to the first embodiment. FIG. 4 shows an example in which the projection lens 100 of the first embodiment is mounted on the projection type image display apparatus 400. The projection lens 100 reflects the image displayed on the image display element 150 to the rear mirror 401 and enlarges and projects it on the screen 402. When the projection lens 100 is mounted on the projection-type image display device 400, the mirror 180 can be arranged in the optical system so that the optical path can be bent to form a compact structure. The depth of 403 can be reduced.

(Example 2)
FIG. 5 is a cross-sectional view along the optical axis showing the configuration of the projection lens according to the second embodiment. The projection lens 500 includes a first lens group 510 having a negative refractive power, a second lens group 520 having a positive refractive power, and a third lens having a positive refractive power in order from the enlargement side (left side in the figure). A group 530 is arranged and configured. A stop 540 is disposed between the second lens group 520 and the third lens group 530. A prism 560 and a cover glass 570 are arranged between the third lens group 530 and the image display element 550. In addition, the cover glass 570 is arrange | positioned as needed and can also be abbreviate | omitted depending on the case.

  The first lens group 510 includes a negative lens 511, a negative lens 512, and a negative lens 513 arranged in order from the magnification side. Aspheric surfaces are formed on both surfaces of the negative lens 511.

  The second lens group 520 includes a positive lens 521 and a positive lens 522 arranged in order from the magnification side.

  The third lens group 530 includes a negative lens 531, a positive lens 532, a positive lens 533, a negative lens 534, a negative lens 535, a positive lens 536, and a positive lens 537 in order from the magnification side. The negative lens 531 and the positive lens 532, the positive lens 533 and the negative lens 534, and the negative lens 535 and the positive lens 536 are all cemented.

  A mirror 580 is disposed between the first lens group 510 and the second lens group 520. The arrangement of the mirror 580 is facilitated by satisfying the conditional expression (3). By disposing the mirror 580 between the first lens group 510 and the second lens group 520, the optical path of the projection lens 500 can be bent as in the first embodiment. Therefore, similarly to the projection lens 100 of the first embodiment, the projection lens 500 of the second embodiment can be used for a projection-type image display device, thereby facilitating a reduction in the thickness of the projection-type image display device. A prism may be arranged in place of the mirror 580.

  Various numerical data relating to the projection lens according to Example 2 will be described below.

Focal length (f) of the entire projection lens 500 system = 4.24
Distance from first surface of projection lens 500 to screen to project image = 458.8
Focal length (f ₁ ) = (− 12.76) of the first lens group 510
Focal length (f ₂ ) = (45.35) of the second lens group 520
Distance between first lens group 510 and second lens group 520 (D ₁₂ ) = 111.84
F number = 2.0
Half angle of view (ω) = 58.8 °

(Condition (1))
| F ₁ | /f=3.01

(Condition (2))
f ₂ / f ₁ = -3.55

(Condition (3))
D ₁₂ / (f ₁ + f ₂ ) = 2.69

r ₁ = 136.676 (aspherical surface)
d ₁ = 10.000 nd ₁ = 1.52470 νd ₁ = 56.20
r ₂ = 25.755 (aspherical surface)
d ₂ = 21.146
r ₃ = 79.766
d ₃ = 3.000 nd ₂ = 1.51633 νd ₂ = 64.15
r ₄ = 29.314
d ₄ = 15.825
r ₅ = -3620.294
d ₅ = 2.000 nd ₃ = 1.69680 νd ₃ = 55.53
r ₆ = 27.664
d ₆ = 76.228
r ₇ = ∞ (mirror)
d ₇ = 35.612
r ₈ = 40.268
d ₈ = 6.408 nd ₄ = 1.83400 νd ₄ = 37.17
r ₉ = 95.592
d ₉ = 5.868
r ₁₀ = 39.711
d ₁₀ = 6.667 nd ₅ = 1.72000 νd ₅ = 50.25
r ₁₁ = 87.175
d ₁₁ = 11.565
r ₁₂ = ∞ (aperture)
d ₁₂ = 3.078
r ₁₃ = -54.866
d ₁₃ = 5.801 nd ₆ = 1.80610 νd ₆ = 33.27
r ₁₄ = 20.047
d ₁₄ = 4.263 nd ₇ = 1.48749 νd ₇ = 70.21
r ₁₅ = -40.015
d ₁₅ = 0.285
r ₁₆ = 21.976
d ₁₆ = 5.038 nd ₈ = 1.49700 νd ₈ = 81.61
r ₁₇ = -25.506
d ₁₇ = 1.500 nd ₉ = 1.78590 νd ₉ = 44.19
r ₁₈ = -136.828
d ₁₈ = 9.073
r ₁₉ = -131.471
d ₁₉ = 1.500 nd ₁₀ = 1.78590 νd ₁₀ = 44.19
r ₂₀ = 23.425
d ₂₀ = 5.946 nd ₁₁ = 1.49700 νd ₁₁ = 81.61
r ₂₁ = -34.196
d ₂₁ = 1.449
r ₂₂ = 17.214
d ₂₂ = 6.052 nd ₁₂ = 1.49700 νd ₁₂ = 81.61
r ₂₃ = 291.346
d ₂₃ = 1.000
r ₂₄ = ∞
d ₂₄ = 10.000 nd ₁₃ = 1.51680 νd ₁₃ = 64.20
r ₂₅ = ∞
d ₂₅ = 2.000
r ₂₆ = ∞
d ₂₆ = 3.000 nd ₁₄ = 1.50847 νd ₁₄ = 60.83
r ₂₇ = ∞
d ₂₇ = 0.483

Cone coefficient (ε) and aspheric coefficient (A, B, C, D, E)
(First side)
ε = 4.8017
A = 0
B = 2.81499 × 10 ⁻⁷ , C = -1.29719 × 10 ⁻¹³ ,
D = -9.13093 × 10 ^-16 , E = 9.89347 × 10 ^-19
(Second side)
ε = 0.0450
A = 0
B = 1.43297 × 10 ⁻⁷ , C = 2.376 × 10 ⁻¹¹ ,
D = 1.10946 × 10 ⁻¹³ , E = 4.83130 × 10 ⁻¹⁷

  FIG. 6 is an aberration diagram of the projection lens according to Example 2. FIG. 6 shows spherical aberration, astigmatism, and distortion on the short side of the conjugate length in a 50-inch screen size.

(Example 3)
FIG. 7 is a cross-sectional view along the optical axis showing the configuration of the projection lens according to the third example. The projection lens 700 includes a first lens group 710 having a negative refractive power, a second lens group 720 having a positive refractive power, and a third lens having a positive refractive power in order from the magnification side (left side in the figure). A group 730 is arranged and configured. A diaphragm 740 is disposed between the second lens group 720 and the third lens group 730. A prism 760 and a cover glass 770 are disposed between the third lens group 730 and the image display element 750. In addition, the cover glass 770 is arrange | positioned as needed and can also be abbreviate | omitted depending on the case.

  The first lens group 710 includes a negative lens 711, a negative lens 712, and a negative lens 713 arranged in order from the magnification side. An aspheric surface is formed on both surfaces of the negative lens 711.

  The second lens group 720 includes a positive lens 721 and a positive lens 722 arranged in order from the magnification side.

  The third lens group 730 includes a negative lens 731, a positive lens 732, a positive lens 733, a negative lens 734, a negative lens 735, a positive lens 736, and a positive lens 737 in order from the magnification side. The negative lens 731 and the positive lens 732, the positive lens 733 and the negative lens 734, and the negative lens 735 and the positive lens 736 are all cemented.

  Further, a mirror 780 is disposed between the first lens group 710 and the second lens group 720. The arrangement of the mirror 780 is facilitated by satisfying the conditional expression (3). By disposing the mirror 780 between the first lens group 710 and the second lens group 720, the optical path of the projection lens 700 can be bent as in the first embodiment. Therefore, similarly to the projection lens 100 of the first embodiment, the projection lens 700 of the third embodiment can be used for a projection type image display device, thereby facilitating a reduction in the thickness of the projection type image display device. Note that a prism may be arranged instead of the mirror 780.

  Various numerical data related to the projection lens according to Example 3 are shown below.

Focal length (f) of the entire projection lens 700 system = 4.21
Distance from first surface of projection lens 700 to screen for projecting image = 456.9
Focal length (f ₁ ) = (− 13.42) of the first lens group 710
Focal length (f ₂ ) = (52.74) of the second lens group 720
Distance between first lens group 710 and second lens group 720 (D ₁₂ ) = 113.678
F number = 2.0
Half angle of view (ω) = 57.0 °

(Condition (1))
| F ₁ | /f=3.19

(Condition (2))
f ₂ / f ₁ = -3.95

(Condition (3))
_{D 12 / (f 1 + f} 2) = 2.26

r ₁ = 137.485 (aspherical surface)
d ₁ = 10.000 nd ₁ = 1.52470 νd ₁ = 56.20
r ₂ = 26.807 (aspherical surface)
d ₂ = 20.566
r ₃ = 69.272
d ₃ = 3.000 nd ₂ = 1.58913 νd ₂ = 61.18
r ₄ = 29.854
d ₄ = 15.816
r ₅ = 1226.319
d ₅ = 2.000 nd ₃ = 1.77250 νd ₃ = 49.60
r ₆ = 30.702
d ₆ = 77.131
r ₇ = ∞ (mirror)
d ₇ = 36.547
r ₈ = 41.618
d ₈ = 6.504 nd ₄ = 1.80610 νd ₄ = 33.27
r ₉ = 97.045
d ₉ = 7.207
r ₁₀ = 41.959
d ₁₀ = 5.753 nd ₅ = 1.67270 νd ₅ = 32.10
r ₁₁ = 79.332
d ₁₁ = 12.121
r ₁₂ = ∞ (aperture)
d ₁₂ = 3.861
r ₁₃ = -57.377
d ₁₃ = 5.625 nd ₆ = 1.80610 νd ₆ = 33.27
r ₁₄ = 21.764
d ₁₄ = 4.041 nd ₇ = 1.48749 νd ₇ = 70.21
r ₁₅ = -40.520
d ₁₅ = 0.290
r ₁₆ = 24.277
d ₁₆ = 5.813 nd ₈ = 1.49700 νd ₈ = 81.61
r ₁₇ = -24.938
d ₁₇ = 1.500 nd ₉ = 1.78590 νd ₉ = 44.19
r ₁₈ = -137.057
d ₁₈ = 7.069
r ₁₉ = -261.792
d ₁₉ = 1.500 nd ₁₀ = 1.78590 νd ₁₀ = 44.19
r ₂₀ = 25.598
d ₂₀ = 8.094 nd ₁₁ = 1.49700 νd ₁₁ = 81.61
r ₂₁ = -32.523
d ₂₁ = 0.446
r ₂₂ = 22.662
d ₂₂ = 4.783 nd ₁₂ = 1.49700 νd ₁₂ = 81.61
r ₂₃ = -348.095
d ₂₃ = 5.600
r ₂₄ = ∞
d ₂₄ = 12.000 nd ₁₃ = 1.51680 νd ₁₃ = 64.20
r ₂₅ = ∞
d ₂₅ = 3.000
r ₂₆ = ∞
d ₂₆ = 3.000 nd ₁₄ = 1.50847 νd ₁₄ = 60.83
r ₂₇ = ∞
d ₂₇ = 0.483

Cone coefficient (ε) and aspheric coefficient (A, B, C, D, E)
(First side)
ε = 4.7943
A = 0
B = 2.90402 × 10 ⁻⁷ , C = 7.80252 × 10 ⁻¹³ ,
D = -2.24878 × 10 ^-15 , E = 1.65827 × 10 ^-18
(Second side)
ε = 0.0665
A = 0
B = -2.15549 × 10 ^-8 , C = -1.27820 × 10 ^-10 ,
D = 2.92055 × 10 ⁻¹³ , E = 1.22756 × 10 ⁻¹⁶

  FIG. 8 is an aberration diagram of the projection lens according to Example 3. FIG. 8 shows spherical aberration, astigmatism, and distortion on the shorter conjugate length side in a 50-inch screen size.

In the above numerical data, r ₁ , r ₂ ,... Are the radii of curvature of the lenses and the diaphragm surface, and d ₁ , d ₂ ,. .., Nd ₁ , nd ₂ ,... Represents the refractive index of each lens in the d-line, and νd ₁ , νd ₂ ,.

  Each of the aspherical shapes is expressed by the following expression when the X axis is in the optical axis direction, the H axis is in the direction perpendicular to the optical axis, and the light traveling direction is positive.

  Here, r is a paraxial radius of curvature, and A, B, C, D, and E are second-order, fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients, respectively.

  As described above, according to the projection lenses of the first, second, and third embodiments, the projection lens having a small size, a wide angle, and high optical performance by satisfying the conditional expressions (1) to (3). Can be provided. In other words, the projection half field angle is about 57 degrees, the F number is about 2.0, and it is bright with a wide angle, approximately telecentricity, the peripheral light quantity ratio is as high as 70% or more, and various aberrations can be corrected well. A lens can be provided. This projection lens is optimal for a projection-type image display device that is required to be smaller in recent years.

  As described above, the projection lens of the present invention is useful for a projection-type image display device that requires a small size and a wide angle, and is particularly suitable when high optical performance is required.

FIG. 3 is a cross-sectional view along the optical axis showing the configuration of the projection lens according to Example 1; FIG. 3 is a cross-sectional view along the optical axis showing the configuration when the projection lens of Example 1 is used. FIG. 4 is an aberration diagram of the projection lens according to Example 1; FIG. 3 is a diagram illustrating an example of use of the projection lens of Example 1. FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a projection lens according to Example 2. FIG. 6 is an aberration diagram of the projection lens according to Example 2; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of the projection lens according to Example 3; FIG. 10 is an aberration diagram of the projection lens according to Example 3;

Explanation of symbols

100, 500, 700 Projection lens 110, 510, 710 First lens group 121, 122, 131, 133, 136, 137, 521, 522, 532, 533, 536, 537, 721, 722, 732, 733, 736 737 positive lens 111,112,113,132,134,135,511,512,513,531,534,535,711,712,713,731,734,735 negative lens 120,520,720 second lens group 130 , 530, 730 Third lens group 140, 540, 740 Aperture 150, 550, 750 Image display element 160, 560, 760 Prism 170, 570, 770 Cover glass 180, 580, 780 Mirror 400 Projection type image display device 401 Rear mirror 402 screen 403 Enclosure

Claims (4)

A first lens group having a negative refractive power, and a second lens group having a positive refractive power, which are arranged in order from the magnification side,
A projection lens characterized in that an interval is formed between the first lens group and the second lens group and the following conditional expression is satisfied.
2.8 ≦ | f ₁ | /f≦3.2
−4.8 ≦ f ₂ / f ₁ ≦ −3.5
Here, f ₁ is the focal length of the first lens group, f ₂ is the focal length of the second lens group, and f is the focal length of the entire projection lens system. A first lens group having a negative refractive power, and a second lens group having a positive refractive power, which are arranged in order from the magnification side,
A projection lens characterized in that an interval is formed between the first lens group and the second lens group and the following conditional expression is satisfied.
1.8 ≦ D ₁₂ / (f ₁ + f ₂ ) ≦ 2.7
Here, D ₁₂ is the distance between the first lens group and the second lens group, f ₁ is the focal length of the first lens group, and f ₂ is the focal length of the second lens group. A first lens group having a negative refractive power, and a second lens group having a positive refractive power, which are arranged in order from the magnification side,
A projection lens characterized in that an interval is formed between the first lens group and the second lens group and the following conditional expression is satisfied.
2.8 ≦ | f ₁ | /f≦3.2
−4.8 ≦ f ₂ / f ₁ ≦ −3.5
1.8 ≦ D ₁₂ / (f ₁ + f ₂ ) ≦ 2.7
Where f ₁ is the focal length of the first lens group, f ₂ is the focal length of the second lens group, f is the focal length of the entire projection lens system, and D ₁₂ is the first lens group and the second lens. The distance between the groups is shown. The projection according to claim 1, wherein a reflection member is disposed between the first lens group and the second lens group, and an optical path is bent by the reflection member. lens.

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