JP2016031403A - Illumination optical system and projection display device with illumination optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve light utilization efficiency with a small-sized configuration.SOLUTION: An illumination optical system 20A illuminating a liquid crystal panel 40 modulating light from a light source unit 10 with the light, includes, in order from a light source side along an optical path, a first lens array 22 and a second lens array 24 splitting a bundle of light rays to a plurality of bundles of light rays, and a condenser lens system. The condenser lens system includes in order from the light source side along the optical path: a first lens system 26A acting to condense a bundle of light rays and having a positive refraction factor; and a second lens group 27A acting not only to condense a bundle of light rays but also to correct chromatic aberration under a predetermined condition and having a positive refraction factor in order from the light source side along the optical path. The first lens group 26A is constituted by a single lens, and the second lens group 27A includes one positive lens 28A and one negative lens 29A in order from the light source side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an illumination optical system that illuminates a light modulation element such as a liquid crystal panel, and a projection display device having the illumination optical system.

  Projection-type display devices such as liquid crystal projectors in recent years are required to have higher light utilization efficiency and further miniaturization. Therefore, Patent Document 1 proposes a polarization illumination device that separates polarized light at a stage where an integrator optical system and a polarization conversion optical system are combined and a minute secondary light source image is generated by the integrator optical system.

JP-A-8-304739

  The conventional illumination optical system forms an excessive illumination range and absorbs illumination light outside the illumination margin range in order to absorb the deviation of the illumination range due to aberration. Since the light use efficiency decreases due to the loss of illumination light, it is necessary to keep the illuminance outside the illumination margin range low. The effective illumination range is the common part of the illumination ranges of all wavelengths inside the illumination margin range, and this is set as the range of the liquid crystal panel. In the configuration of Patent Document 1, a large amount of chromatic aberration (particularly lateral chromatic aberration) occurs in the condensing lens system, the illuminance outside the illumination margin range is high, and the light utilization efficiency is low. Further, there is a demand for further miniaturization of the illumination optical system.

  An object of the present invention is to provide an illumination optical system capable of improving light utilization efficiency with a small configuration, and a projection display device having the illumination optical system.

An illumination optical system according to the present invention is an illumination optical system that illuminates a light modulation element that modulates light from a light source with the light, and sequentially converts a light beam from the light source into a plurality of light beams along an optical path from the light source side. A splitting unit for splitting, and a condensing lens system, and the condensing lens system has an action of condensing the light beams split by the splitting unit in order along the optical path from the light source side. A first lens group having a positive refractive index and a second lens group having a positive refractive index, wherein the first lens group is constituted by a single lens, and the second lens group is arranged on the light source side. To the optical path in order, one positive lens and one negative lens. The second lens group has a total focal length of the condenser lens system as Fall, The focal length of the lens unit is f1, the Abbe number of the first lens unit is ν1, and the front The focal length of the positive lens of the second lens group is f2p, the focal length of the positive lens of the second lens group is ν2p, the focal length of the negative lens of the second lens group is f2n, and the focal length of the second lens group When the focal length of the positive lens is ν2n, in addition to the above action,
It has the effect | action which corrects the chromatic aberration which satisfy | fills.

  ADVANTAGE OF THE INVENTION According to this invention, the illumination optical system which can improve light utilization efficiency with a small structure, and a projection type display apparatus having the same can be provided.

It is sectional drawing from the light source of the liquid crystal projector of this invention to a liquid crystal panel. Example 1 It is a graph showing the illumination distribution of the illumination range end part of the illumination optical system shown in FIG. Example 1 It is sectional drawing from the light source of the liquid crystal projector of this invention to a liquid crystal panel. (Example 2) It is a graph showing the illumination distribution of the illumination range edge part of the illumination optical system shown in FIG. (Example 2) It is sectional drawing from the light source of the liquid crystal projector of a comparative example to a liquid crystal panel. It is a graph showing the illumination distribution of the illumination range end part of the illumination optical system shown in FIG.

  The present embodiment relates to an illumination optical system and a liquid crystal projector having the illumination optical system. A liquid crystal projector is an example of a projection display device (image display device), modulates light from a light source according to a video signal, and projects the light onto a projection surface such as a screen. The liquid crystal projector includes a light source, an illumination optical system, a liquid crystal panel, a synthesis optical system, and a projection optical system.

  FIG. 1 is a cross-sectional view from the light source to the liquid crystal panel of the liquid crystal projector of the first embodiment. The liquid crystal projector shown in FIG. 1 includes a light source unit 10, an illumination optical system 20A, and a liquid crystal panel 40.

  The light source unit 10 includes a light source such as an unillustrated extra-high pressure mercury lamp or xenon lamp, and a reflector that reflects light from the light source.

  The illumination optical system 20 </ b> A is an optical system that illuminates the liquid crystal panel 40 using light from the light source unit 10. The illumination optical system 20A includes, in order along the optical path from the light source side, a concave lens 21, a first lens array 22, a UV cut filter 23, a second lens array 24, a polarization conversion element 25, a condensing lens system, and a polarization beam splitter 30. Have.

  The concave lens 21 converts light emitted from the light source unit 10 into substantially parallel light. Between the light source unit 10 and the concave lens 21, there may be provided a color separation means for splitting light from the light source into a plurality of color lights. The color separation means may be composed of, for example, two dichroic mirrors.

  For example, light from the light source unit is incident on a first dichroic mirror, and the first dichroic mirror reflects green (hereinafter referred to as “G”) component light, and red (hereinafter referred to as “R”). And component light of blue (hereinafter referred to as “B”) are transmitted. G component light, R component light, and B component light have different wavelength regions. As a result, the G component light and the RB component light are separated. Next, the component light of RB enters the second dichroic mirror. The second dichroic mirror reflects R component light and transmits B component light. As a result, the R component light and the B component light are separated. The optical path of the component light of G may be bent by a bending mirror or the like.

  The first lens array 22 and the second lens array 24 constitute a splitting unit that splits the light beam from the light source into a plurality of light beams.

  The first lens array 22 is an integrator in which rectangular lens cells are two-dimensionally arranged to divide incident light into a plurality of lights.

  The UV cut filter 23 removes ultraviolet light from the light from the light source unit 10. If necessary, a UV-IR (ultraviolet / infrared light) cut filter that further removes infrared light may be used.

  The second lens array 24 also has a configuration in which rectangular lens cells are two-dimensionally arranged. The light transmitted through the first lens array 22 and divided is temporarily condensed by the lens cell of the corresponding second lens array 24.

  The polarization conversion element 25 aligns the polarization direction of incident light. By the polarization conversion element 25, the polarization state of the incident light is aligned from the non-polarization state to the polarization direction that is transmitted through the polarization beam splitter 30.

  The condensing lens system condenses incident light and has a two-group configuration including a first lens group 26A and a second lens group 27A in order along the optical path from the light source side. The first lens group 26A has a function of condensing the light beam divided by the dividing unit and has a positive refractive index. The second lens group 27A has a function of correcting chromatic aberration in addition to the above function, and has a positive refractive index. Since a bending mirror (not shown) that bends the optical path is disposed between the polarization conversion element 25 and the first lens group 26A, the interval is slightly widened, but this is not an essential configuration. The first lens group 26A is composed of a single lens.

  The second lens group 27A has a bonded lens configuration of a two-group lens of a positive lens 28A and a negative lens 29A along the optical path from the light source side. Both the first lens group 26A and the second lens group 27A have positive refractive power. Here, the focal length of the first lens group 26A is f1, the Abbe number is ν1, the combined focal length of the second lens group 27A is f2, the focal length of the positive lens 28A of the second lens group is f2p, and the Abbe number is It is assumed that ν2p, the focal length of the positive lens 29A of the second lens group is f2n, and the Abbe number is ν2n. Further, the focal length of the entire condenser lens system is Fall, the distance between the first lens group 26A and the second lens group 27A is D12, and the following conditional expressions (1), (2), (3), ( Satisfying 4) is preferable for aberration correction.

  Each term on the left side of the conditional expression (1) is a parameter indicating the degree of chromatic aberration of the single lens constituting each group, and the entire left side indicates the degree of chromatic aberration of the entire lens system. By taking the first term indicating the chromatic aberration parameter of the first lens group and the chromatic aberration parameter of the second lens group (second term + third term) so as to have opposite signs and the absolute values being substantially equal, This represents a reduction in the overall chromatic aberration.

  Conditional expression (2) represents the ratio of the focal length of the first lens group 26A to the focal length of the entire system. If this ratio exceeds the lower limit, the positive refractive power of the first lens group 26A increases, so that the correction of spherical aberration increases, and even if correction is performed with only one negative lens 29A, sufficient correction cannot be performed. . Further, if this ratio exceeds the upper limit value, the focal length becomes longer, and the entire lens system becomes larger. Conditional expression (2) may be replaced by the following expression.

  Conditional expression (3) represents the ratio of the focal length of the second lens group 27A to the focal length of the entire system. When this ratio exceeds the lower limit value, the positive refractive power of the second lens group 27A increases, so that the correction of spherical aberration increases, and even if correction is performed with one negative lens, sufficient correction cannot be performed. Further, if this ratio exceeds the upper limit value, the focal length becomes longer, and the entire lens system becomes larger. Conditional expression (3) may be replaced by the following expression.

  Conditional expression (4) represents the ratio between the distance between the first lens group 26A and the second lens group 27A and the focal length of the entire system. If this ratio exceeds the lower limit, the first lens group 26A and the second lens group 27A are too close together, but the focal length of the entire system is fixed, so the principal point position moves to the image side, and the entire system is large. It will become. When this ratio exceeds the upper limit value, the distance from the second lens group 27A to the liquid crystal panel 40 becomes small. The liquid crystal panel 40 of the present embodiment is of a reflective type, and if the space for arranging the polarization beam splitter 30 for making the modulated light incident on the projection lens side is secured, the refractive power of the second lens group 27A becomes large, Aberration increases. Conditional expression (3) may be replaced by the following expression.

  The second lens group 27A includes, in order from the light source side, a positive lens 28A as a biconvex lens having a positive refractive index and a negative lens 29A as a biconcave lens having a negative refractive index. Therefore, it can be reduced in size.

  As a condition for effectively performing the achromatization, when the Abbe number of the glass material of the first lens group 26A, which is a positive lens, is ν1p, and the Abbe number of the glass material of the positive lens 28A of the second lens group 27A is ν2p, Is preferably satisfied.

60 <ν1p <70 (5)
50 <ν2p <70 (6)
If the lower limit value of conditional expressions (5) and (6) is exceeded, it will be difficult to achromatic the second lens group 27A. If the upper limit values of conditional expressions (5) and (6) are exceeded, it becomes difficult to select the glass material.

  Conditional expressions (5) and (6) may be replaced by the following expressions.

60 <ν1p <65 (5) ′
55 <ν2p <65 (6) ′
Further, as a condition for achromaticity in the second lens group 27A, if the Abbe number of the glass material constituting the positive lens 28A of the second lens group 27A is ν2p and the Abbe number of the material constituting the negative lens 29A is ν2n. By satisfying the following expression, chromatic aberration can be corrected effectively.

20 ≦ ν2p−ν2n ≦ 40 (7)
Conditional expression (7) may be replaced by the following expression.

25 ≦ ν2p−ν2n ≦ 35 (7) ′
The light (GRB component light) that has passed through the condenser lens system is incident on the polarization beam splitter 30 corresponding to each color light. The polarization beam splitter 30 functions as polarization separation means having a polarization separation surface that transmits the first polarized light and reflects the second polarized light. The polarization directions of the first polarization and the second polarization are orthogonal to each other. For example, the first polarization is P polarization and the second polarization is S polarization.

  Each component light of GRB reflected by the polarization beam splitter 30 is supplied to a reflective liquid crystal panel 40 corresponding to each color light. The light beam divided by the polarization conversion element 25 is superposed on the liquid crystal panel 40 so as to become an image side telecentric optical system by a condensing lens system. The liquid crystal panel 40 is a light modulation element that modulates and reflects each component light in accordance with a video signal output from a video signal output unit described later.

  The GBR component lights reflected by the liquid crystal panel 40 and converted in polarization direction are returned to the polarization beam splitter 30 again. As a result, the component light of the GBR is transmitted through the polarization beam splitter 30 and incident on a composite optical system (not shown) (for example, an X prism) and the component light component reflected by the polarization beam splitter 30 and returning to the light source direction. And separated. The synthesizing optical system has a function of synthesizing component lights that have passed through the polarization beam splitter 30, and supplies the synthesized light to a projection lens (projection optical system) (not shown). The projection lens has a zoom function, projects the supplied combined light onto a projection surface such as a screen at an arbitrary magnification, and displays an image. For example, the combining optical system, the projection lens, and the projection surface are disposed above the polarizing beam splitter 30 in FIG. Although an example in which three liquid crystal panels are used has been described, the present invention is not limited to this, and color reproduction may be performed by time division using a single liquid crystal panel.

(Numerical example 1)
Table 1 shows the conditional expressions and numerical values of Numerical Example 1 in the configuration shown in FIG. As shown in Table 1, f1 / Fall = 2.2, f2 / Fall = 1.7, D12 / Fall = 0.15, ν1p = 61.2, ν2p = 60.3, ν2p−ν2n = 32.8 It is.

Further, Ri is the i-th radius of curvature in order from the first surface of the condenser lens system from the object side, Di is the i-th and i + 1-th intervals in order from the object side, and Ni and νi are respectively in order from the object side. Assuming that the refractive power and Abbe number of the material of the i-th optical material are given, Numerical Example 1 is as follows.
R1 = 99.043 D1 = 3.0 N1 = 1.5891 ν1 = 61.2
R2 = -798.546 D2 = 10.7
R3 = 44.371 D3 = 7.5 N2 = 1.6206 ν2 = 60.3
R4 = −107.607 D4 = 2.0 N3 = 1.7553 ν3 = 27.5
R5 = 161.817 D5 = 54.7

(Comparative example)
FIG. 5 is a cross-sectional view from a light source to a liquid crystal panel of a liquid crystal projector as a comparative example. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals. The condensing lens system of the comparative example condenses incident light and has a two-group configuration including a first lens group 26C and a second lens group 27C. The first lens group 26C is a plano-convex lens having a flat light source side, and is a single lens having positive refractive power. The second lens group 27C is a biconvex lens and is a single lens having a positive refractive power. In the comparative example, since a folding mirror (not shown) that bends the optical path is disposed in the condensing lens system, the distance between the first lens group 26C and the second lens group 27C is slightly increased. In the configuration shown in FIG. 5, it is necessary to ensure a long back focus of the condensing lens system. If an attempt is made to suppress an increase in the size of the entire optical system, the power of the second lens group 27C increases, and spherical aberration and the like occur. It becomes easy. In the comparative example, none of the conditional expressions (1) to (7) is satisfied.

  2 is a cross-sectional view of the illuminance distribution at the end of the illumination range in the configuration of Example 1, and FIG. 6 is a cross-sectional view of the illuminance distribution at the end of the illumination range in the configuration of the comparative example. Hereinafter, the effects of the first embodiment will be described with reference to FIGS.

  The “liquid crystal panel cross-sectional coordinate (mm)” on the horizontal axis in FIGS. 2 and 6 represents the length from the optical axis (center) of the liquid crystal panel 40 in FIGS. 1 and 5 to the downward direction. There is an illumination margin boundary line A at a position of −5.0 mm on the horizontal axis, and a panel boundary line B is positioned at a position of −4.8 mm. 2 and 6, the right side is omitted from −4.7 mm, but there is a panel boundary B at +4.8 mm, and there is an illumination margin boundary A at +5.0 mm, and each panel boundary B Each illumination margin boundary line A extends in a direction perpendicular to the paper surface of FIG. Note that there are illumination margin boundary lines and panel boundary lines in the direction parallel to the paper surface of FIG. 1 as well, and the following description applies to these as well.

  The liquid crystal panel 40 is configured such that photoelectric conversion elements such as photodiodes arranged in the range of −4.8 mm to +4.8 mm can perform photoelectric conversion. Further, the illumination margin boundary line A is a range where the illumination light hits due to chromatic aberration even in a range exceeding the panel boundary line B. And the light outside the illumination margin boundary A is not used as useless illumination light. The “illuminance” on the vertical axis indicates the ratio (%) normalized by the illuminance at the 0 mm position of the liquid crystal panel 40 on the horizontal axis.

  The ideal illumination distribution has an illuminance of 0% outside the illumination range (ie, to the left of the illumination margin boundary A shown in FIGS. 2 and 6), rises at the illumination margin boundary A, and is within the illumination range (ie, On the right side of the illumination margin boundary line A shown in FIGS. 2 and 6, the illuminance of about 100% is maintained. In addition, each color light of RGB rises to about 100% when the illumination margin boundary A rises.

  In FIG. 6, the light loss on the left side of the illumination margin boundary A is larger, and the illuminance of the B light at the illumination margin boundary A is lower than the G light and R light. On the other hand, in FIG. 2, light loss on the left side of the illumination margin boundary A is reduced by improving spherical aberration and the like as compared with FIG. Has been. Thus, Example 1 can improve illumination efficiency and color reproducibility compared with a comparative example.

  Hereinafter, the improvement effect of the condensing lens system by the illumination optical system 20B of Example 2 will be described with reference to FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals. The second embodiment is different from the first embodiment in the configuration of the condenser lens system.

  In Example 2, the condensing lens system condenses incident light, satisfies the above-described conditions of refractive power arrangement and color dispersion, and has a two-group configuration including a first lens group 26B and a second lens group 27B. ing. The first lens group 26B is composed of a single lens. The second lens group 27B has a two-group lens configuration in which the positive lens 28B and the negative lens 29B are arranged in this order from the light source side, but is not bonded, and there is a gap between the positive lens 28B and the negative lens 29B (both Are far away). By separating the positive lens 28B and the negative lens 29B, the refractive power of the first lens group 26B becomes strong, and a convex meniscus lens having a positive refractive power and a convex surface on the display element side is obtained.

The distance S on the optical axis between the negative lens side surface of the positive lens 28B and the positive lens side surface of the negative lens 29B preferably satisfies the following conditional expression. In the formula (8), when S is smaller than the lower limit value, the effect of improving the shift due to the wavelength at the end of the illuminance distribution is reduced. When S is larger than the upper limit value, spherical aberration at the illumination margin boundary of the illuminance distribution becomes large, color reproducibility is lowered, and the illumination optical system becomes large.
0.00147 <S / Fall <0.147 (8)
Conditional expression (8) may be replaced by the following expression.
0.0147 <S / Fall <0.0736 (8) '

(Numerical example 2)
Table 1 shows the conditional expressions and numerical values of Numerical Example 2 in the configuration shown in FIG. As shown in Table 1, f1 / Fall = 2.4, f2 / Fall = 1.7, D12 / Fall = 0.1, S / Fall = 0.035, ν1p = 62.1, ν2p = 59.7 , Ν2p−ν2n = 31.8.

Further, Ri is the i-th radius of curvature in order from the first surface of the condenser lens system from the object side, Di is the i-th and i + 1-th intervals in order from the object side, and Ni and νi are respectively in order from the object side. Assuming that the refractive power and the Abbe number of the i-th optical material are used, Numerical Example 2 is as follows.
R1 = −51.214 D1 = 2.57 N1 = 1.5814 ν1 = 62.1
R2 = -33.993 D2 = 6.35
R3 = 35.639 D3 = 5.98 N2 = 1.6234 ν2 = 59.7
R4 = -446.518 D4 = 2.41
R5 = −65.423 D5 = 1.94 N3 = 1.7507 ν3 = 27.9
R6 = 5137.502 D6 = 54.84

  FIG. 4 is a cross-sectional view of the illuminance distribution at the end of the illumination range in the configuration of Example 1, and the horizontal axis and the vertical axis are the same as those in FIG. In FIG. 4, since the superposition of each cell is improved by improving the spherical aberration and the like as compared with FIG. 6, the light loss on the left side of the illumination margin boundary A is reduced, and the B light in the illumination margin boundary A is reduced. The decrease in illuminance is also improved. Thus, Numerical Example 2 can improve illumination efficiency and color reproducibility over the comparative example. In the numerical example 2, an effect of improving the deviation due to the wavelength at the end of the illuminance distribution can be obtained as compared with the example 1. However, the spherical aberration becomes larger than the example 1 at the inclination of the end of the distribution. It becomes gentler than the inclination of the end of 1. Further, since the positive lens 28A and the negative lens 29A are not joined as in the first embodiment, there are advantages that the manufacturing becomes easy and the cost can be reduced.

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

  The present invention is applicable to an illumination optical system of a projection display device such as a liquid crystal projector.

20A, 20B ... illumination optical system, 22 ... first lens array (dividing means), 24 ... second lens array (dividing means), 26A, 26B ... first lens group, 27A, 27B ... second lens group, 28A, 28B ... positive lens, 29A, 29B ... negative lens, 40 ... liquid crystal panel (light modulation element)

Claims (10)

An illumination optical system that illuminates a light modulation element that modulates light from a light source with the light,
A splitting unit that splits a light beam from the light source into a plurality of light beams in order along the optical path from the light source side, and a condenser lens system,
The condensing lens system includes a first lens group having a function of condensing the light beam divided by the dividing unit in order along the optical path from the light source side and having a positive refractive index, and a positive refractive index. A second lens group having
The first lens group is composed of a single lens,
The second lens group is composed of one positive lens and one negative lens in order along the optical path from the light source side,
In the second lens group, the focal length of the entire condenser lens system is Fall, the focal length of the first lens group is f1, the Abbe number of the first lens group is ν1, and the second lens group The focal length of the positive lens is f2p, the focal length of the positive lens of the second lens group is ν2p, the focal length of the negative lens of the second lens group is f2n, and the focal length of the positive lens of the second lens group is If the distance is ν2n, in addition to the above action,

It has the effect of correcting chromatic aberration that satisfies
An illumination optical system characterized by that. The illumination optical system according to claim 1, wherein the following conditional expression is satisfied.
The illumination optical system according to claim 1, wherein the following conditional expression is satisfied, where f2 is a combined focal length of the second lens group.
4. The illumination optical system according to claim 1, wherein the following conditional expression is satisfied, where D <b> 12 is an interval between the first lens group and the second lens group. 5.
The following conditional expressions are satisfied, where the Abbe number of the glass material of the first lens group is ν1p and the Abbe number of the glass material of the positive lens of the second lens group is ν2p. 4. The illumination optical system according to claim 1.
60 <ν1p <70
50 <ν2p <70 The following conditional expression is satisfied, where an Abbe number of a glass material constituting the positive lens of the second lens group is ν2p and an Abbe number of a material constituting the negative lens is ν2n. The illumination optical system according to any one of 1 to 5.
20 ≦ ν2p−ν2n ≦ 40   The illumination optical system according to any one of claims 1 to 6, wherein the positive lens and the negative lens of the second lens group are a cemented lens. The space S on the optical axis between the negative lens side surface of the positive lens and the positive lens side surface of the second lens group in the second lens group satisfies the following conditional expression. The illumination optical system according to any one of claims.
0.00147 <S / Fall <0.147 A polarization conversion element that is disposed between the light source and the condenser lens system and aligns the polarization direction of the light from the light source;
A bending mirror that bends light from the polarization conversion element and guides it to the condenser lens system;
The illumination optical system according to claim 1, further comprising:   A projection display device comprising the illumination optical system according to any one of claims 1 to 9.