JP2015210488A - Illumination optical system and image display device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination optical system capable of illuminating a target surface with uniform illuminance using a smaller polarization conversion element.SOLUTION: An illumination optical system includes a PBS 11 for directing S-polarized light of a light ray from a light source 1 to a direction different from that of P-polarized light, and a 1/2 wavelength plate 12 for aligning polarization directions of the P-polarized light and S-polarized light having different polarization directions. The system also includes a collimator lens 3 to which the light ray coming out from the PBS 11 and 1/2 wavelength plate 12 enter, a fly-eye lens 4, and a fly-eye lens 5. The light ray traveling from the light source 1 to the PBS 11 is a converging light ray, and the collimator lens 3 is located between the PBS 11 and the fly-eye lens 4.

Description

  The present invention relates to an illumination optical system and an image display apparatus such as a projector using the illumination optical system.

  In recent years, projectors using liquid crystal panels (liquid crystal projectors) have been developed. As a liquid crystal projector, there is a demand for a projector capable of projecting an image having a bright, high contrast, and almost uniform brightness throughout.

  Japanese Patent Application Laid-Open No. H10-228707 discloses an illumination optical system that allows polarized light aligned in a predetermined direction to enter a liquid crystal panel in order to project a high-contrast image.

  In Patent Document 1, a substantially parallel light beam is made incident on a polarization conversion element in which a prism-type PBS (polarization beam splitter), a prism mirror, and a half-wave plate are integrated, and a light beam aligned in a predetermined polarization direction. A technique for emitting light is disclosed.

JP 2004-053641 A

  In general, liquid crystal projectors are required not only to project high-quality images, but also to be smaller.

  However, in the polarization conversion element described in Patent Document 1, it is necessary to make the polarization conversion element the same size as the fly-eye lens in order to allow a substantially parallel light beam to enter the fly-eye lens. It is difficult to reduce the size.

  Accordingly, an object of the present invention is to provide an illumination optical system capable of illuminating a surface to be illuminated with uniform illuminance with a smaller polarization conversion element.

In order to achieve the above object, the illumination optical system of the present invention comprises:
A polarizing element that guides a light beam having a second polarization direction different from the light beam in the first polarization direction out of the light beam from the light source in a direction different from the light beam in the first polarization direction;
A first phase plate that aligns the polarization directions of the light beams of the first polarization direction and the light beams of the second polarization direction, the polarization directions of which are different from each other;
A positive lens on which light beams emitted from the polarizing element and the first phase plate are incident;
A first lens array having a plurality of lens cells for dividing a light beam emitted from the positive lens into a plurality of light beams;
A second lens array having a plurality of lens cells corresponding to the plurality of lens cells of the first lens array,
The light flux from the light source toward the polarizing element is a convergent light flux,
The positive lens is provided between the polarizing element and the first lens array.

  ADVANTAGE OF THE INVENTION According to this invention, the illumination optical system which can illuminate a to-be-illuminated surface with uniform illumination intensity with a smaller polarization conversion element can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory diagram of an image display device in which a light source device shown in an embodiment of the present invention can be mounted. 1 shows an illumination optical system according to Example 1 of the present invention. The structure of the polarization conversion element 2 in Example 1 of this invention. Illumination optical system according to Example 2 of the present invention. The structure of the polarization conversion element 2 in Example 2 of this invention. Illumination optical system according to Example 3 of the present invention. The structure of the polarization conversion element 2 in Example 3 of this invention.

  Preferred embodiments of the present invention will be illustratively described below with reference to the drawings. However, the shapes of components described in this embodiment and their relative arrangements should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions. In other words, the shape of the component parts and the like are not stipulated to limit the scope of the present invention to the following embodiments.

[Description of Image Display Device]
FIG. 1 is a diagram for explaining the configuration of an image display apparatus M equipped with an illumination optical system shown in an embodiment of the present invention described later.

  The light beam emitted from the arc tube 100 in all directions is emitted as a substantially parallel light beam by the parabolic mirror 200 and enters the illumination optical system L. Of course, it does not have to be a completely parallel light beam, and it may be slightly diverging or converging as long as it can be used.

  The illumination optical system L is an illumination optical system shown in an example of the present invention described later.

  The dichroic mirror 700 has a characteristic of reflecting B (blue) and R (red) color light and transmitting G (green) color light.

  The PBS (polarization beam splitter) 800 guides the light beam in the P polarization direction out of the G color light in a direction different from the light beam in the S polarization direction, which is different from the light beam in the P polarization direction. Specifically, the PBS 800 is a PBS that transmits P-polarized light and reflects S-polarized light.

  900 (900R, 900G, 900B) are a liquid crystal panel for R color light, a liquid crystal panel for G color light, and a liquid crystal panel for B color light, respectively. The liquid crystal panel 900 is a light modulation element that modulates color light and emits modulated light. In this embodiment, the liquid crystal panel 900 is a reflective liquid crystal element.

  The quarter-wave plates 1000 (1000R, 1000G, and 1000B) are a quarter-wave plate for R color light, a quarter-wave plate for G color light, and a quarter-wave plate for B color light, respectively. .

  Reference numeral 1100 denotes an incident-side polarizing plate that transmits P-polarized light, and 1200 denotes a color-selective phase difference plate that converts the polarization direction of R color light by 90 degrees and does not convert the polarization direction of B color light.

  The PBS 1300 is a PBS (first polarizing element) that transmits P-polarized light and reflects S-polarized light, and has a polarization separation surface 1300a.

  Reference numeral 1400 denotes an exit side polarizing plate for G color light that transmits S-polarized light.

  The combining prism 1700 (light combining element) functions as a dichroic mirror that transmits B color light and reflects G color light with respect to B and G color light. On the other hand, for R color light, it acts as PBS that transmits P-polarized light and reflects S-polarized light. That is, the combining prism 1700 combines the B modulated light, the R modulated light, and the G modulated light.

  A color separation / synthesis system C is configured by the synthesis prism 1700 from the dichroic mirror 700 described above.

  Reference numeral 1800 denotes a projection lens optical system, and the illumination optical system L, the color separation / synthesis optical system C, and the projection lens optical system 1800 constitute an image display optical system.

  The above is the configuration of the image display apparatus M. Next, the optical action after passing through the illumination optical system L will be described. First, the G optical path will be described.

  The G color light transmitted through the dichroic mirror 700 enters the PBS 800, and P-polarized light is transmitted through the polarization splitting surface to reach the liquid crystal panel 900G. In the liquid crystal panel 900G, the G color light is image-modulated and reflected. The P-polarized component of the image-modulated G reflected light is again transmitted through the polarization separation surface of the PBS 800, returned to the light source side, and removed from the projection light.

  On the other hand, the S-polarized light component of the G-modulated reflected light that has undergone image modulation is reflected by the polarization separation surface of the PBS 800, passes through the exit-side polarizing plate 1400 that transmits S-polarized light, and travels toward the synthesis prism 1700 as projection light.

  At this time, in the black display state in which all polarization components are converted to P-polarized light, the fast axis or slow axis of the quarter wave plate 1000G is set so that the optical axis of the incident light to the PBS 800 and the reflected light Adjustment is performed in a direction substantially perpendicular to the plane including the optical axis. The quarter wavelength plate 1000 is provided between the PBS 800 and the liquid crystal panel 900G. Thereby, the influence of the disorder of the polarization state which generate | occur | produces in PBS800 and the liquid crystal panel 900G can be suppressed. That is, the quarter wavelength plate 1000G is a phase plate that converts the polarization direction of the G color light emitted from the PBS 800.

  On the other hand, the R and B color lights reflected by the dichroic mirror 700 are incident on the incident-side polarizing plate 1100 that transmits the P-polarized light. The R and B color lights are emitted from the incident-side polarizing plate 1100 and then enter the color-selective retardation plate 1200. The color-selective phase difference plate 1200 has an effect of rotating the polarization direction of only the R color light by 90 degrees, so that the R color light is incident on the PBS 13 as S-polarized light and the B color light as P-polarized light.

  The R color light incident on the PBS 1300 as S-polarized light is reflected by the polarization separation surface of the PBS 1300 and reaches the liquid crystal panel 900R. The B color light incident on the PBS 1300 as P-polarized light passes through the polarization separation surface of the PBS 1300 and reaches the liquid crystal panel 9B.

  The R color light incident on the liquid crystal panel 900R is image-modulated and reflected. The S-polarized light component of the image-modulated R reflected light is reflected again by the polarization separation surface of the PBS 1300, returned to the light source side, and removed from the projection light. On the other hand, the P-polarized component of the image-modulated R reflected light passes through the polarization separation surface of the PBS 1300 and travels to the combining prism 1700 as projection light.

  That is, the PBS 1300 is a polarizing element that guides one of the B color light and the R color light in a direction different from that of the other color light.

  Further, the B color light transmitted through the PBS 1300 enters the liquid crystal panel 9B, and is image-modulated and reflected. The P-polarized component of the image-modulated B reflected light is again transmitted through the polarization separation surface of the PBS 1300 and returned to the light source side, and is removed from the projection light. On the other hand, the S-polarized component of the image-modulated B reflected light is reflected by the polarization separation surface of the PBS 1300 and travels to the combining prism 1700 as projection light.

  At this time, by adjusting the fast axis or slow axis of the quarter-wave plates 1000R and 1000B in the same manner as in the case of G color light, the black display of each of the R and B color lights can be adjusted. it can. The quarter-wave plates 1000R and 1000B are provided between the PBS 1300 and the liquid crystal panels 900R and 900B.

  That is, the quarter wavelength plate 1000B converts the polarization direction of the B color light emitted from the PBS 1300, and the quarter wavelength plate 1000R is a phase plate that converts the polarization direction of the R color light emitted from the PBS 1300.

  The R and B color lights that are combined into one light flux and emitted from the PBS 1300 enter the synthesis prism 1700. The R and B color lights that enter the synthesis prism 1700 pass through the synthesis prism 1700 and are combined with the G color light. Then, the projection lens optical system 1800 is reached.

  The combined R, G, and B projection light is enlarged and projected onto a projection surface such as a screen by the projection lens optical system 1800.

  The optical path described above is when the liquid crystal panel 9 performs white display. An optical path when the liquid crystal panel 900 performs black display will be described below.

  The P-polarized light of the G color light transmitted through the dichroic mirror 700 enters the PBS 800, passes through the polarization separation surface, and reaches the G reflective liquid crystal display element 900G. When the liquid crystal panel 900G performs black display, the G color light is reflected without being image-modulated. Therefore, since the G color light remains P-polarized light even after being reflected by the liquid crystal panel 900G, it passes through the polarization separation surface of the PBS 800 again, returns to the light source side, and is removed from the projection light.

  Next, the optical paths of the R and B color lights will be described.

  The R and B color lights reflected by the dichroic mirror 700 are incident on the incident-side polarizing plate 1100 that transmits the P-polarized light. The R and B color lights are emitted from the incident-side polarizing plate 1100 and then enter the color-selective retardation plate 1200. The color-selective phase difference plate 1200 has an action of rotating only the R color light by 90 degrees in the polarization direction, whereby the R color light is incident on the PBS 1300 as S-polarized light and the B color light is incident on the PBS 1300 as S-polarized light. The R color light incident on the PBS 1300 as S-polarized light is reflected by the polarization separation surface of the PBS 1300 and reaches the liquid crystal panel 900R.

  The B color light incident on the PBS 1300 as P-polarized light passes through the polarization separation surface of the PBS 1300 and reaches the liquid crystal panel 900B. Since the liquid crystal panel 900R displays black, the R color light incident on the liquid crystal panel 900R is reflected without image modulation. Therefore, even after being reflected by the liquid crystal panel 900R, the R color light remains S-polarized light, and is reflected again by the polarization separation surface of the PBS 1300, and is converted to P-polarized light by the color selective phase difference plate 1200. The R color light converted to P-polarized light again passes through the incident-side polarizing plate 1100 and returns to the light source side, and is removed from the projection light, resulting in black display.

  On the other hand, the B color light incident on the liquid crystal panel 900B is reflected without being image-modulated because the liquid crystal panel 900B displays black. Therefore, even after being reflected by the liquid crystal panel 900B, the B color light remains P-polarized light, so that it again passes through the polarization separation surface of the PBS 1300, passes through the incident-side polarizing plate 1100, and returns to the light source side to be projected light. Removed from.

  In this way, since the RGB color light is removed from the projection light, black display can be performed.

  Hereinafter, a configuration applicable to the illumination optical system L will be described.

  The illumination optical system shown in the embodiment of the present invention includes a PBS 11, a half-wave plate 12, a collimator lens 3, and a fly-eye lens group 45. Furthermore, the illumination optical system shown in the embodiment of the present invention may further include a mirror 13.

  The PBS 11 is a polarizing element that guides an S-polarized light beam having a polarization direction different from that of the P-polarized light beam in a direction different from that of the P-polarized light beam.

  The half-wave plate 12 is a first phase plate.

  The collimator lens 3 is a positive lens on which light beams emitted from the PBS 11 and the half-wave plate 12 enter.

  The fly-eye lens 4 is a first lens array having a plurality of lens cells that divide the light beam emitted from the collimator lens 3 into a plurality of light beams.

  The fly-eye lens 5 is a second lens array having a plurality of lens cells corresponding to the plurality of lens cells of the fly-eye lens 4.

  The fly-eye lens 45 is a lens array unit that divides the light beam emitted from the collimator lens 3 into a plurality of light beams.

  The light flux from the light source 1 is a convergent light flux, and the plurality of light rays included in the light flux from the light source 1 proceed so as to reduce the distance to each other as they approach the PBS 13.

  The collimator lens 3 is provided between the PBS 11 and the fly eye lens 4.

  Furthermore, the illumination optical system shown in some embodiments of the present invention further includes a mirror 13 that converts the traveling direction of the light beam emitted from the half-wave plate 12.

  The specific configuration of the illumination optical system shown in the embodiments of the present invention will be described in the following embodiments.

[First embodiment]
FIG. 2 is a diagram illustrating the configuration of the illumination optical system shown in the first embodiment of the present invention. A configuration for illuminating the liquid crystal panel 7 with the light flux from the light source 1 will be described with reference to FIG.

  The illumination optical system shown in the present embodiment is an illumination optical system for illuminating the liquid crystal panel 7 with a light beam from the light source 1. Image light, which is light modulated by the liquid crystal panel 7, is guided to a projection lens (not shown) via a polarization beam splitter or polarizing plate (not shown) and projected onto a projection surface such as a screen.

  In this embodiment, the optical axis of the light beam from the light source 1 is the X axis, the optical axis of the collimator lens 3 orthogonal to the X axis is the Z axis, and the X axis and the axis orthogonal to the Z axis are the Y axis. Furthermore, the direction parallel to the Z axis is defined as the optical axis direction and the traveling direction of the light flux.

  The light source 1 is a lamp composed of an arc tube 11 which is a high-pressure mercury discharge tube and an elliptical mirror 12, and the lamp emits a light beam including S-polarized light and P-polarized light. The elliptical mirror 12 converts the light beam emitted radially from the arc tube 11 into a light beam that shortens the distance to the polarization conversion element 2 and condenses it in the vicinity of the half-wave plate 12.

  The configuration of the polarization conversion element 2 will be described with reference to FIG. The polarization conversion element 2 includes a PBS 11 that is a prism type PBS, a half-wave plate 12, and a mirror 13 that is a prism mirror.

  Of the luminous flux from the light source 1 that has entered the PBS 11, S-polarized light is reflected by the polarization separation surface 11 a of the PBS 11 and enters the collimator lens 3. On the other hand, of the light flux from the light source 1 that has entered the PBS 11, P-polarized light passes through the polarization separation surface 11 a and enters the half-wave plate 12. Here, the P-polarized light is linearly polarized light that vibrates in the main plane when the plane formed by the normal line of the polarization separation surface 11a and the optical axis in FIG. 2 is the main plane. Furthermore, S-polarized light is linearly polarized light that vibrates perpendicularly to the main plane.

  The P-polarized light incident on the half-wave plate 12 is converted to S-polarized light by the half-wave plate 12, reflected by the reflecting surface 13 a of the prism mirror 13, and incident on the collimator lens 3.

  The light beam incident on the collimator lens 3 is collimated by the collimator lens 3 and enters the fly-eye lens 4. The light beam incident on the fly-eye lens 4 is divided into a plurality of divided light beams, condensed near the lens cell of the fly-eye lens 5, and incident on the condenser lens 6. Here, as a matter of course, it is not necessary that the light beam is completely collected at one point, and it is sufficient that the light beam is almost collected within a practical range. Similarly, the lens cell vicinity does not have to be completely on the lens cell, and a range that can be practically used may be the lens cell vicinity.

  A plurality of split light beams emitted from the condenser lens 6 are superimposed on the liquid crystal panel 7. Thereby, the liquid crystal panel 7 is illuminated by the illumination light beam having a uniform distribution.

  The above is the configuration for the light flux from the light source 1 to illuminate the liquid crystal panel 7. By configuring the illumination optical system as shown in this embodiment, it is possible to provide an illumination optical system capable of illuminating the illuminated surface with uniform illuminance with a smaller polarization conversion element.

  As described above, the light modulated and reflected by the liquid crystal panel 7 is guided to the projection lens via the polarization beam splitter (not shown). In the present embodiment, only one liquid crystal panel 7 is shown, but in an actual general projector, three liquid crystal panels corresponding to R, G, and B are provided. Such a polarization beam splitter is a part of a so-called color separation / synthesis optical system that guides R, G, and B color illumination light to these three liquid crystal panels and synthesizes each color image light from the three liquid crystal panels. Configure.

  The embodiment of the present invention has the following configuration in order to make the above-described effect stronger or obtain other effects. However, the present invention is not limited to an illumination optical system having all the configurations described below.

  By arranging the longitudinal direction of the liquid crystal panel 7 in the x-axis direction of FIG. 2, it is possible to further increase the illumination efficiency. The lens cell of the first fly-eye lens 4 is conjugated with the liquid crystal panel. For this reason, when the longitudinal direction of the liquid crystal panel 7 is arranged in the x-axis direction, it is necessary to increase the size of the lens cell of the first fly-eye lens 4 in the x-axis direction. Similarly, since the size of the lens cell of the second fly-eye lens 5 is also increased, the luminous flux that can be captured by the lens cell of the second fly-eye lens 5 is increased, and the illumination efficiency can be improved.

  Further preferable conditions will be described.

  In the configuration shown in this embodiment, a light beam including a light beam having an incident angle of 45 ± 20 ° with respect to the polarization separation surface of the PBS 11 enters the PBS 11. On the other hand, the incident angle at which the polarization separation surface of the PBS 11 can perform polarization separation most efficiently is 45 °. For this reason, in order to obtain high polarization separation performance, it is desirable that the light incident on the polarization separation surface be about 45 ± 10 ° by using a glass material having a high refractive index.

At this time, the desirable refractive index n is
n> 1.8
And more preferably
n> 2.0
It is.

  Further preferable conditions will be described. In the embodiment of the present invention, since the light flux from the lamp 1 is condensed on the half-wave plate, it is desirable to use a highly durable inorganic material such as quartz or sapphire for the half-wave plate 12. .

  In addition, since the light density in the PBS 11 is high because the light is condensed on the half-wave plate 12, the PBS 11 becomes high in temperature, and photoelasticity is generated due to thermal stress, which may reduce the polarization conversion efficiency. For this reason, it is desirable that the absorption coefficient is low and the photoelastic constant is low in the visible light region.

  Therefore, the photoelastic constant of the half-wave plate 12 is β, and the internal transmittance for incident light with a wavelength of 460 nm when the half-wave plate 12 is 10 mm thick is T.

At this time,
β <1.0
T> 0.95
It is desirable to satisfy the following conditions.

  By satisfying this condition, it is possible to suppress the occurrence of photoelasticity due to the above-described thermal stress and decrease in polarization conversion efficiency.

  Further preferable conditions will be described. In the present embodiment, the illumination efficiency can be further improved by bringing the two light source images formed on the lens cell of the fly-eye lens 5 closer to each other toward the center of the lens cell.

Therefore, an angle formed between a direction O2 // parallel to the optical axis O2 of the collimator lens 3 and the polarization separation surface 11a of the PBS 11 is defined as θ1. Furthermore, when the angle between the direction O2 // parallel to the optical axis O2 of the collimator lens 3 and the reflecting surface 13a of the prism mirror 13 is θ2,
46 ° <θ1 <50 ° 40 ° <θ2 <44 ° (1)
It is desirable to satisfy the following conditions.

  When both θ1 and θ2 are 45 °, the light beams emitted from the polarization separation surface 11a and the reflection surface 13a are parallel to the optical axis O2, so that two light source images are formed on the lens cell of the fly-eye lens 5 as described above. Form an image.

  On the other hand, when Expression (1) is satisfied, the light beams emitted from the polarization separation surface 11a and the reflection surface 13a proceed so as to approach the optical axis O2. For this reason, the illumination efficiency can be further improved by bringing the two light source images formed on the lens cell of the fly-eye lens 5 closer to each other toward the center of the lens cell.

  For the above reasons, it is preferable that the expression (1) is satisfied.

  In this embodiment, as an example, θ1 = 47 ° and θ2 = 43 °, which satisfy the above-described conditional expression. Of course, the embodiment of the present invention is not limited to the case of θ1 = 47 ° and θ2 = 43 °.

  Further preferable conditions will be described.

  The direction parallel to the optical axis of the collimator lens 3 is the z-axis direction, orthogonal to the z-axis direction, and the direction in which the polarization separation surface 11a of the PBS 11 and the reflection surface 13a of the mirror 13 face each other is the x-axis direction (vertical direction). A direction orthogonal to the z-axis direction and the x-axis direction is taken as a y-axis direction.

  The dimension in the x-axis direction between the polarization separation surface 11a and the reflecting surface 13a is a, the dimension in the x-axis direction of the lens cell of the second fly-eye lens 5 is b, and the focal length of the collimating lens 3 is f1, The focal length of the lens cell of the first fly-eye lens 4 is assumed to be f2.

At this time,
0.6 <(2 · a / b) × (f2 / f1) <0.95 (2)
It is desirable to satisfy the following conditional expression.

  Exceeding the upper limit of equation (2) means that a is relatively larger than b when f2 and f1 are fixed.

  In other words, it means that the light source images of the two split light beams formed in each lens cell of the second fly's eye lens 5 are separated. As a result, the luminous flux that enters the adjacent lens cell instead of the corresponding lens cell increases, which may reduce the illumination efficiency.

  On the other hand, below the lower limit of equation (2), when f2 and f1 are fixed, it means that a is relatively smaller than b. In this case, although the amount of the light beam that enters the adjacent lens cell is reduced, the light beam that can enter the first polarization beam splitter 2 is reduced, which may reduce the illumination efficiency.

  That is, when the expression (2) is satisfied, the amount of the light beam that can be incident on the first polarization beam splitter 2 is suppressed while suppressing an increase in the amount of the light beam that is incident on the adjacent lens cell instead of the corresponding lens cell. Reduction can be suppressed. As a result, a decrease in illumination efficiency can be suppressed.

  For the above reason, it is preferable that the expression (2) is satisfied.

  In this embodiment, a = 4.0 mm, b = 6.3 mm, f2 = 30 mm, f1 = 50 mm, (2 · a / b) × (f2 / f1) = 0.76, Expression (2) is satisfied. However, the embodiment of the present invention is not limited to the case of a = 4.0 mm, b = 6.3 mm, f2 = 30 mm, and f1 = 50 mm as long as the expression (2) is satisfied.

[Second Embodiment]
4 and 5 are diagrams illustrating the configuration of the illumination optical system shown in the second embodiment of the present invention. The difference between this embodiment and the first embodiment described above is that a wire grid type PBS 31 is used instead of the prism type PBS 11 and a plate type mirror 33 is used instead of the prism mirror 13.

  In the first embodiment described above, the light beam that has passed through the PBS 11 is condensed near the half-wave plate 12. On the other hand, in this embodiment, the light beam reflected by the PBS 31 is condensed near the half-wave plate 12.

  Here, the wire grid type PBS 31 has a structure (sub-wavelength grating structure) in which metal wires are arranged at an interval narrower than the wavelength of incident light. The wire grid type PBS 31 has a property of reflecting linearly polarized light that oscillates in parallel with the longitudinal direction of the metal wire and transmits linearly polarized light that oscillates in a direction orthogonal to the longitudinal direction of the metal wire.

  Of the luminous flux from the light source 1, PBS 31 transmits P-polarized light and reflects S-polarized light. The S-polarized light reflected from the wire grid surface 31 a is converted into P-polarized light by the half-wave plate 12 and reflected to the liquid crystal panel side by the reflecting surface 33 a of the plate-type mirror 33. Thereafter, the light beam from the light source 1 is guided to the liquid crystal panel 7 on the same principle as in the first embodiment.

  The more desirable conditions in this embodiment are the same as those in the first embodiment.

[Third embodiment]
6 and 7 are views for explaining the configuration of the illumination optical system shown in the third embodiment of the present invention. The difference between this embodiment and the first embodiment described above is that the shape of the prism type PBS 11 and the mirror 12 are not used. Although not shown, a condenser lens 6 and a liquid crystal panel 7 are provided behind the fly-eye lens 5 as in the first and second embodiments.

  FIG. 7 shows the configuration of the polarization conversion element 2. As shown in FIG. 7, the polarization conversion element 2 in this embodiment is composed of only the PBS 11 and the half-wave plate 12.

  The light beam from the light source 1 is guided to the PBS 11 by the action of the elliptical mirror 12 so as to be condensed near the polarization separation surface 11a of the PBS 11. Since the polarization separation surface 11a has a characteristic of transmitting P-polarized light and reflecting S-polarized light, the P-polarized light transmitted through the polarization separation surface 11a is guided to the exit surface 11b of the PBS 11. The S-polarized light reflected by the polarization separation surface 11a is converted to P-polarized light by the half-wave plate 12 and guided to the output surface 11b. The light beam guided to the exit surface 11b is refracted by the exit surface 11b, and becomes parallel to the optical axis of the collimator lens 3.

  In other words, the PBS 11 emits, as the light rays parallel to the optical axis of the collimator lens 3, the light ray R11 reflected by the polarization separation surface 11a and the light beam R12 transmitted through the polarization separation surface 11a among the principal rays of the light flux from the light source 1. It is a prism type PBS of the shape to be formed.

  With such a configuration, it is possible to make the optical path lengths of the light beam reflected by the polarization separation surface 11a and the light beam transmitted through the polarization separation surface 11a equal. Accordingly, the displacement of the light source image position formed on the second fly-eye lens 45 in the optical axis direction is reduced, so that the liquid crystal panel can be illuminated with high efficiency.

[Other Embodiments]
In the above-described embodiments, the configuration including the projection lens is exemplified as the configuration of the projection type display device in which the illumination optical system shown in the embodiments of the present invention can be mounted. However, the present invention is not limited to this. If it is a projection type display apparatus, the structure using a detachable projection lens may be used, for example.

  Moreover, in the figure which shows the Example mentioned above, although not shown in figure, the structure etc. which arrange | position suitably various optical elements, such as a mirror which bends the optical path from a light source, a heat ray cut filter, and a polarizing plate, may be sufficient.

  In the above-described embodiment, the configuration including one condenser lens is illustrated, but the present invention is not limited to this. As long as it is a condenser lens unit for superimposing the light beams from the plurality of lens cells of the second lens array on the surface to be illuminated, it may be configured to include, for example, two or more lenses. Note that the condenser lens unit including two or more lenses may be one in which two or more lenses are integrally attached to the illumination optical system, or one that is attached one by one.

  In addition, in some of the above-described embodiments, the configuration in which one half-wave plate is provided is illustrated, but the present invention is not limited to this. If the illumination optical system can illuminate the surface to be illuminated with uniform illuminance with a smaller polarization conversion element, for example, instead of providing one half-wave plate, two quarter-wave plates are provided. It may be configured to be provided.

  In addition, in some of the above-described embodiments, the configuration in which the light beam from the light source is condensed in the vicinity of the half-wave plate is illustrated, but the present invention is not limited to this. If the illumination optical system can illuminate the surface to be illuminated with uniform illumination with a smaller polarization conversion element, for example, between the polarization separation surface and the half-wave plate, or between the mirror and the half-wave A configuration in which the light beam from the light source is condensed between the plate and the like may be used. Further, for example, a configuration in which the light beam from the light source is condensed outside the polarization conversion element may be used.

3 Collimator lens (positive lens)
11, 31 PBS (polarizing element)
12 1/2 wavelength plate (first phase plate)
4 Fly eye lens (first lens array)
5 Fly eye lens (second lens array)

Claims (8)

A polarizing element that guides a light beam having a second polarization direction different from the light beam in the first polarization direction out of the light beam from the light source in a direction different from the light beam in the first polarization direction;
A first phase plate that aligns the polarization directions of the light beams of the first polarization direction and the light beams of the second polarization direction, the polarization directions of which are different from each other;
A positive lens on which light beams emitted from the polarizing element and the first phase plate are incident;
A first lens array having a plurality of lens cells for dividing a light beam emitted from the positive lens into a plurality of light beams;
A second lens array having a plurality of lens cells corresponding to the plurality of lens cells of the first lens array,
The light flux from the light source toward the polarizing element is a convergent light flux,
The illumination optical system, wherein the positive lens is provided between the polarizing element and the first lens array.   The illumination optical system according to claim 1, further comprising a mirror that converts a traveling direction of the light beam having the second polarization direction. An angle between a direction parallel to the optical axis of the positive lens and a polarization separation surface of the polarizing element is θ1,
When the angle formed between the direction parallel to the optical axis of the positive lens and the reflecting surface of the mirror is θ2,
46 ° <θ1 <50 °
40 ° <θ2 <44 °
The illumination optical system according to claim 2, wherein the following condition is satisfied. The polarizing element is a prism-type polarizing beam splitter,
When the refractive index of the prism type polarizing beam splitter is n,
n> 1.8
The illumination optical system according to claim 1, wherein the following condition is satisfied.   The illumination optical system according to any one of claims 2 to 4, wherein the polarizing element, the mirror, and the first phase plate are a polarization conversion element configured integrally. The direction perpendicular to the optical axis of the positive lens, and the direction in which the polarization separation surface of the polarizing element and the reflection surface of the mirror face each other is defined as a vertical direction,
The vertical distance between the polarization separation surface of the polarization element and the reflection surface of the mirror is a,
The vertical dimension of each of the plurality of lens cells included in the second lens array is b,
The focal length of the positive lens is f1,
When the focal length of each of the plurality of lens cells of the first lens array is f2,
0.6 <(2 · a / b) × (f2 / f1) <0.95
The illumination optical system according to claim 2, wherein the following condition is satisfied. A light source device;
The illumination optical system according to any one of claims 1 to 6,
A lighting device comprising: A light modulation element;
A lighting device according to claim 7;
An image display device comprising:

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