JP2012002906A - Projection lens and projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection lens with good telecentricity which can be downsized with a small number of lenses and is bright, has a wide field angle and a long air gap for inserting an optical element.SOLUTION: A projection lens has, seen from the projection surface, a first lens groups with negative refractive power, a second lens group with positive refractive power, and a third lens group with positive refractive power. The first lens group is made from a 1a lens and a 1b lens group having one single negative refractive power seen from the projection surface. The 1b lens group is made from one positive lens and one negative lens seen from projection surface and satisfies the following conduction formula: -2.0<f/f<-0.7 wherein f: composite focal distance of the first lens group f: composite focal distance of the second lens group.

Description

  The present invention relates to a projection lens suitable for a projection apparatus equipped with a light valve such as a reflective liquid crystal or DMD (digital micromirror device), and a projection apparatus equipped with the projection lens.

  Conventionally, using a light valve such as a reflective liquid crystal display device or a DMD display device, in order to insert a reflective optical element such as a polarization separation element of a retrofocus type, a display element and a lens closer to the projection surface than the display element Projectors that have a relatively long air gap (hereinafter referred to as a reflective optical element insertion gap) are widely used.

  In recent years, attempts have been made to reduce the size of projectors, and various projection lenses have been devised in which the number of lenses is small and a large screen can be obtained.

  Further, in order to obtain a high-definition image, it is necessary to increase the number of lenses, which is expensive.

  Further, although it is possible to improve the performance by reducing the number of lenses, the brightness becomes darker and the angle of view becomes narrower.

  A projection lens corresponding to such a problem is disclosed in a patent publication (for example, see Patent Documents 1, 2, and 3).

JP-A-6-317742 JP 2007-279384 A JP 2008-145802 A

  However, the projection lens of Patent Document 1 has a small number of lenses and various aberrations are corrected, but has a narrow field angle and a dark optical system.

  Further, in the projection lens of Patent Document 2, the air space between the first lens group and the second lens group is widened, and although a good projection image can be obtained, the apparatus becomes large.

  Furthermore, in the projection lens of Patent Document 3, the lens diameter is reduced, and a good projection image can be obtained by increasing the number of lenses. However, the cost is increased by increasing the number of lenses. .

  The present invention has been made in view of such a problem, and can be downsized with a small number of lenses, has a bright and wide angle of view, has a long reflective optical element insertion interval, and has excellent telecentricity, and the projection lens. An object of the present invention is to provide a projection apparatus including the above.

  The above object is achieved by the invention described below.

  [1] The projection lens of the present invention includes, in order from the projection surface side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. The first lens group includes one 1a lens and 1b lens group having negative refractive power from the projection surface side, and the 1b lens group includes one positive lens and one lens from the projection surface side. And satisfying the following conditional expression.

−2.0 <f ₁ / f ₂ <−0.7 (1)
However,
f ₁ : Combined focal length of the first lens group f ₂ : Combined focal length of the second lens group The projection lens of the present invention has a retrofocus type lens configuration, so that the first lens group and the second lens It is possible to increase the combined back focus of the group and increase the air space between the second lens group and the third lens group. In a projection apparatus using a light valve such as a reflective liquid crystal or DMD, an air space for installing a polarization separation element is required. For this reason, it is possible to install a polarization separation element between the second lens group and the third lens group. Further, the 1b lens group is composed of one positive lens and one negative lens from the magnification side, thereby correcting chromatic aberration and obtaining good performance.

  On the other hand, if the value of conditional expression (1) is below the lower limit, the refractive power of the first lens group becomes too weak, the air gap between the first lens group and the second lens group becomes large, and the apparatus becomes large. On the other hand, if the value of conditional expression (1) exceeds the upper limit, the refractive power of the first lens group becomes too strong, making it difficult to correct various aberrations. Furthermore, since the error sensitivity of the first lens group is increased, mass productivity is impaired. By satisfying conditional expression (1), it is possible to reduce the size of the apparatus and increase the productivity.

  More desirably, it is preferable to be within the range of the following formula.

−1.6 <f ₁ / f ₂ <−0.9
The 1b lens group is more preferably a cemented lens.

  By using a cemented lens for the 1b lens group, the first lens group can be made into a two-group structure, and an error that occurs when assembling into the lens barrel as compared with the case where it is composed of three lenses. Factors can be reduced and productivity can be improved.

  [2] The projection lens described in 1 satisfies the following conditional expression.

−2.5 <f _1a /f<−1.0 (2)
However,
f _1a : focal length of the 1a lens f: focal length of the entire system When the value of the conditional expression (2) is below the lower limit, the negative refractive power of the 1a lens becomes too weak, so the first lens group and the second lens group Therefore, it becomes difficult to obtain an air space for installing the polarization separation element. On the other hand, if the value of conditional expression (2) exceeds the upper limit, the negative refractive power becomes too strong, and aberrations such as astigmatism, distortion, and lateral chromatic aberration increase, making it difficult to obtain good optical performance. Become. By satisfying conditional expression (2), it is possible to obtain an appropriate reflection type optical element insertion interval for installing the polarization separation element while obtaining good optical performance.

  [3] The projection lens described in 1 satisfies the following conditional expression.

0.4 <d ₁₂ / f ₁₂ <0.8 (3)
However,
d ₁₂ : air distance between the first lens group and the second lens group f ₁₂ : combined focal length of the first lens group and the second lens group When the value of the conditional expression (3) is below the lower limit, the first Since the distance between the lens group and the second lens group becomes too small and the powers of the first lens group and the second lens group become strong, it becomes difficult to correct various aberrations. If the upper limit is exceeded, good optical performance can be obtained, but the air space between the first lens group and the second lens group becomes too large, resulting in an increase in size of the apparatus. By satisfying conditional expression (3), it is possible to reduce the size of the apparatus and to obtain good optical performance.

  [4] In the projection lens according to any one of 1 to 3, the second lens group has an aperture stop closest to the projection surface, and at least one negative lens and one lens in order from the projection surface. The positive lens is provided.

  With the above-described configuration, the lens groups before and after the aperture are symmetrically configured such as a positive lens, a negative lens, an aperture, a negative lens, and a positive lens. As a result, it is possible to satisfactorily correct off-axis aberrations such as coma and chromatic aberration.

  [5] The projection lens described in any one of 1 to 4 is characterized in that the positive lens and the negative lens of the 1b lens group are cemented with each other and satisfy the following conditional expression.

0.2 <n _d1b1 −n _d1b2 (4)
−65 <ν _d1b1 −ν _d1b2 <−30 (5)
However,
_n d1b1: the 1b lens group having a positive lens having a refractive index _n d1b2: the refractive index of the negative lens of the 1b lens group _ν d1b1: the 1b lens group having a positive lens Abbe number _ν d1b2: the negative lens of the 1b lens group Abbe number If the value of conditional expression (4) is less than the lower limit, the difference in refractive index becomes too small, the radius of curvature of each lens becomes small, and it is difficult to process and the cost is high. In addition, the error sensitivity becomes high, and it is easily affected by errors during assembly. Also, if the value of conditional expression (5) is below the lower limit, the axial chromatic aberration is such that the d line becomes under the g line, and the d line has a higher image height than the g line. Lateral chromatic aberration occurs. If the value of conditional expression (5) exceeds the upper limit, the above is reversed, which is also not preferable. When the value of conditional expression (5) exceeds the lower limit or the upper limit, it is difficult to correct axial chromatic aberration and lateral chromatic aberration that occur in the first lens group.

  [6] The projection lens described in any one of 1 to 5 satisfies the following conditional expression.

2.0 <f ₃ /f<3.0 (6)
However,
f ₃ : Focal length of the third lens group In a general projection system, when light is incident on the display element at an angle, the color changes depending on the polarization characteristics, and the reflectance deteriorates. In order to prevent this, good telecentricity on the reduction side is necessary. Conditional expression (6) is an expression for defining the reduction-side telecentricity. When the value of conditional expression (6) is below the lower limit, the reduction-side telecentricity tends to collapse, and further, the curvature of field, etc. It becomes difficult to correct the off-axis aberration. If the value of conditional expression (6) exceeds the upper limit, not only the telecentricity will be lost, but it will be difficult to converge the light flux from the display element, and the lens diameters of the first lens group and the second lens group will increase. This hinders downsizing of the device. By satisfying conditional expression (6), it is possible to secure good telecentricity on the reduction side and prevent the lens diameter from becoming large.

  More desirably, it is preferable to be within the range of the following formula.

2.2 <f ₃ /f<2.7
[7] The projection lens described in any one of 1 to 6 is characterized in that focusing is performed by moving the first lens group in the optical axis direction.

  When only the first lens group is moved during focusing, the change in astigmatism with respect to the change in the distance between the first lens group and the second lens group can be reduced, and performance deterioration during focusing can be prevented. is there. In addition, since the number of lenses in the movable group is small and the load on the actuator can be reduced, power consumption can be reduced and the actuator itself can be downsized. This allows further miniaturization of the device.

  [8] The projection lens described in any one of 1 to 6 is characterized in that focusing is performed by moving the second lens group in the optical axis direction.

  When only the second lens group is moved during focusing, it is difficult for dust from the outside to enter, and it is possible to prevent deterioration of the projected image due to dust. Further, when a projection apparatus using the projection lens of the present invention is used, there is a possibility that the user touches the first lens group or an unexpected impact is applied to the first lens group. Even in such a case, since the first lens group is fixed, it is possible to prevent the focusing mechanism from being damaged when an impact is applied to the first lens group.

  [9] The projection lens described in any one of 1 to 6 is characterized in that focusing is performed by moving the first lens group and the second lens group in the optical axis direction.

  If the first lens group and the second lens group are simultaneously moved during focusing, a change in astigmatism with respect to a change in the distance between the second lens group and the third lens group can be reduced, and performance degradation during focusing can be reduced. It is possible to prevent.

  [10] In the projection lens described in any one of 1 to 9, the 1b lens group has a positive refractive power.

  Since the 1b lens group has a positive refractive power, the first lens group has a configuration of a 1a lens having a negative refractive power on the enlargement side and a 1b lens group having a positive refractive power. Thereby, since the first lens group is a combination of a negative lens and a positive lens, it is possible to obtain good optical performance.

  [11] In the projection lens described in any one of 1 to 10, the third lens group includes one positive lens.

  By constituting the third lens group from a single positive lens, a good telecentric property on the reduction side is secured with a minimum number of lenses, and the lens diameter of the second lens group is reduced from the first lens group. It becomes possible.

  [12] The projection lens described in any one of 1 to 11 is characterized in that the air gap between the second lens group and the third lens group is the largest in the air gap between the lenses.

  In a projection apparatus using a light valve such as a reflective liquid crystal or DMD, it is necessary to guide a light beam from a light source to a display element via an illumination optical system. At this time, it is necessary to bend the light flux from the illumination system by using a reflective optical element. For this reason, it is necessary to maximize the air gap between the second lens group and the third lens group. This makes it possible to insert a reflective optical element, and to guide the light beam from the illumination system to the display element.

  [13] A projection apparatus according to the present invention includes at least the projection lens according to any one of 1 to 12, an illumination optical system, and a display element.

  The projection device of the present invention has the effects described in 1 to 12.

  [14] The projector according to [13], wherein the lens closest to the display element in the projection lens is common to the lens closest to the display element in the illumination optical system.

  With this configuration, the projector can be further reduced in size.

  According to the projection lens of the present invention and the projection apparatus equipped with the projection lens, it can be miniaturized with a small number of lenses, has a bright and wide angle of view, and has a long reflective optical element insertion interval for inserting the reflective optical element. In addition, the telecentricity is excellent.

It is a block diagram of a projection apparatus. It is sectional drawing of a projection lens when the projection distance in Example 1 is 1020.50 mm. It is an aberration diagram when the projection distance in Example 1 is 1020.50 mm. FIG. 6 is an aberration diagram when the projection distance is 500.50 mm in Example 1. It is an aberration diagram when the projection distance in Example 1 is 160.50 mm.

FIG. 6 is a cross-sectional view of a projection lens when a projection distance is 1020.00 mm in Example 2. FIG. 6 is an aberration diagram when the projection distance is 1020.00 mm in Example 2. FIG. 6 is an aberration diagram when the projection distance is 500.00 mm in Example 2. It is an aberration diagram when the projection distance in Example 2 is 160.00 mm.

FIG. 10 is a cross-sectional view of the projection lens when the projection distance in Example 3 is 1020.00 mm. FIG. 6 is an aberration diagram when the projection distance is 1020.00 mm in Example 3. It is an aberration diagram when the projection distance in Example 3 is 500.00 mm. It is an aberration diagram when the projection distance in Example 3 is 160.00 mm.

FIG. 6 is a cross-sectional view of a projection lens when a projection distance is 1020.00 mm in Example 4. FIG. 9 is an aberration diagram when the projection distance is 1020.00 mm in Example 4. FIG. 6 is an aberration diagram when the projection distance is 500.00 mm in Example 4. FIG. 6 is an aberration diagram when the projection distance is 160.00 mm in Example 4.

10 is a cross-sectional view of a projection lens when a projection distance is 1020.00 mm in Example 5. FIG. FIG. 12 is an aberration diagram when the projection distance is 1020.00 mm in Example 5. FIG. 10 is an aberration diagram when the projection distance is 500.00 mm in Example 5. FIG. 10 is an aberration diagram when the projection distance is 160.00 mm in Example 5.

  An example of a projection apparatus provided with the projection lens of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of the projection apparatus.

  The projection apparatus mainly includes a projection lens 10, an illumination optical system 20, a light emitting unit 30, a reflecting mirror 40, a wire grid 50, a display element 60, and the like, and these members are held by a frame member 70.

  The projection lens 10 includes a first lens group L1, a second lens group L2, and a third lens group L3. Adjustment for focusing on the screen is performed by moving at least one of the first lens unit L1 and the second lens unit L2 in the optical axis direction.

  The actuator used for focusing includes an electromechanical conversion element, a drive friction member fixed to one end of the electromechanical conversion element in the expansion / contraction direction, and an engagement member that engages the drive friction member with a frictional force. A drive device that relatively drives the drive friction member and the engagement member by applying a voltage to the element to expand and contract may be used. A stepping motor or a voice coil motor may be used.

  The illumination optical system 20 includes a first lens 21, a second lens 22, a third lens 23, a fourth lens 24, and a fifth lens 25. In addition, it is not limited to such a lens structure, What kind of lens structure may be sufficient.

  The third lens unit L3 that is the lens closest to the display element 60 in the projection lens 10 is common to the fifth lens 25 that is the lens closest to the display element 60 in the illumination optical system 20.

  The light emitting unit 30 includes light emitting diodes (LEDs) of three colors of R (for example, wavelength 620 nm), G (for example, wavelength 530 nm), and B (for example, wavelength 460 nm). And when irradiating light, each color of R, G, B is emitted in a time-division manner, that is, each color is sequentially pulsed. The light emitting diodes are not limited to the three color light emitting diodes, and white light emitting diodes may be used.

  The reflecting mirror 40 reflects the light emitted from the light emitting unit 30 by changing the direction of the light by 90 degrees.

  The wire grid 50 is a beam splitter having a function of reflecting light in a predetermined vibration direction. In this example, the light transmitted through the first lens 21 to the fourth lens 24 is transmitted and guided to the display element 60, thereby displaying the display element. The light whose polarization state is changed by the reflection at 60 is reflected. Instead of the wire grid, two rectangular prisms may be joined and a thin film may be applied to the joining surface.

  The display element 60 is a reflective liquid crystal panel in which a liquid crystal is formed on a silicon substrate, forms an image pattern of an image to be projected, and is also referred to as LCOS (Liquid Crystal On Silicon). The display element is not limited to a liquid crystal panel as long as it is a reflection type, and for example, a DMD may be used.

  Further, a cover glass CG is located in front of the display element 60.

  Thus, the display element 60 is illuminated by the light emitted from the light emitting unit 30 via the illumination optical system 20, the reflecting mirror 40, and the wire grid 50, and the image of the display element 60 surface whose polarization state is controlled for each pixel is a wire. After being reflected by the grid 50, the projection lens 10 magnifies and projects it onto the screen.

  In this projection apparatus, since the projection lens according to the present invention is used, a long reflective optical element insertion interval is ensured, the telecentricity is excellent, and a bright and wide angle of view can be obtained. Further, by using a lens common to the illumination optical system, it is possible to reduce the size of the apparatus with a small number of lenses.

  Examples of the projection lens of the present invention are shown below. Symbols used in each example are as follows.

R: Radius of curvature D: Axis upper surface distance Nd: Refractive index of lens material with respect to d-line νd: Abbe number of lens material d: Projection distance f: Focal length of entire projection lens system F: F number L: Projection lens at each position Overall length of the entire system fB: Back focus 2Y: Image height 2ω: Field angle In each embodiment, the surface where “*” is written after each surface number is an aspheric surface. The shape is expressed by the following formula 1, where the vertex of the surface is the origin, the X axis is taken in the optical axis direction, and the height in the direction perpendicular to the optical axis is h.

However,
Ai: i-order aspherical coefficient R: radius of curvature K: conic constant In the aspherical coefficient, a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02). .
[Example 1]
・ Lens surface data is shown below.

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
Projection distance ∞ d
1 9.197 0.50 1.63630 58.5 3.49
2 3.333 1.30 2.76
3 7.553 1.50 1.84670 24.0 2.71
4 -26.199 0.60 1.48750 70.2 2.48
5 3.580 1.50 2.00
6 (Aperture) ∞ 1.00 1.80
7 -7.008 0.50 1.63200 23.0 2.07
8 5.946 1.95 1.72920 54.7 2.56
9 -4.724 0.50 2.71
10 (*) 4.536 1.50 1.49 140 59.9 2.80
11 (*) 29.720 d1 2.76
12 (*) 5.897 1.46 1.49 140 59.9 2.51
13 (*) -15.526 1.10 2.51
14 ∞ 0.70 1.51680 64.2 2.44
15 ∞ 2.42
Display element ∞
・ Aspheric coefficient is shown below.
10th page
K = 0.00000E + 00, A4 = -0.31700E-03, A6 = -0.56658E-04, A8 = 0.12099E-04, A10 = -0.15697E-05
11th page
K = 0.00000E + 00, A4 = 0.47867E-03, A6 = -0.17823E-04, A8 = 0.61946E-05, A10 = -0.13578E-05
12th page
K = 0.00000E + 00, A4 = -0.63824E-02, A6 = 0.20526E-02, A8 = -0.50803E-03, A10 = 0.28469E-04
Side 13
K = 0.00000E + 00, A4 = 0.33883E-02, A6 = 0.14882E-02, A8 = -0.38110E-03, A10 = 0.86410E-06, A12 = 0.27470E-05
・ Various data corresponding to the projection distance are shown below.

d f F d1 L fB 2Y 2ω
1020.50 3.60 1.33 4.0116 18.63 1.56 4.8 68.7
500.50 3.60 1.33 4.0107 18.63 1.56 4.8 68.7
160.50 3.63 1.34 4.1000 18.72 1.56 4.8 68.2
-Values corresponding to the above conditional expressions are shown below.
f1 / f2 = −1.56
f1a / f = −2.36
d12 / f = 0.52
nd1b1-nd1b2 = 0.36
νd1b1−νd1b2 = −46.2
f3 / f = 2.47
FIG. 2 is a cross-sectional view of the projection lens when the projection distance is 1020.50 mm. The projection lens includes, in order from the projection surface side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens L3 group having a positive refractive power. The first lens unit L1 includes one lens 1a and a lens unit 1b having negative refractive power from the projection surface side, and the lens group 1b includes one positive lens and one negative lens from the projection surface side. Consists of. Then, the first lens unit L1 and the second lens unit L2 are moved in the optical axis direction according to the projection distance.

3 is an aberration diagram when the projection distance is 1020.50 mm, FIG. 4 is an aberration diagram when the projection distance is 500.50 mm, and FIG. 5 is an aberration diagram when the projection distance is 160.50 mm.
[Example 2]
・ Lens surface data is shown below.

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
Projection distance ∞ d
1 15.154 0.40 1.72920 54.7 3.05
2 2.987 1.03 2.39
3 6.868 1.02 1.92290 20.9 2.37
4 -43.779 0.50 1.48750 70.2 2.25
5 (*) 2.839 2.59 1.90
6 (Aperture) ∞ 0.50 1.88
7 -19.294 0.40 1.92290 20.9 2.01
8 6.010 1.29 1.88300 40.8 2.21
9 -11.323 0.20 2.36
10 (*) 13.423 1.38 1.72920 54.7 2.53
11 (*) -5.652 d1 2.54
12 (*) 4.832 1.00 1.72920 54.7 2.45
13 (*) 267.288 0.70 2.39
14 ∞ 0.70 1.51680 64.2 2.50
15 ∞ 2.50
Display element ∞
・ Aspheric coefficient is shown below.
5th page
K = 0.00000E + 00, A4 = -0.24246E-02, A6 = 0.14793E-03, A8 = -0.14573E-03, A10 = -0.64116E-05
10th page
K = 0.00000E + 00, A4 = -0.95967E-04, A6 = 0.18961E-04, A8 = -0.59021E-05, A10 = 0.26080E-05
11th page
K = 0.00000E + 00, A4 = 0.98542E-03, A6 = 0.50290E-04, A8 = -0.19853E-04, A10 = 0.38892E-05
12th page
K = 0.00000E + 00, A4 = 0.53852E-02, A6 = -0.12312E-02
Side 13
K = 0.00000E + 00, A4 = 0.18783E-01, A6 = -0.37046E-02, A8 = 0.22129E-03
・ Various data corresponding to the projection distance are shown below.

d f F d1 L fB 2Y 2ω
1020.00 2.90 1.47 6.5868 18.30 1.16 4.8 79.4
500.00 2.90 1.47 6.6011 18.31 1.16 4.8 79.3
160.00 2.92 1.48 6.6573 18.37 1.16 4.8 79.3
-Values corresponding to the above conditional expressions are shown below.
f1 / f2 = −0.91
f1a / f = −1.79
d12 / f = 0.79
nd1b1-nd1b2 = 0.44
νd1b1−νd1b2 = −49.4
f3 / f = 2.33
FIG. 6 is a sectional view of the projection lens when the projection distance is 1020.00 mm. The projection lens includes, in order from the projection surface side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens L3 group having a positive refractive power. The first lens unit L1 includes one lens 1a and a lens unit 1b having negative refractive power from the projection surface side, and the lens group 1b includes one positive lens and one negative lens from the projection surface side. Consists of. Then, the first lens unit L1 and the second lens unit L2 are moved in the optical axis direction according to the projection distance.

7 is an aberration diagram when the projection distance is 1020.00 mm, FIG. 8 is an aberration diagram when the projection distance is 500.00 mm, and FIG. 9 is an aberration diagram when the projection distance is 160.00 mm.
[Example 3]
・ Lens surface data is shown below.

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
Projection distance ∞ d
1 -99.881 0.36 1.72920 54.7 2.44
2 2.784 0.78 2.02
3 6.310 1.38 1.92290 20.9 2.05
4 -9.417 0.36 1.70610 55.5 1.97
5 (*) 8.572 d1 1.87
6 (Aperture) ∞ 0.40 1.65
7 -6.539 0.60 1.89720 21.3 1.69
8 4.995 2.00 1.86040 42.1 1.97
9 -6.030 0.20 2.26
10 (*) 9.808 1.30 1.74780 52.2 2.39
11 (*) -10.423 7.20 2.40
12 (*) 5.000 1.00 1.72920 54.7 2.38
13 (*) 17.818 0.70 2.30
14 ∞ 0.70 1.51680 64.2 2.50
15 ∞ 2.50
Display element ∞
・ Aspheric coefficient is shown below.
5th page
K = 0.00000E + 00, A4 = -0.17807E-02, A6 = -0.38685E-04, A8 = -0.88163E-04, A10 = 0.10227E-05
10th page
K = 0.00000E + 00, A4 = -0.52484E-03, A6 = -0.14315E-03, A8 = 0.22988E-04, A10 = -0.37415E-05
11th page
K = 0.00000E + 00, A4 = -0.12296E-03, A6 = -0.14308E-03, A8 = 0.20799E-04, A10 = -0.31675E-05
12th page
K = 0.00000E + 00, A4 = -0.28346E-03, A6 = -0.51047E-03
Side 13
K = 0.00000E + 00, A4 = 0.33049E-02, A6 = -0.12674E-02, A8 = 0.11981E-03
・ Various data corresponding to the projection distance are shown below.

d f F d1 L fB 2Y 2ω
1020.00 3.50 1.68 1.4648 18.44 1.16 4.8 68.9
500.00 3.49 1.68 1.4948 18.47 1.16 4.8 69.0
160.00 3.45 1.69 1.6209 18.60 1.16 4.8 69.9
-Values corresponding to the above conditional expressions are shown below.
f1 / f2 = −1.16
f1a / f = −1.06
d12 / f = 0.42
nd1b1-nd1b2 = 0.22
νd1b1−νd1b2 = −34.7
f3 / f = 2.63
FIG. 10 is a sectional view of the projection lens when the projection distance is 1020.00 mm. The projection lens includes, in order from the projection surface side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens L3 group having a positive refractive power. The first lens unit L1 includes one lens 1a and a lens unit 1b having negative refractive power from the projection surface side, and the lens group 1b includes one positive lens and one negative lens from the projection surface side. Consists of. Then, the first lens unit L1 is moved in the optical axis direction according to the projection distance.

11 is an aberration diagram when the projection distance is 1020.00 mm, FIG. 12 is an aberration diagram when the projection distance is 500.00 mm, and FIG. 13 is an aberration diagram when the projection distance is 160.00 mm.
[Example 4]
・ Lens surface data is shown below.

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
Projection distance ∞ d
1 1476.353 0.40 1.72920 54.7 2.48
2 2.877 0.88 2.05
3 7.797 1.33 1.92290 20.9 2.07
4 -8.506 0.40 1.48750 70.2 1.99
5 (*) 4.799 1.44 1.80
6 (Aperture) ∞ 0.42 1.66
7 -7.902 0.50 1.92290 20.9 1.71
8 4.985 1.85 1.88300 40.8 1.96
9 -7.196 0.20 2.23
10 (*) 16.461 1.50 1.72920 54.7 2.35
11 (*) -6.130 d1 2.51
12 (*) 5.558 1.00 1.72920 54.7 2.45
13 (*) 40.031 0.70 2.34
14 ∞ 0.70 1.51680 64.2 2.50
15 ∞ 2.50
Display element ∞
・ Aspheric coefficient is shown below.
5th page
K = 0.00000E + 00, A4 = -0.76606E-04, A6 = 0.18454E-03, A8 = -0.14730E-03, A10 = 0.39815E-05
10th page
K = 0.00000E + 00, A4 = -0.50923E-03, A6 = -0.57620E-04, A8 = 0.87942E-05, A10 = -0.17218E-05
11th page
K = 0.00000E + 00, A4 = 0.21875E-03, A6 = -0.84140E-04, A8 = 0.14007E-04, A10 = -0.17991E-05
12th page
K = 0.00000E + 00, A4 = 0.19353E-02, A6 = -0.29871E-03
Side 13
K = 0.00000E + 00, A4 = 0.77051E-02, A6 = -0.11414E-02, A8 = 0.71259E-04
・ Various data corresponding to the projection distance are shown below.

d f F d1 L fB 2Y 2ω
1020.00 3.47 1.69 7.2000 18.51 1.16 4.8 69.4
500.00 3.48 1.69 7.2175 18.53 1.16 4.8 69.3
160.00 3.50 1.70 7.2900 18.60 1.16 4.8 69.2
-Values corresponding to the above conditional expressions are shown below.
f1 / f2 = −1.13
f1a / f = −1.14
d12 / f = 0.42
nd1b1-nd1b2 = 0.44
νd1b1−νd1b2 = −49.4
f3 / f = 2.52
FIG. 14 is a sectional view of the projection lens when the projection distance is 1020.00 mm. The projection lens includes, in order from the projection surface side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens L3 group having a positive refractive power. The first lens unit L1 includes one lens 1a and a lens unit 1b having negative refractive power from the projection surface side, and the lens group 1b includes one positive lens and one negative lens from the projection surface side. Consists of. Then, the first lens unit L1 and the second lens unit L2 are moved in the optical axis direction according to the projection distance.

15 is an aberration diagram when the projection distance is 1020.00 mm, FIG. 16 is an aberration diagram when the projection distance is 500.00 mm, and FIG. 17 is an aberration diagram when the projection distance is 160.00 mm.
[Example 5]
・ Lens surface data is shown below.

Surface number R (mm) D (mm) Nd νd Effective radius (mm)
Projection distance ∞ d
1 -16.269 0.40 1.72920 54.7 2.46
2 2.960 1.23 2.07
3 31.159 1.26 1.92290 20.9 2.18
4 -5.832 0.40 1.49710 81.6 2.24
5 (*) -93.457 d1 2.23
6 (Aperture) ∞ 0.41 1.91
7 -10.162 0.40 1.92290 20.9 1.94
8 5.792 1.96 1.80420 46.5 2.11
9 -5.880 0.20 2.35
10 (*) 11.088 1.08 1.80139 45.4 2.40
11 (*) -22.475 d2 2.49
12 (*) 5.070 1.00 1.72903 54.0 2.43
13 (*) 77.844 0.70 2.36
14 ∞ 0.70 1.51680 64.2 2.27
15 ∞ 2.21
Display element ∞
・ Aspheric coefficient is shown below.
5th page
K = 0.00000E + 00, A4 = -0.22278E-02, A6 = -0.14378E-03, A8 = -0.27421E-04, A10 = -0.15531E-05
10th page
K = 0.00000E + 00, A4 = -0.66418E-03, A6 = -0.20829E-03, A8 = 0.19746E-04, A10 = -0.39054E-05
11th page
K = 0.00000E + 00, A4 = -0.77078E-03, A6 = -0.19606E-03, A8 = 0.12076E-04, A10 = -0.25913E-05
12th page
K = 0.00000E + 00, A4 = 0.13837E-02, A6 = 0.19267E-03, A8 = -0.13043E-03, A10 = 0.22081E-05
Side 13
K = 0.00000E + 00A4 = 0.96672E-02, A6 = -0.17038E-03, A8 = -0.28269E-03, A10 = 0.21431E-04
・ Various data corresponding to the projection distance are shown below.

d f F d1 d2 L fB 2Y 2ω
1020.00 3.34 1.68 2.1642 7.697 19.60 1.16 4.8 71.5
500.00 3.36 1.69 2.1335 7.728 19.60 1.16 4.8 71.3
160.00 3.43 1.71 1.9997 7.862 19.60 1.16 4.8 70.3
-Values corresponding to the above conditional expressions are shown below.
f1 / f2 = −1.23
f1a / f = -1.02
d12 / f = 0.59
nd1b1-nd1b2 = 0.43
νd1b1−νd1b2 = −60.7
f3 / f = 2.22
FIG. 18 is a sectional view of the projection lens when the projection distance is 1020.00 mm. The projection lens includes, in order from the projection surface side, a first lens unit L1 having a negative refractive power, a second lens unit L2 having a positive refractive power, and a third lens L3 group having a positive refractive power. The first lens unit L1 includes one lens 1a and a lens unit 1b having negative refractive power from the projection surface side, and the lens group 1b includes one positive lens and one negative lens from the projection surface side. Consists of. Then, the second lens unit L2 is moved in the optical axis direction according to the projection distance.

  19 is an aberration diagram when the projection distance is 1020.00 mm, FIG. 20 is an aberration diagram when the projection distance is 500.00 mm, and FIG. 21 is an aberration diagram when the projection distance is 160.00 mm.

  In each of the above embodiments, the lens system is further reduced in size by generating a relatively large negative distortion. At this time, it is desirable to perform electronic distortion correction in order to maintain the quality of the projected image.

L1 First lens group L2 Second lens group L3 Third lens group 1a Lens 1b Lens group

Claims (14)

In order from the projection surface side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, and the first lens group includes: 1a lens and 1b lens group having one negative refractive power from the projection surface side, and the 1b lens group is composed of one positive lens and one negative lens from the projection surface side. A projection lens characterized by satisfying
−2.0 <f ₁ / f ₂ <−0.7
However,
f ₁ : Composite focal length of the first lens group f ₂ : Composite focal length of the second lens group The projection lens according to claim 1, wherein the following conditional expression is satisfied.
−2.5 <f _1a /f<−1.0
However,
f _1a : focal length of the 1a lens f: focal length of the entire system The projection lens according to claim 1, wherein the following conditional expression is satisfied.
0.4 <d ₁₂ / f ₁₂ <0.8
However,
d ₁₂ : Air distance between the first lens group and the second lens group f ₁₂ : Composite focal length of the first lens group and the second lens group   The second lens group has an aperture stop on the most projection surface side, and has at least one negative lens and one positive lens in order from the projection surface side. The projection lens according to Item 1. The projection lens according to claim 1, wherein the positive lens and the negative lens of the 1b lens group are cemented with each other and satisfy the following conditional expression.
0.2 <n _d1b1 -n _d1b2
−65 <ν _d1b1 −ν _d1b2 <−30
However,
_n d1b1: the 1b lens group having a positive lens having a refractive index _n d1b2: the refractive index of the negative lens of the 1b lens group _ν d1b1: the 1b lens group having a positive lens Abbe number _ν d1b2: the negative lens of the 1b lens group Abbe number The projection lens according to claim 1, wherein the following conditional expression is satisfied.
2.0 <f ₃ /f<3.0
However,
f ₃ : focal length of the third lens group   The projection lens according to claim 1, wherein focusing is performed by moving the first lens group in an optical axis direction.   The projection lens according to claim 1, wherein focusing is performed by moving the second lens group in an optical axis direction.   The projection lens according to claim 1, wherein focusing is performed by moving the first lens group and the second lens group in an optical axis direction.   The projection lens according to claim 1, wherein the 1b lens group has a positive refractive power.   The projection lens according to claim 1, wherein the third lens group includes one positive lens.   12. The projection lens according to claim 1, wherein an air space between the second lens group and the third lens group is a maximum in an air space between the lenses.   A projection apparatus comprising at least the projection lens according to claim 1, an illumination optical system, and a display element.   The projection apparatus according to claim 13, wherein a lens closest to the display element in the projection lens is common to a lens closest to the display element in the illumination optical system.

Images