JP2013145378A - Projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination optical system for a projector with high illumination efficiency.SOLUTION: In an illumination optical system for a projector having a liquid crystal panels 108a to 108c, integrators 101a, 101b, a polarization conversion element 102, a field lens 103, and a return mirror 111 are successively arranged in the advancing direction of a light flux from a light source 100, and a condenser lens 106 and dichroic mirrors 104a, 104b are successively arranged in the advancing direction of the light flux reflected by the return mirror 111. A mirror 105 is arranged in the advancing direction of B-light reflected by the dichroic mirror 104a. A rectangular image of the light source 100 formed on the integrator 101b is magnified and imaged on the display panels 108a, 108b by the field lens 103 and the condenser lens 106. The condenser lens 106 is configured to return the principal ray of the field lens 103 to parallel rays.

Description

  The present invention relates to a projector represented by a liquid crystal projector.

  As an illumination optical system for a liquid crystal projector, an illumination optical system including an integrator for uniformizing the light intensity of a light beam from a light source is known (see Patent Documents 1 and 2). There are various arrangements of the optical elements of the illumination optical system. As typical arrangements of the optical elements, those in which the optical elements are arranged in an L shape, a U shape, an S shape, or the like are known. FIGS. 11, 12, and 13 show examples of L-shaped arrangement, U-shaped arrangement, and S-shaped arrangement, respectively.

  The illumination optical system shown in FIG. 11 is an illumination optical system of a three-plate liquid crystal projector that illuminates the liquid crystal panels 108a to 108c with RGB color lights, respectively, and includes a light source 100, integrators 101a and 101b, a polarization conversion element 102, and a field. A lens 103, dichroic mirrors 104a and 104b, mirrors 105a to 105c, condenser lenses 106a to 106c, and relay lenses 107a and 107b are provided.

  The light source 100 includes a lamp and a reflector typified by an ultra-high pressure mercury lamp, and the light from the lamp is emitted directly or reflected by the reflector and emitted as a substantially parallel light beam. Integrators 101a and 101b, a polarization conversion element 102, a field lens 103, and a dichroic mirror 104a are sequentially arranged in the traveling direction of the light beam emitted from the light source 100. The integrators 101a and 101b are for uniformizing the light intensity of the light beam from the light source 100, and include a plurality of lens cells arranged in a matrix. The polarization conversion element 102 aligns the polarization direction of the light beams from the integrators 101a and 101b, and includes a polarization beam splitter, a phase plate, and the like. The dichroic mirror 104a reflects the B (blue) light of the light flux from the field lens 103 and transmits the remaining R (red) light and G (green) light.

  A mirror 105a is disposed in the traveling direction of the B light reflected by the dichroic mirror 104a, and a condenser lens 106a and a liquid crystal panel 108a are sequentially disposed in the traveling direction of the light (B light) reflected by the mirror 105a.

  A dichroic mirror 104b is arranged in the traveling direction of the R / G light transmitted through the dichroic mirror 104a. The dichroic mirror 104b reflects G light and transmits R light. A condenser lens 106b and a liquid crystal panel 108b are sequentially arranged in the traveling direction of the light (G light) reflected by the dichroic mirror 104b. The relay lens 107a and the mirror 105b are sequentially arranged in the traveling direction of the light (R light) transmitted through the dichroic mirror 104b, and the relay lens 107b and the mirror 105c are sequentially arranged in the traveling direction of the light reflected by the mirror 105b. A condenser lens 106c and a liquid crystal panel 108c are sequentially arranged in the traveling direction of the light reflected by the mirror 105c.

  In the illumination optical system described above, the light beam emitted from the light source 100 is made uniform by the integrators 101 a and 101 b, the light intensity is made uniform, and the polarization direction is aligned by the polarization conversion element 102, and then enters the field lens 103. The light beam that has passed through the field lens 103 is separated into R, G, and B color light by the dichroic mirrors 104a and 104b. The liquid crystal panel 108c is illuminated by the R light, the liquid crystal panel 108b is illuminated by the G light, and the liquid crystal panel 108a is illuminated by the B light.

  The R, G, and B image lights generated by the liquid crystal panels 108 a to 108 c are color-combined by the cross dichroic prism 109 and then projected on the screen by the projection lens 110.

  The illumination optical system with the U-shaped arrangement shown in FIG. 12 is also an illumination optical system of a three-plate liquid crystal projector, but the point that the folding mirror 111 is arranged between the field lens 103 and the dichroic mirror 104a is shown in FIG. Different from the optical system shown. The light beam from the field lens 103 is reflected by the folding mirror 111 approximately 90 degrees and enters the dichroic mirror 104a, and each optical element is arranged in a U shape.

  The S-shaped arrangement of the illumination optical system shown in FIG. 13 is also of a three-plate type liquid crystal projector, but compared with the optical system shown in FIG. 12, dichroic mirrors 104a and 104b, mirrors 105a to 105c, and condenser lenses 106a to 106c. In addition, the relay lenses 107a and 107b are arranged in the opposite direction. In this optical system, the dichroic mirror 104a reflects the R / G light of the light beam from the folding mirror 111 and transmits the remaining B light. A mirror 105a is arranged in the traveling direction of the B light transmitted through the dichroic mirror 104a, and the B light reflected by the mirror 105a is irradiated to the liquid crystal panel 108a through the condenser lens 106a. The dichroic mirror 104b is disposed in the traveling direction of the R / G light, reflects the G light, and transmits the R light. The G light reflected by the dichroic mirror 104b is applied to the liquid crystal panel 108b through the condenser lens 106b. The R light transmitted through the dichroic mirror 104b sequentially passes through the relay lens 107a, the mirror 105b, the relay lens 107b, the mirror 105c, and the condenser lens 106c and is irradiated on the liquid crystal panel 108c.

JP 2001-228440 A JP 2004-045907 A

  The polarization conversion element has a plurality of polarization conversion units provided corresponding to the intervals of the arc images of the light sources projected in the vicinity of the optical axis of each lens cell of the integrator. The polarization directions of the light beams are aligned. In such a polarization conversion element, light that is out of the effective aperture of each polarization conversion unit (the aperture that defines the range in which polarization conversion is possible) out of the incident light does not contribute to polarization conversion. The polarization conversion efficiency will decrease.

  In the illumination optical system that superimposes the light beam that has passed through each lens cell of the first integrator disposed on the light source side on the liquid crystal panel surface, it is formed on the second integrator in order to improve the polarization conversion efficiency. It is necessary to reduce the amount of light deviating from the effective aperture of the polarization conversion element by making the size of the arc image of the light source as small as possible. However, in the above-described illumination optical systems of the L-shaped arrangement, the U-shaped arrangement, and the S-shaped arrangement, the combined focal length of the field lens and the condenser lens is long, so that the focal length of the first integrator is necessarily long. For this reason, the ratio (magnification) between the size of the arc of the light source and the size of the arc image formed on the second integrator increases, and the arc image formed on the second integrator becomes large. In particular, in a U-shaped arrangement or S-shaped arrangement illumination optical system including a folding mirror between the field lens and the condenser lens, the combined focal length of the field lens and the condenser lens is inevitably longer than that of the L-shaped arrangement. It becomes inefficient.

  Note that by inserting a new lens between the field lens and the condenser lens, it is possible to shorten the combined focal length of the field lens and the condenser lens and to reduce the arc image formed on the second integrator. is there. However, in this case, as the new lens is added, the transmittance decreases and the cost increases.

  An object of the present invention is to solve the above problems and provide a projector with high illumination efficiency.

In order to achieve the above object, a projector according to the present invention provides:
A projector having a light source and first to third transmissive liquid crystal panels,
A first integrator comprising a plurality of lens cells for dividing the light beam emitted from the light source into a plurality of partial light beams and condensing the plurality of partial light beams,
A second integrator comprising a plurality of lens cells into which the plurality of partial light beams are incident;
A polarization conversion element that aligns the polarization direction of the light beam that has passed through each lens cell of the second integrator;
First color separation means for separating a light beam from the polarization conversion element into a plurality of color lights having different wavelengths;
A second color separation means for further separating the light beam transmitted through the first color separation means into a plurality of color lights having different wavelengths,
The light beam reflected by the first color separation means irradiates the first transmissive liquid crystal panel,
The light beam transmitted through the first color separation means and reflected by the second color separation means irradiates the second transmissive liquid crystal panel,
The light beam transmitted through the second color separation means irradiates the third transmission type liquid crystal panel,
In the optical path between the polarization conversion element and the first color separation means, the light beam that has passed through each lens cell of the first integrator is superimposed on the first to third transmissive liquid crystal panels. A field lens and a first condenser lens are disposed;
In the optical path between the second color separation means and the third transmissive liquid crystal panel, a relay lens and a second condenser lens are sequentially arranged.
The first condenser lens is disposed on the first color separation means side, and is configured to make principal rays of light beams that have passed through the field lens substantially parallel to each other.

  In the projector of the present invention described above, the light beam that has passed through each lens cell of the first integrator is incident on the plurality of display panels substantially in parallel by the field lens and the condenser lens, and is superimposed on the plurality of display panels. It is like that. In this configuration, the distance between the field lens and the condenser lens (the distance on the light beam passing through the center of each lens) is equal to the combined focal length of the field lens and the condenser lens. In the projector of the present invention, the distance between these lenses can be shortened by using a field lens and a condenser lens having a short combined focal length as compared with the conventional illumination optical systems shown in FIGS. By shortening the combined focal length of the field lens and the condenser lens, it is possible to realize an optical system with a short focal length of the first integrator. Therefore, the projector according to the present invention is compared with the conventional illumination optical system. Thus, the arc image of the light source formed on the second integrator can be reduced by the amount of the combined focal length of the field lens and the condenser lens being short.

  According to the present invention, compared with the conventional illumination optical system, the arc image of the light source formed on the second integrator by each lens cell of the first integrator can be reduced, and each polarization of the polarization conversion element can be reduced. Since the amount of light deviating from the effective opening of the conversion unit can be reduced, there is an effect that the illumination efficiency is improved.

It is a schematic diagram which shows the structure of the illumination optical system of the liquid crystal projector which is the 1st Embodiment of this invention. It is a principle explanatory view of optical element arrangement of the illumination optical system of the projector of the present invention. It is a figure for demonstrating formation of the arc image by an integrator. It is a figure for demonstrating the relationship between the space | interval of a field lens and a condenser lens, and the synthetic | combination focal distance of a field lens and a condenser lens. It is a schematic diagram which shows the structure of the illumination optical system of the liquid crystal projector which is the 2nd Embodiment of this invention. It is a figure which shows the design data of the illumination optical system which is one Example of this invention. It is a figure which shows the design data of the illumination optical system which is a comparative example. It is a schematic diagram which shows the arc image formed on the integrator in the illumination optical system based on the design data shown in FIG. It is a schematic diagram which shows the arc image formed on the integrator in the illumination optical system based on the design data shown in FIG. It is the figure which showed the difference of the illumination efficiency of the illumination optical system of an Example, and the illumination optical system of a prior art example. It is a schematic diagram which shows the structure of the illumination optical system of the conventional L-shape arrangement | positioning. It is a schematic diagram which shows the structure of the illumination optical system of the conventional U shape arrangement | positioning. It is a schematic diagram which shows the structure of the illumination optical system of the conventional S character arrangement.

  Next, embodiments of the present invention will be described with reference to the drawings.

  First, the principle of the present invention will be described. FIG. 2 is a diagram for explaining the optical element arrangement of the illumination optical system of the projector according to the present invention.

  Referring to FIG. 2, the illumination optical system of the projector of the present invention is an optical system that illuminates the liquid crystal panel LCD, and integrators IT1, IT2, polarization conversion element PBS, field lens FL, and condenser lens CL are sequentially arranged from the light source side. The arc image (rectangular image) of the light source formed on the integrator IT2 by the integrator IT1 is formed on the liquid crystal panel LCD while being enlarged by the field lens FL and the condenser lens CL. . Between the integrator IT1 and the liquid crystal panel LCD, an imaging magnification relationship represented by the following formulas 1 and 2 is established.

Where M is the horizontal magnification of IT1 and LCD, l _IT1 is the size (outer diameter) of the lens cell constituting IT1, l _LCD is the length of the long side of the LCD, and f _IT1 is the focal length of the lens cell of IT1 , F _FL · _CL is the FL · CL combined focal length. From Equation 2, when the FL / CL combined focal length f _FL · _CL is a relatively long optical system, such as the U-shaped arrangement shown in FIG. 12 or the S-shaped arrangement shown in FIG. 13, the focal length f of IT1. _It can be seen that _{IT1 is} also relatively long.

  FIG. 3 is a diagram for explaining the formation of an arc image. An arc image of the light source is formed on the integrator IT2 by the integrator IT1. The size of the arc image formed on this IT2 is given by the following expression 3.

Here, l _arc is the effective aperture of the arc image formed on IT2, l _LAMP is the effective aperture of the light source arc, NA is the numerical aperture of the light source, and NA ′ is the numerical aperture of IT1. The numerical aperture NA ′ of IT1 can be expressed by Equation 4 below.

Here, θ _i is the light collection angle of IT1.

  Substituting equation 4 into equation 3,

Get.

Further, the light collection angle θ _i of IT1 can be expressed by the following Expression 6.

  Substituting equation 6 into equation 5,

Get. Furthermore, when Expression 1 and Expression 2 are substituted into Expression 7,

Get. From Equation 8, it can be seen that the arc image l _arc becomes large in the case of an optical system having a relatively long FL / CL combined focal length f _FL · _CL such as a U-shaped arrangement or an S-shaped arrangement.

FIG. 4 is a diagram for explaining the relationship between the interval between FL and CL and the FL / CL combined focal length f _FL · _CL . The FL · CL combined focal length f _FL · _CL is given by the following Expression 9.

Here, f _FL is the focal length of the field lens, f _CL is the focal length of the condenser lens, and d is the distance between the FL and CL (the distance between the lens centers).

  In an optical system configured so that the principal ray of CL is parallel light is CL, the FL-CL interval d can be expressed by the following equation.

  Substituting Equation 10 into Equation 9,

Get. From Equation 11, the FL-CL interval d and the FL · CL combined focal length f _FL · _CL have the same relationship. Therefore, by shortening the FL-CL interval d, the arc image l _arc formed on the IT 2 is reduced. You can see that you can. According to this knowledge, even in an optical system having a relatively long FL / CL combined focal length f _FL / _CL such as U-shaped arrangement or S-shaped arrangement, CL is configured so that the principal ray of FL is substantially parallel light. In this case, by shortening the FL-CL interval d, the FL / CL combined focal length f _FL · _CL can be shortened, and the arc image l _arc can be reduced. By reducing the arc image l _arc , the polarization conversion efficiency is improved and the illumination efficiency is improved.

Note that when the FL-CL interval d is shortened, the principal point positions of the FL / CL combined focal lengths f _FL · _CL and FL and CL change, so that the focal position moves and the focus is not focused on the LCD. End up. Therefore, when the FL-CL interval d is changed, it is necessary to adjust the focal length fFL of the _FL and the focal length fCL of the _CL at the same time to focus on the LCD.

The focal length f _{FL of FL} and the focal length f _{CL of} CL when the FL-CL interval d is changed can be obtained as follows.

  When the interval between FL and CL after the change is L, the interval L is given by the following Expression 12.

  Substituting Equation 11 into Equation 12,

Get. Therefore, when the interval between FL and CL is shortened by Δd,

The focal length f _{FL of FL} and the focal length f _CL of _CL are determined so as to satisfy the following relational expression.

  Further, in the polarization conversion element PBS, light that is out of the effective aperture of each polarization conversion unit among incident light does not contribute to polarization conversion. In order to improve the polarization conversion efficiency, the size of the arc image (rectangular image) of the light source formed on the integrator IT2 by each lens cell of the integrator IT1 is the range of the effective aperture of each polarization conversion unit of the polarization conversion element. It is desirable to set the FL-CL interval d so as to be within the range. Below, the desirable range of FL-CL space | interval d is demonstrated.

When the aperture pitch of the polarization conversion element PBS (same as the effective aperture of the polarization conversion unit) is 1 _PBS ,

If this holds, the size of the arc image (rectangular image) of the light source formed on the integrator IT2 will be within the range of the effective aperture of each polarization conversion portion of the polarization conversion element, and the polarization conversion efficiency will be calculated. The loss of can be eliminated.

  Here, when Expression 8 is substituted into Expression 16,

  Get. If the optical system is designed so that the FL-CL interval d satisfies the condition of Expression 17, the size of the arc image formed on the integrator IT2 is equal to or less than the size of the effective aperture of the polarization conversion element PBS. Loss of polarization conversion efficiency can be reduced. The lower limit of the FL-CL interval d can be set as appropriate according to the design.

In the present invention, when the principle explained above is used and an optical system such as a U-shaped arrangement or an S-shaped arrangement is configured such that a principal ray whose CL is FL becomes parallel light, the FL-CL interval d and FL Based on the knowledge that the CL combined focal lengths f _FL and _CL are equal, the FL-CL interval d is shortened to realize an optical system with a shorter FL / CL combined focal length f _FL and _CL . According to the optical system thus realized, the arc image l _arc formed on the IT 2 can be reduced, so that the illumination efficiency can be improved.

  The illumination optical system is designed so that the FL-CL interval d satisfies the condition of Expression 17. Thereby, an illumination optical system with higher polarization conversion efficiency can be realized.

Hereinafter, as an embodiment of the present invention, an optical system having a U-shaped arrangement in which the above-described principle is applied and the FL-CL interval d is shortened to reduce the arc image l _arc formed on the IT 2 will be described.

(First embodiment)
FIG. 1 shows a configuration of an illumination optical system of a liquid crystal projector that is the first embodiment of the present invention. Referring to FIG. 1, in the illumination optical system of the present embodiment, the condenser lenses 106a and 106b are deleted from the optical system shown in FIG. 12, and the condenser lens 106 is disposed between the dichroic mirror 104a and the folding mirror 111. In other words, the light flux from the light source 100 divided by the integrator 101a is superimposed and irradiated on the liquid crystal panels 108a and 108b by the field lens 103. The arc image of the light source 100 is formed on the integrator 101b and in the vicinity thereof by the integrator 101a.

  The condenser lens 106 is configured to make the principal rays of the light beams that have passed through the field lens 103 disposed between the polarization conversion element 102 and the folding mirror 111 substantially parallel to each other. The distance is equal to the combined focal length of the field lens 103 and the condenser lens 106. Therefore, by reducing the distance between the field lens 103 and the condenser lens 106, an optical system having a short combined focal length of the field lens 103 and the condenser lens 106 can be provided.

  In the illumination optical system of the present embodiment, the distance between the field lens 103 and the condenser lens 106 is smaller than the distance between the field lens 103 and the condenser lens 106a (or condenser lens 106b) in the U-shaped optical system shown in FIG. Therefore, the combined focal length of the field lens and the condenser lens is smaller than that of the optical system shown in FIG. Therefore, compared with the optical system shown in FIG. 12, the arc image formed on the integrator 101b and in the vicinity thereof can be reduced, and the amount of vignetting in the polarization conversion element 102 is reduced correspondingly, and polarization conversion is performed. Efficiency is improved.

  Further, in the illumination optical system of the present embodiment, the cost can be reduced because the number of condenser lenses is smaller than that of the optical system shown in FIG.

  In the optical path having the relay lenses 107a and 107b, since the optical path length from the integrator 101a to the liquid crystal panel 108c is longer than the other optical paths, it is necessary to correct the optical path. Therefore, the optical path length is corrected by the relay lenses 107a and 107b and the condenser lens 107c. Specifically, the image is inverted once by the relay lens 107a and the relay lens 107b, and the inverted image is irradiated to the liquid crystal panel 108c by the condenser lens 107c so that the principal rays thereof are substantially parallel.

  In this embodiment, in order to realize an illumination optical system with higher polarization conversion efficiency, it is desirable that the distance between the field lens 103 and the condenser lens 106 is set so as to satisfy the above-described Expression 17.

(Second Embodiment)
FIG. 5 shows a configuration of an illumination optical system of a liquid crystal projector according to the second embodiment of the present invention. Referring to FIG. 5, in the illumination optical system of the present embodiment, in the illumination optical system shown in FIG. 12, the condenser lenses 106a and 106b are deleted, and the condenser lens 116a is placed between the dichroic mirror 104a and the mirror 105a. The condenser lens 116b is respectively disposed between the 104a and 104b, and the light beam from the light source 100 divided by the integrator 101a passes through the field lens 103 and the condenser lenses 116a and 116b, and on the liquid crystal panels 108a and 108b. It is comprised so that it may overlap and irradiate.

  Each of the condenser lenses 116 a and 116 b is configured to make the principal rays of the light beams that have passed through the field lens 103 disposed between the polarization conversion element 102 and the folding mirror 111 substantially parallel to each other. Since the distance between the field lens 103 and the condenser lens 116a is equal to the combined focal length of the field lens 103 and the condenser lens 116a, the distance between the field lens 103 and the condenser lens 116a is reduced to reduce the distance between the field lens 103 and the condenser lens 116a. An optical system with a short combined focal length 116a can be provided. Similarly, since the distance between the field lens 103 and the condenser lens 116b is equal to the combined focal length of the field lens 103 and the condenser lens 116b, the distance between the field lens 103 and the condenser lens 116b is reduced to reduce the field lens 103. And an optical system having a short combined focal length of the condenser lens 116b.

  In the illumination optical system of the present embodiment, each distance between the field lens 103 and the condenser lenses 116a and 116b is the same as that between the field lens 103 and the condenser lenses 106a and 106b in the U-shaped arrangement optical system shown in FIG. Since the distance is smaller than the distance, the combined focal length of the field lens 103 and the condenser lens 116a and the combined focal length of the field lens 103 and the condenser lens 116b are both smaller than those in the optical system shown in FIG. As described above, also in the present embodiment, the distance between the field lens and the condenser lens is reduced and the combined focal length of the field lens and the condenser lens is reduced, so that an arc image formed on the integrator 101b is formed. The amount of vignetting in the polarization conversion element 102 is reduced correspondingly, and the polarization conversion efficiency is improved.

  Also in this embodiment, in order to realize an illumination optical system with higher polarization conversion efficiency, it is desirable to set each interval between the field lens 103 and the condenser lenses 116a and 116b so as to satisfy the above-described Expression 17.

(Example)
FIG. 6 shows design data of optical elements in the illumination optical system shown in FIG. This design data is calculated using existing optical simulation software. In FIG. 6, “IT1” is the integrator 101a, “IT2” is the integrator 101b, “PBS” is the polarization conversion element 102, “FL” is the field lens 103, “CL” is the condenser lens 116a (or 116b), and “LCD”. Corresponds to the liquid crystal panel 108a (or 108b), respectively. In the “Radius” column, the radius of curvature of each surface of the arranged optical elements (IT1, IT2, PBS, FL, CL, LCD) is indicated in mm. “∞” in the “Radius” column indicates a plane. In the “Thickness” column, the thickness or interval of the optical element is indicated in mm. In the “Index” column, the refractive index of the optical element is shown. The interval between the optical elements is a linear distance converted value.

  In the illumination optical system of the present embodiment, the integrator IT1 has a radius of curvature of the entrance surface (incident surface of each lens cell) of 14.9 mm, a flat exit surface, a thickness of 3.16 mm, and a refractive index of 1.474. Has been. The interval between the integrator IT1 and the integrator IT2 is 26.9 mm.

  The integrator IT2 has a flat entrance surface, a radius of curvature of the exit surface (exit surface of each lens cell) of 14.9 mm, a thickness of 3.16 mm, and a refractive index of 1.474. The distance between the integrator IT2 and the polarization conversion element PBS is 2.44 mm. Here, the minus sign in the radius of curvature in FIG. 6 indicates that the curve is convex in the light traveling direction.

The polarization converting element PBS has a flat entrance / exit surface, a thickness of 4 mm, and a refractive index of 1.523. The distance between the polarization conversion element PBS and the field lens (FL) is 2 mm. Therefore, the effective aperture l _PBS of the polarization conversion unit (polarization conversion element PBS) is 4 mm.

  In the field lens (FL), the radius of curvature of the entrance surface is 257 mm, the exit surface is flat, the thickness is 5 mm, and the refractive index is 1.624. The distance between the field lens (FL) and the condenser lens (CL) is 158.3 mm.

  The condenser lens (CL) has an incident surface with a curvature radius of 101 mm, an output surface with a flat surface, a thickness of 7 mm, and a refractive index of 1.624. The distance between the condenser lens (CL) and the liquid crystal panel (LCD) is 92.7 mm.

  The liquid crystal panel (LCD) is an XGA panel (4: 3) having a size of 1 inch, and its long side is 20.32 mm (the size is not shown).

The effective diameter (l _LAMP ) of the light source arc is 1.1 mm, and the numerical aperture (NA) of the light source is 0.766 (not shown).

(Comparative example)
FIG. 7 shows design data of optical elements in the illumination optical system having the U-shaped arrangement shown in FIG. This design data is also calculated using existing optical simulation software. In FIG. 7, “IT1” is the integrator 101a, “IT2” is the integrator 101b, “PBS” is the polarization conversion element 102, “FL” is the field lens 103, “CL” is the condenser lens 106a (or 106b), and “LCD”. Corresponds to the liquid crystal panel 108a (or 108b), respectively. In the “Radius” column, the radius of curvature of each surface of the arranged optical elements (IT1, IT2, PBS, FL, CL, LCD) is indicated in mm. “∞” in the “Radius” column indicates a plane. In the “Thickness” column, the thickness or interval of the optical element is indicated in mm. In the “Index” column, the refractive index of the optical element is shown. The interval between the optical elements is a linear distance converted value.

  In the illumination optical system of this comparative example, the integrator IT1 has a radius of curvature of the entrance surface (incident surface of each lens cell) of 22.8 mm, a plane of exit, a thickness of 3.16 mm, and a refractive index of 1.474. Has been. The interval between the integrator IT1 and the integrator IT2 is 43.6 mm.

  The integrator IT2 has a flat entrance surface, a radius of curvature of the exit surface (the exit surface of each lens cell) of 22.8 mm, a thickness of 3.16 mm, and a refractive index of 1.474. The distance between the integrator IT2 and the polarization conversion element PBS is 2.44 mm.

  Here, the minus sign in the radius of curvature in FIG. 7 indicates that the radius of curvature is convex in the traveling direction of light, which is the same definition as in the previous embodiment.

The polarization converting element PBS has a flat entrance / exit surface, a thickness of 4 mm, and a refractive index of 1.523. The distance between the polarization conversion element PBS and the field lens (FL) is 2 mm. Therefore, the effective aperture l _PBS of the polarization conversion unit (polarization conversion element PBS) is 4 mm.

  In the field lens (FL), the radius of curvature of the incident surface is 163 mm, the exit surface is flat, the thickness is 5 mm, and the refractive index is 1.624. The distance between the field lens (FL) and the condenser lens (CL) is 244 mm.

  The condenser lens (CL) has a radius of curvature of the incident surface of 154.3 mm, a flat exit surface, a thickness of 7 mm, and a refractive index of 1.624. The distance between the condenser lens (CL) and the liquid crystal panel (LCD) is 6.9 mm.

  The liquid crystal panel (LCD) is an XGA panel (4: 3) having a size of 1 inch, and its long side is 20.32 mm (the size is not shown).

The effective diameter (l _LAMP ) of the light source arc is 1.1 mm, and the numerical aperture (NA) of the light source is 0.766 (not shown).

  Here, when the limit value of the FL-CL interval is obtained from Expression 17, it is 190.8 mm. In the illumination optical system of the above comparative example, the FL-CL interval is 244 mm, whereas in the illumination optical system of the above embodiment, the FL-CL interval is 158.3, which is shorter than the comparative example. Further, in the embodiment, the condition of Expression 17 is satisfied, and the size of the arc image formed on the integrator IT2 is equal to or smaller than the size of the effective aperture of the polarization conversion element PBS, thereby reducing the loss of polarization conversion efficiency. Can be expected to do.

  FIG. 8 schematically shows an arc image formed on IT2 in the illumination optical system based on the design data shown in FIG. 6, and FIG. 9 shows on IT2 in the illumination optical system based on the design data shown in FIG. An arc image formed is schematically shown in FIG.

  As shown in FIGS. 8 and 9, the arc image formed on IT2 by each lens cell of IT1 spreads radially from the center of IT2 in the outer circumferential direction. In the polarization conversion element PBS, each polarization conversion unit is arranged corresponding to the interval of the arc image formed by each lens cell, and when the size of the arc image becomes larger than the effective aperture of the polarization conversion unit, the polarization conversion efficiency Cause a decline. Since the size of each arc image shown in FIG. 8 is smaller than that shown in FIG. 9, the illumination optical system based on the design data shown in FIG. 6 uses the illumination based on the design data shown in FIG. It can be seen that the polarization conversion efficiency is higher than that of the optical system.

  FIG. 10 shows the difference between the illumination efficiency of each optical element of the illumination optical system of the embodiment (FIG. 6) and the illumination efficiency of each optical element of the illumination optical system of the conventional example (FIG. 7). When this value is positive, the example shows that the illumination efficiency is improved by that amount compared to the conventional example. As can be seen from FIG. 10, in the illumination optical system of the embodiment, compared with the illumination optical system of the conventional example, the polarization conversion element PBS improves the illumination efficiency by about 8 points, and finally the illumination optical system of about 13 points. Improved efficiency. Here, the improvement of the illumination efficiency by 13 points means that the illumination efficiency is changed from 60% to 73%, for example.

  As described above, the embodiment of the present invention has been described by taking the U-shaped arrangement of the illumination optical system as an example, but the present invention is not limited to the U-shaped arrangement. For example, in the S-shaped arrangement illumination optical system shown in FIG. 13, by applying the arrangement of the field lens and the condenser lens as shown in FIGS. 1 and 5, the illumination optics of the first and second embodiments are applied. Has the same effect as the system. Similarly, in the illumination optical system having the L-shaped arrangement shown in FIG. 11, the arrangement of the field lens and the condenser lens as shown in FIG. 1 and FIG. The same effect as the illumination optical system is achieved.

  In the illumination optical system described above, it is possible to appropriately determine which color component is used as the optical path separated by the dichroic mirrors 104a and 104b according to the design.

DESCRIPTION OF SYMBOLS 100 Light source 101a, 101b Integrator 102 Polarization conversion element 103 Field lens 104a, 104b Dichroic mirror 105a-105c Mirror 106, 106c Condenser lens 107a, 107b Relay lens 108a-108c Liquid crystal panel 109 Cross dichroic prism 110 Projection lens 111 Folding mirror

Claims (5)

A projector having a light source and first to third transmissive liquid crystal panels,
A first integrator comprising a plurality of lens cells for dividing the light beam emitted from the light source into a plurality of partial light beams and condensing the plurality of partial light beams,
A second integrator comprising a plurality of lens cells into which the plurality of partial light beams are incident;
A polarization conversion element that aligns the polarization direction of the light beam that has passed through each lens cell of the second integrator;
First color separation means for separating a light beam from the polarization conversion element into a plurality of color lights having different wavelengths;
A second color separation means for further separating the light beam transmitted through the first color separation means into a plurality of color lights having different wavelengths,
The light beam reflected by the first color separation means irradiates the first transmissive liquid crystal panel,
The light beam transmitted through the first color separation means and reflected by the second color separation means irradiates the second transmissive liquid crystal panel,
The light beam transmitted through the second color separation means irradiates the third transmission type liquid crystal panel,
In the optical path between the polarization conversion element and the first color separation means, the light beam that has passed through each lens cell of the first integrator is superimposed on the first to third transmissive liquid crystal panels. A field lens and a first condenser lens are disposed;
In the optical path between the second color separation means and the third transmissive liquid crystal panel, a relay lens and a second condenser lens are sequentially arranged.
The projector is characterized in that the first condenser lens is disposed on the first color separation means side and is configured so that chief rays of light beams that have passed through the field lens are substantially parallel to each other. .   2. The projector according to claim 1, wherein the second condenser lens is configured such that principal rays of light beams that have passed through the relay lens are further substantially parallel to each other.   The projector according to claim 2, wherein an interval between the first condenser lens and the field lens is equal to a combined focal length of the first condenser lens and the field lens. The polarization conversion element includes a plurality of polarization conversion units arranged corresponding to intervals of arc images of the light source formed on the second integrator,
The effective aperture of the arc image of the light source formed on the second integrator by each lens cell of the first integrator is l _arc , the effective aperture of the _{arc of} the light source is l _LAMP , and the numerical aperture of the light source is NA The length of the long side of the plurality of display panels is l _LCD , the effective aperture of each of the plurality of polarization converters is l _PBS , and the first distance between the field lens and the first condenser lens is d. When the distance d is

The projector according to claim 2, wherein the projector is set so as to satisfy the following condition.   5. The apparatus according to claim 1, further comprising a mirror that is disposed between the field lens and the first condenser lens and reflects a light beam from the field lens toward the first condenser lens. The projector according to item.

Images