JP2005165137A - Illuminating optical system and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an optical system compact while securing uniformity of brightness in the illuminating area of image forming elements. <P>SOLUTION: An illuminating optical system comprises beam division means 3a, 3b for dividing a beam from a light source into a plurality of beams, a color decomposition optical system for color-decomposing the beams from the beam division means and leading the color-decomposed beams to a plurality of image forming elements and a color composition optical system for compositing beams from these image forming elements and leading the composited beam to a projecting optical system. The color decomposition optical system includes a dichroic mirror 6 and polarized light separation elements 10a, 10b on which a beam from the dichroic mirror 6 is made incident and a converging optical system 5 is arranged between the beam division means 3a, 3b and the polarized light separation elements 10a, 10b. The converging optical system 5 includes 1st and 2nd lenses 5a, 5b arranged between the beam division means 3a, 3b and the dichroic mirror 6 and 3rd lenses 5c(5c') arranged between the dichroic mirror 6 and respective polarized light separation elements 10a, 10b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical system used in an image display apparatus such as a projector.

  As an image display device, Patent Document 1 and Patent Document 2 propose a device using a reflective liquid crystal display element (image forming element) and a polarization beam splitter.

  In the image display device proposed in Patent Document 1, four polarizing beam splitters are used, and in the one proposed in Patent Document 2, three polarizing beam splitters and a dichroic mirror are used.

  FIG. 7 shows an optical configuration of the image display device proposed in Patent Document 2. In this apparatus, after the light beams emitted from the light source 101 and the reflector 102 are incident on the condenser lens 109 via the first and second fly-eye lenses 103a and 103b and the polarization conversion element 104 and receive a condensing function. Then, the light enters the field lens 108 through the mirrors 106 and 107. A light beam emitted from the field lens 108 is separated into a green light component and a red and blue light component by a dichroic mirror 109. The red and blue light components are separated into a red light component and a blue light component by the first polarizing beam splitter 110RB through the first color selective phase difference plate 112, and are respectively reflected in the reflective liquid crystal display elements 115B and 115R. Led.

  On the other hand, the green light component is incident on the second polarizing beam splitter 110G via the second color selective phase difference plate 113, and is guided to the reflective liquid crystal display element 115G from here. Thereafter, the three color light components modulated by the liquid crystal display elements 115B, 115R, and 115G are combined and projected from the projection lens 116 onto a screen (not shown) to display a color image.

Here, the color selective phase difference plate has a function of converting the polarization direction of light in a predetermined wavelength region by 90 degrees in the wavelength region of visible light and not changing the polarization direction of light of other wavelengths. .
US Patent 6,183,091 (FIG. 1 etc.) JP 2001-154152 A (paragraphs 0042-0049, FIG. 1 etc.)

  In general, even if the polarization beam splitter exhibits an ideal polarization separation performance as shown in FIG. 8A with respect to light incident at an incident angle of 45 degrees, the light beam is incident on the light incident at an angle shifted from 45 degrees. On the other hand, an incomplete separation characteristic as shown in FIG. This is because, in an optical thin film formed on a polarizing beam splitter, when the refractive index of the thin film is n, the thickness of the thin film is d, and the incident angle of light is θ, the optical thin film acts on the optical performance at nd cos θ. This is because the polarization separation characteristic changes depending on the incident angle θ.

  For this reason, in order to prevent unevenness in brightness and color in the projected image, the illumination light flux reaching the reflective liquid crystal display element must be in a parallel (telecentric) state on the reflective liquid crystal display element. Don't be.

  However, as in the optical system shown in FIG. 7, the first and second fly-eye lenses 103a and 103b, the condenser lens 105, and the field lens 108 cause an illumination area having a uniform light amount distribution on the reflective liquid crystal display element. When the reflective liquid crystal display element is arranged at the focal position of the system in which the condenser lens 105 and the field lens 108 are combined, the size of the illumination area is the magnification of β of the first fly-eye lens 103a. The size of each lens becomes an enlarged size.

here,
Magnification β = fc / ff2
Fc is the focal length of the composite system of the condenser lens 109 and the field lens 110, and ff2 is the focal length of the second fly-eye lens 103a.

  Further, in order to achieve a telecentric state from the field lens 108 to the reflective liquid crystal display element, the focal position of the combined system of the condenser lens 105 and the field lens 108 obtained from the reflective liquid crystal display element side is set to the first fly-eye. It must be set near the condensing point of the lens 103a.

Here, the use efficiency of the illumination light can be increased by providing the condensing point of the first fly-eye lens 103a in the vicinity of the second fly-eye lens 103b. Therefore, the condenser lens 105 is positioned in the vicinity of the focal point of the synthetic system of the condenser lens 105 and the field lens 108, and the focal length fc of the synthetic system of the condenser lens 105 and the field lens 108 and the focal length ff of the field lens 110 are In between
ff ≒ fc
The relationship will be established.

  For this reason, it is necessary to leave a gap corresponding to the focal length ff of the field lens 108 between the condenser lens 105 and the field lens 108, which increases the size of the optical system from the light source to the color separation system. .

  An object of the present invention is to downsize an illumination optical system including a color separation system (particularly, a polarization separation element) from a light source while ensuring uniformity of brightness within an illumination area of an image forming element. Accordingly, it is an object to reduce the size of the entire image display apparatus.

  In order to achieve the above object, the present invention provides a light beam splitting unit that splits a light beam from a light source into a plurality of colors, and a color separation optical system that color-separates the light beam from the light beam splitting unit and guides it to a plurality of image forming elements. And an illumination optical system. The color separation optical system includes a dichroic mirror and a polarization separation element on which a light beam from the dichroic mirror is incident, and a condensing optical system is provided between the light beam dividing unit and the polarization separation element. The condensing optical system includes a first lens and a second lens arranged in order from the light source side between the light beam splitting unit and the dichroic mirror, and a third lens arranged between the dichroic mirror and the polarization separation element. Including a lens.

  Specifically, the following conditions should be satisfied.

−2.5 <f2 / fc <−1 (1)
Here, fc is the focal length of the entire focusing optical system, and f2 is the focal length of the second lens.

The present invention also relates to an illumination optical system that includes a dichroic mirror and a polarization separation element, and includes a color separation optical system that separates a light beam from a light source and guides it to a plurality of image forming elements. A first optical system having refractive power is provided between the dichroic mirror and the polarization separation element.
A light beam splitting unit that splits the light beam from the light source into a plurality of parts is provided between the light source and the dichroic mirror, and a second optical system having a refractive power is provided between the light beam splitting unit and the dichroic mirror. Also good.
Here, the first optical system and the second optical system have at least one refractive optical element, and may have two or more lenses. “Having refractive power” means that the refractive power is not zero.
When the optical system including the first optical system and the second optical system is a condensing optical system, and the second optical system includes the first and second lenses in order from the light source side, 1) It is preferable to satisfy the equation.

  According to the present invention, by providing the condensing optical system having the lens arrangement as described above between the light source and the polarization separation element of the color separation system, the uniformity of the brightness in the illumination area of the image forming element is sufficiently obtained. While ensuring, the illumination optical system including the color separation system (particularly, the polarization separation element) from the light source can be made compact. Therefore, it is possible to reduce the size of the image display device equipped with the illumination optical system.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows the configuration of a display optical system that is Embodiment 1 of the present invention. In the figure, 1 is a discharge lamp that emits white light with a continuous spectrum, and 2 is a reflector that condenses light from the discharge lamp 1 in a predetermined direction. The discharge lamp 1 and the reflector 2 constitute a light source unit.

  3a is a first fly-eye lens in which a plurality of rectangular lenses are arranged in a matrix, and 3b is a second fly-eye lens having a plurality of lenses corresponding to individual lenses of the first fly-eye lens 3a. . These fly-eye lenses 3a and 3b constitute light beam splitting means referred to in the claims. A polarization conversion element 4 aligns non-polarized light from the second fly-eye lens 3a with polarized light having a predetermined polarization direction.

  Reference numerals 5a and 5b respectively denote a first condenser lens (first lens) and a second condenser lens (second lens) arranged in order from the light source side between the fly-eye lenses 3a and 3b and a dichroic mirror 6 described later. And the second optical system referred to in the claims.

  Reference numerals 5c and 5c ′ denote field lenses (third lenses) disposed between the dichroic mirror 6 and first and second polarizing beam splitters 10a and 10b, which will be described later, respectively. The first optical system is configured.

  Here, the first condenser lens 5a has a positive refractive power, and the second condenser lens 5b has a negative refractive power. The field lenses 5c and 5c 'have a positive refractive power. Having a refractive power means that the refractive power is not zero.

  In the present embodiment, the second optical system is composed of two lenses, and the first optical system is composed of one lens. However, the number of lenses constituting each optical system is not limited to these. It may be one, two, or three or more.

  The dichroic mirror 6 transmits light in the blue (B) and green (G) wavelength regions and reflects light in the red (R) wavelength region. Reference numeral 7 denotes a color filter that partially cuts light in a wavelength region between G and R.

  Reference numerals 8a and 8b respectively denote a first color selective phase difference plate and a second color selective phase difference plate that convert the polarization direction of the G light by 90 degrees and do not convert the polarization direction of the B light. 9 is a half-wave plate. Reference numeral 14 denotes a polarizing plate that does not transmit polarized light having a predetermined polarization direction but transmits polarized light having a polarization direction orthogonal to the polarization direction.

  Reference numerals 10a, 10b, and 10c denote a first polarization beam splitter, a second polarization beam splitter, and a third polarization beam splitter that transmit P-polarized light and reflect S-polarized light, respectively. Reference numerals 11r, 11g, and 11b form an original image, reflect an incident light beam, and modulate and emit an image for reflection, a red reflective liquid crystal display element, a green reflective liquid crystal display element, and a blue reflective liquid crystal display element. It is a reflective liquid crystal display element. 12r, 12g, and 12b are a quarter wavelength plate for red, a quarter wavelength plate for green, and a quarter wavelength plate for blue. Reference numeral 13 denotes a projection lens.

  The first condenser lens 5a, the second condenser lens 5b, and the field lenses 5c and 5c 'constitute the condensing optical system 5. The dichroic mirror 6 and the first and second polarization beam splitters 10a and 10b constitute a color separation optical system, and the first to third polarization beam splitters 10a to 10c constitute a color synthesis optical system. In this embodiment, the optical system from the light source 1 to the first and second polarization beam splitters 10a and 10b is also referred to as an illumination optical system.

  Next, the optical action in the present embodiment will be described. Light emitted from the discharge lamp 1 is collected in a predetermined direction by the reflector 2. Here, the reflector 2 has a paraboloid shape, and light from the focal position of the paraboloid becomes a light beam parallel to the axis of symmetry of the paraboloid. However, since the light source 1 is not an ideal point light source but has a finite size, the condensed light flux includes many light components that are not parallel to the axis of symmetry O of the paraboloid.

  This condensed light flux enters the first fly-eye lens 3a. The first fly-eye lens 3a is configured by combining a plurality of lenses having a positive refractive power having a rectangular outer shape in a matrix shape, and divides an incident light beam into a plurality of light beams corresponding to the respective lenses. , Concentrate. The plurality of divided light beams pass through the second fly-eye lens 3b, and form a plurality of light source images in the vicinity of the polarization conversion element 4 in a matrix.

  The polarization conversion element 4 includes a polarization separation surface, a reflection surface, and a half-wave plate (not shown). A plurality of light beams condensed in a matrix in the vicinity of the polarization conversion element 4 enter a polarization separation surface corresponding to the column, and are divided into a P-polarized component light beam that passes through the polarization separation surface and a reflected S-polarized component light beam. Is done. Further, the light beam of the S polarization component reflected by the polarization separation surface is reflected by the reflection surface and is emitted in the same direction as the P polarization component. On the other hand, the P-polarized light beam transmitted through the polarization splitting surface is transmitted through the half-wave plate and converted into the same polarized light as the S-polarized light, and the polarization direction (in the figure, indicates S-polarized light) is aligned. Emitted as a luminous flux. The plurality of light beams that have undergone polarization conversion by the polarization conversion element 4 reach the condensing optical system 5 as divergent light beams.

  The light beam enters the dichroic mirror 6 from the same direction as the light beam emission direction from the reflector 2. The dichroic mirror 6 has characteristics as indicated by a solid line in FIG. That is, B and G light (430 to 570 nm) is transmitted, and R light (580 to 650 nm) is reflected. Here, the transmittance of the S polarization component of R is set to 1% or less at 610 nm, which is the center wavelength of the wavelength range of R, thereby preventing the color purity of the other two color lights from being lowered. Yes.

  In FIG. 1, S-polarized light (•) emitted from the polarization conversion element 4 also enters the dichroic mirror 6 as S-polarized light (•).

  Here, in this embodiment, since the dichroic mirror 6 is provided between the second condenser lens 5b and the field lens 5c (5c ′), the light beam acting on the dichroic mirror 6 is not telecentric. . For this reason, the dichroic mirror 6 has a structure in which the film thickness gradually increases in the direction from A to B in the figure, and corrects the change in characteristics due to the incident angle.

  In the R optical path, the light reflected by the dichroic mirror 6 passes through the field lens 5 c ′ and enters the color filter 7. The color filter 7 has a characteristic as indicated by a dotted line in FIG. 2, and is a dichroic filter that reflects yellow color light (570 to 590 nm) in an intermediate wavelength region between G and R. Thereby, the yellow light component is removed. If there are many yellow components in red light, red will become orange. Therefore, it is desirable to remove yellow light in terms of color reproduction.

  In this embodiment, the color filter 7 is provided separately from the field lens 5c '. However, a color filter may be provided on the lens surface of the field lens 5c'.

  The red light thus color-adjusted enters the first polarizing beam splitter 10a as S-polarized light (·), is reflected by the polarization separation surface thereof, and reaches the R reflective liquid crystal display element 11r.

  Of the R light that has been image-modulated and reflected by the reflective liquid crystal display element 11r for R, the S-polarized light component (•) is reflected again by the polarization separation surface, returned to the light source side, and removed from the projection light. On the other hand, the P-polarized light component (|) of the R reflected light passes through the polarization separation surface and becomes projection light.

  The red light transmitted through the first polarizing beam splitter 10a is rotated by 90 degrees in the polarization direction by the half-wave plate 9, and is incident on the third polarizing beam splitter 10c as S-polarized light (•). . Then, this light is reflected by the polarization separation surface of the third polarization beam splitter 10 c and reaches the projection lens 13.

  The G and B lights that have passed through the dichroic mirror 6 pass through the field lens 5 c and enter the polarizing plate 14. The polarizing plate 14 has a characteristic of allowing the dichroic mirror 6 to transmit the polarization component that is S-polarized light and reflecting the polarization component that is P-polarized light. The light (·) whose polarization components are more aligned by the polarizing plate 14 is incident on the first color-selective retardation plate 8a. The first color-selective phase difference plate 8a has a function of rotating the polarization direction of the G light by 90 degrees, so that the G light becomes P-polarized light (|) and the B light becomes S-polarized light (·), respectively. The light enters the second polarizing beam splitter 10b.

  The B light is reflected by the polarization separation surface of the second polarizing beam splitter 10b, and is image-modulated and reflected by the B reflective liquid crystal display element 11b. The S-polarized component (•) of the reflected light of B is reflected again by the polarization separation surface, returned to the light source side, and removed from the projection light. On the other hand, the P-polarized light component (|) of the reflected light of B is transmitted through the polarization separation surface and becomes projection light.

  Similarly, the G light is transmitted through the polarization separation surface of the second polarization beam splitter 10b, and is image-modulated and reflected by the reflection liquid crystal display element 11g for G. The P-polarized component (|) of the G reflected light is transmitted again through the polarization separation surface, returned to the light source side, and removed from the projection light. On the other hand, the S-polarized component (•) of the reflected light of G is reflected by the polarization separation surface to become projection light. As a result, the B and G projection lights are combined into one light beam.

  The combined G and B projection light enters the second color-selective phase difference plate 28b. The second color-selective phase difference plate 8b is the same as the first color-selective phase difference plate 8a, and rotates only the polarization direction of G by 90 degrees. Then, the light is incident on the third polarizing beam splitter 10c. These G and B lights pass through the polarization separation surface of the third polarization beam splitter 10c and are combined with the R projection light.

  Here, the quarter wavelength plates 12g and 12b provided between the second polarizing beam splitter 10b and the reflective liquid crystal display elements 11g and 11b for G and B can rotate the direction of the slow axis. It has become. Thereby, it is possible to adjust the polarization state disturbance generated by the second polarizing beam splitter 10b and the reflective liquid crystal display elements 11g and 11b.

  In addition, the half-wave plate 9 provided on the incident side of the third polarizing beam splitter 10c can adjust the slow axis so that leakage of non-projection light in the third polarizing beam splitter 10c is minimized. It has become.

  An antireflection coat is applied to the boundary surface between each optical element and the air in this embodiment. In addition, an antireflection coating that is set so that the wavelength band in which the reflectance decreases most is in the vicinity of 550 nm is applied to the surface through which only the G light is transmitted. Further, an antireflection coat in which a wavelength band in which the reflectance decreases most is set in the vicinity of 610 nm is applied to a surface through which only R light is transmitted. In addition, an antireflection coat in which the wavelength band in which the reflectance is most reduced is set to the vicinity of 450 nm is provided on the surface through which only the B light is transmitted, and the reflectance is reduced on the surface through which the G light and the B light are transmitted. An anti-reflection coating having a wavelength band between 450 nm and 550 nm is applied.

  Here, each polarization beam splitter is a polarization beam puller using the same polarization separation film that decomposes the P-polarized component and the S-polarized component in the visible wavelength region (430 to 650 nm). However, the film characteristics may be set according to the wavelength region used in each optical path. For example, the first polarization beam splitter 10a in the R optical path uses a polarization separation film that decomposes the P polarization component and the S polarization component at 580 to 650 nm, and the second polarization beam splitter 10b in the B and G optical paths. For this, a polarization separation film that decomposes the P-polarized component and the S-polarized component at 430 to 595 nm is used. The third polarizing beam splitter 10c uses a polarization separation film that decomposes the P-polarized component and the S-polarized component at 430 to 650 nm.

In the above embodiment,
−2.5 <f2 / fc <−1 (1)
It is desirable to satisfy the following condition. fc is the focal length of the entire condensing optical system 5, that is, the focal length obtained by synthesizing the focal lengths of the first condenser lens 5a, the second condenser lens 5b, and the field lens 5c (5c ′). F2 is the focal length of the second condenser lens 5b.

  When f2 / fc is larger than the upper limit value of the expression (1), the focal lengths of the first condenser lens 5a and the second condenser lens 5b are increased, and the brightness in the illumination area on the reflective liquid crystal display element is increased. The uniformity of thickness will be reduced. Moreover, when f2 / fc is smaller than the lower limit value of the expression (1), the total length of the condensing optical system 5 becomes long, and the compactness is impaired.

  Therefore, by setting the value of f2 / fc so as to satisfy the expression (1), the brightness uniformity in the illumination area on the reflective liquid crystal display elements 11r, 11g, and 11b is sufficiently ensured. The size of the optical system (illumination optical system) from the light source (1, 2) to the first and second polarizing beam splitters 10a, 10b can be reduced.

  Hereinafter, numerical examples in which specific numerical data is applied to the first embodiment will be described. Here, an example in which the screen size of the reflective liquid crystal display element is 0.5 ″ (inch) is shown.

(Numerical example 1)
Table 1 shows the lens data of the first and second fly-eye lenses 3a and 3b shown in FIG. 3, and Table 2 shows the lens data of the condensing optical system 5 shown in FIG. In Tables 1 and 2, r represents the radius of curvature (mm), d represents the surface spacing (mm), and n represents the refractive index of the material.

  Surfaces 1 and 2 are surfaces of the first fly-eye lens 3a, and surfaces 3 to 4 are surfaces of the second fly-eye lens 3b.

  Surfaces 1 and 2 are surfaces of the first condenser lens 5a, surfaces 3 to 4 are surfaces of the second condenser lens 5b, and surfaces 5 to 6 are surfaces of the field lens 5c (5c ').

Here, in this numerical example, the focal lengths of the entire system of the condensing optical system 5, that is, the focal lengths of the first condenser lens 5a, the second condenser lens 5b, and the field lens 5c (5c ′) are synthesized. The focal length fc is
fc = 82.4mm
The focal length ff2 of the second fly-eye lens 3b is
ff2 = 29.5mm
It is.

Therefore,
β = fc / ff2 = 2.793
It becomes. The condensing optical system 5 forms a rectangular image of the first fly-eye lens 3a at the magnification β.

  Since the screen size of 0.5 ″ is 10.2 × 7.6 mm, the uniformly illuminated area is 12.2 × 9.6 mm. In this case, the individual lenses of the first fly-eye lens 3a May be a rectangle of 4.35 × 3.44 mm.

The focal length f2 of the second condenser lens 5b is
f2 = -53.6 mm
It is. For this reason,
β = f2 / fc = −1.54
It is. That is, the expression (1) is satisfied.

Here, the combined focal length fc23 of the second condenser lens 5b and the field lens 5c (5c ′) is fc23 = 82.4 mm.
So
fc / fc23 = 1
Thus, in the optical path from the field lens 5c (5c ′) to the reflective liquid crystal display elements 11g, 11b, and 11r, the light condensed on the reflective liquid crystal display element is relative to the optical axis of the condensing optical system 5. It becomes almost telecentric.

  FIG. 5 shows the configuration of a display optical system that is Embodiment 2 of the present invention. In this figure, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

  Reference numeral 23a denotes a first fly-eye lens in which a plurality of rectangular lenses are arranged in a matrix, and reference numeral 23b denotes a second fly-eye lens comprising a plurality of lenses corresponding to the individual lenses of the first fly-eye lens. Reference numeral 24 denotes a polarization conversion element. Reference numeral 25a denotes a first condenser lens (first lens), reference numeral 25b denotes a second condenser lens (second lens), and reference numerals 25c and 25c 'denote field lenses (third lenses). A condensing optical system 25 includes the first condenser lens 25a, the second condenser lens 25b, and the field lenses 25c and 25c '. The first condenser lens 25a has a positive refractive power, and the second condenser lens 25b has a negative refractive power. Further, the field lenses 25c and 25c 'have a positive refractive power.

  The present embodiment is a display optical system suitable for a screen size of 0.5 "as in the first embodiment. The difference from the first embodiment is that the rectangular shape of the fly-eye lenses 23a and 23b is 3.1 ×. The pitch of the polarization conversion element 24 is also reduced in accordance with the size of the fly-eye lens because it is 2.5 mm, where the lens data of the fly-eye lenses 23a and 23b is the same as in the first embodiment.

  Also in this embodiment, it is desirable to satisfy the above expression (1).

Hereinafter, numerical examples corresponding to the second embodiment will be described.
(Numerical example 2)
Table 3 shows lens data of the condensing optical system 25 shown in FIG. In Table 3, r represents the radius of curvature (mm), d represents the surface spacing (mm), and n represents the refractive index of the material.

  Surfaces 1 and 2 are surfaces of the first condenser lens 25a, surfaces 3 to 4 are surfaces of the second condenser lens 25b, and surfaces 5 to 6 are surfaces of the field lens 25c (25c ').

Here, the focal length fc of the entire condensing optical system 5 is fc = 14.9 mm.
And the magnification β is
β = fc / ff2 = 3.895
It becomes. The condensing optical system 25 forms a rectangular image of the first fly-eye lens 23a at this magnification β.

The focal length f2 of the second condenser lens 25b is
f2 = -52.9 mm
And the magnification β is
β = f2 / fc = -2.14
It becomes. That is, the expression (1) is satisfied.

Here, the combined focal length fc23 of the second condenser lens 25b and the field lens 25c (25c ′) is:
fc23 = 12.8mm
It is. For this reason,
fc / fc23 = 0.92
It becomes.

  The illumination optical system to which the present invention is applied is not limited to the configuration described in each of the above embodiments, and the present invention can be applied to an illumination optical system in which each embodiment is appropriately changed. .

1 is a diagram illustrating a configuration of a display optical system that is Embodiment 1 of the present invention. FIG. FIG. 3 is a characteristic diagram of a dichroic mirror and a color filter used in the first embodiment. FIG. 3 is a diagram illustrating a fly-eye lens used in Example 1. FIG. 3 is a diagram illustrating a condensing optical system used in Example 1. FIG. 5 is a diagram illustrating a configuration of a display optical system that is Embodiment 2 of the present invention. FIG. 5 is a diagram illustrating a condensing optical system used in Example 2. The figure explaining the conventional display optical system. (a), (b) is a figure which shows the polarization separation characteristic of a polarization beam splitter, respectively.

DESCRIPTION OF SYMBOLS 1 Discharge lamp 2 Reflector 3a 1st fly eye lens 3b 2nd fly eye lens 4 Polarization conversion element 5a 1st condenser lens 5b 2nd condenser lens 5c, 5c 'Field lens 6 Dichroic mirror 7 Color filter 8a, 8b Color selective phase difference plate 9a, 9b 1/2 wavelength plate 10a, 10b, 10c Polarization beam splitter 11r, 11g, 11b Reflective liquid crystal display element 12r, 12g, 12b 1/4 wavelength plate 13 Projection lens

Claims (12)

A light beam dividing means for dividing a light beam from a light source into a plurality of light beams;
A color separation optical system that color-separates the light beam from the light beam splitting unit and guides it to a plurality of image forming elements,
The color separation optical system includes a dichroic mirror and a polarization separation element on which a light beam from the dichroic mirror is incident, and a condensing optical system is provided between the light beam splitting unit and the polarization separation element,
The condensing optical system is disposed between the light beam splitting unit and the dichroic mirror, between the first and second lenses disposed in order from the light source side, and between the dichroic mirror and the polarization separation element. And an illuminated third lens.   The illumination optical system according to claim 1, wherein the image forming element is a reflective image forming element. The illumination optical system according to claim 1, wherein the following condition is satisfied.
−2.5 <f2 / fc <−1
Here, fc is the focal length of the entire focusing optical system, and f2 is the focal length of the second lens.   The illumination optical system according to any one of claims 1 to 3, wherein an emission direction of the light beam from the light source and an incident direction of the light beam to the dichroic mirror are substantially the same direction. A plurality of image forming elements;
An image display apparatus comprising: the illumination optical system according to claim 1, wherein the plurality of image forming elements are illuminated with light from the light source. A plurality of image forming elements;
The illumination optical system according to any one of claims 1 to 4, wherein the plurality of image forming elements are illuminated with light from the light source;
A color synthesis optical system for synthesizing light from the plurality of image forming elements;
An image display apparatus comprising: a projection optical system that projects a light beam synthesized by the color synthesis optical system onto a projection surface.   The display optical system according to claim 5, wherein the color synthesis optical system includes at least two polarization separation elements. An illumination optical system including a dichroic mirror and a polarization separation element, and having a color separation optical system that separates a light beam from a light source and guides the light to a plurality of image forming elements,
An illumination optical system comprising a first optical system having refractive power between the dichroic mirror and the polarization separation element. Between the light source and the dichroic mirror, there is a light beam dividing means for dividing the light beam from the light source into a plurality of parts,
9. The illumination optical system according to claim 8, further comprising a second optical system having a refractive power between the light beam splitting unit and the dichroic mirror. An optical system including the first optical system and the second optical system is a condensing optical system,
When the second optical system has first and second lenses in order from the light source side,
−2.5 <f2 / fc <−1
The illumination optical system according to claim 9, wherein the following condition is satisfied.
Here, fc is the focal length of the entire focusing optical system, and f2 is the focal length of the second lens. A plurality of image forming elements;
11. An image display apparatus comprising: the illumination optical system according to claim 8 illuminating the plurality of image forming elements with light from the light source. A plurality of image forming elements;
The illumination optical system according to any one of claims 8 to 10, wherein the plurality of image forming elements are illuminated with light from the light source;
A color synthesis optical system for synthesizing light from the plurality of image forming elements;
An image display apparatus comprising: a projection optical system that projects a light beam synthesized by the color synthesis optical system onto a projection surface.

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