JP2013024971A - Polarization conversion element, lighting device, and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization conversion element capable of uniformly exiting light primarily consisting of one polarization component from an exit surface thereof.SOLUTION: A polarization conversion element 40A includes: a light incident surface S 41; a light exit surface S42 having a first area A1 and a second area A2; a polarization separating film 47 obliquely facing the first area A1; a reflection coating 48 for reflecting second polarization light reflected by the polarization separating film 47 towards the second area A2; and a retardation plate 43 that is provided in the first area A1 and converts first polarization light transmitting through the polarization separating film 47 into the second polarization light. The polarization conversion element further includes an optical film 44 for reducing the quantity of light exited from the second area A2 in an area along a boundary of the second area A2 with the first area A1.

Description

  The present invention relates to a polarization conversion element, an illumination device, and a projector.

  The liquid crystal projector modulates the light emitted from the illumination device according to image information by the liquid crystal device, and enlarges and projects the obtained image by the projection lens.

  In recent years, as such a liquid crystal projector, a very small projector (so-called pico projector) aimed at mounting on a mobile device such as a mobile phone or a digital camera has been developed.

  Here, in a small-sized projector, it is necessary to simplify the configuration of the power supply circuit and the optical system, or to reduce the size of these components.

  As such a miniaturized projector, for example, a projector having a light source device including a solid light source and a phosphor, a collimator lens unit, a polarization conversion element, a liquid crystal panel as a light modulation device, and a projection optical system is known. It has been.

  In this projector, a single-panel liquid crystal panel is used as the light modulation device, and the optical member such as an integrator optical system that is normally disposed between the light source and the polarization conversion element is omitted, so that the size can be reduced. (For example, refer to Patent Document 1).

JP 2010-66351 A

  By the way, in the projector described above, the light source device, the collimator lens unit, and the polarization conversion element constitute an illumination device that irradiates the liquid crystal panel, and the light source light collimated by the collimator lens unit is converted into a single light by the polarization conversion element. The liquid crystal panel is irradiated with the light that is converted into light composed of the polarized light component. Here, since the light source device is not a complete point light source, the emitted light cannot be completely collimated by the collimator lens unit. That is, the light L from the collimator lens unit includes light L1 traveling parallel to the illumination optical axis 200ax and light (oblique light) L2 traveling obliquely with respect to the illumination optical axis 200ax. ing.

  For this reason, in the conventional polarization conversion element, when light from the collimator lens unit is directly incident, a part of the oblique light is emitted from the polarization conversion element without being converted into linearly polarized light. There is a problem that unevenness in illuminance occurs on the light irradiation surface of the liquid crystal panel. Hereinafter, the mechanism of occurrence of the illuminance unevenness will be described by taking the polarization conversion element shown in FIG. 10 as an example.

  FIG. 10 is a schematic diagram illustrating an example of a general polarization conversion element.

  A polarization conversion element 200 shown in FIG. 10 converts light L incident from a collimator lens unit (not shown) into light composed of an S-polarized component. The polarization conversion element 200 includes an optical block 200A and an optical block 200B. The configuration of the optical block 200A is the same as the configuration of the optical block 200B. Both the optical block 200A and the optical block 200B are composed of the polarization beam splitter 201 including the polarization separation film 203 and the internal total reflection prism 202 including the total reflection film 204. Become. The optical block 200A and the optical block 200B are arranged symmetrically with respect to the illumination optical axis 200ax. Therefore, in the following description, only the optical block 200A will be described, and description regarding the optical block 200B will be omitted.

  Of the plurality of surfaces of the polarization conversion element 200, the surface on the side on which the light L emitted from the collimator lens unit is incident is referred to as a light incident surface S <b> 21 of the polarization conversion element 200. Among these, a surface facing the light incident surface of the polarization conversion element 200 is referred to as a light exit surface S22 of the polarization conversion element 200.

  Of the light exit surface S22 of the polarization conversion element 200, a region corresponding to the light exit surface of the polarization beam splitter 201 is referred to as a “first region B1”. In addition, the region corresponding to the light exit surface of the internal total reflection prism 202 in the light exit surface S22 of the polarization conversion element 200 is referred to as a “second region B2”.

  The first region B1 is provided with a phase difference plate 206 that converts a P-polarized component into an S-polarized component. A total reflection film 205 is provided in a region of the light incident surface S21 that faces the second region B2. A region where the total reflection film 205 is not provided in the light incident surface S <b> 21 constitutes a light guide port B <b> 3 through which the light L is introduced into the polarization conversion element 200.

  On the slope inside the polarizing beam splitter 201, the S-polarized component incident from the light guide B3 of the light incident surface S21 is reflected in a direction orthogonal to the illumination optical axis 200ax, and P incident from the light guide B3 is reflected. A polarization separation film 203 that transmits polarized light is provided. Further, a total reflection film 204 that reflects the S-polarized light component reflected by the polarization separation film 203 in a direction parallel to the illumination optical axis 200ax is provided on the inclined surface inside the internal total reflection prism 202.

  In such a polarization conversion element 200, the light L emitted from the collimator lens unit travels into the polarization conversion element 200 from the light guide opening B3 and is mainly incident on the polarization separation film 203. Of the light incident on the polarization separation film 203, the S-polarized component is reflected by the polarization separation film 203 and the total reflection film 204, and its optical path is translated from the polarization beam splitter 201 to the internal total reflection prism 202 side. The S-polarized component is emitted from the second region B2 as S-polarized light. On the other hand, the P-polarized component of the light incident on the polarization separation film 203 is transmitted through the polarization separation film 203. The P-polarized component transmitted through the polarization separation film 203 is converted into an S-polarized component by passing through the retardation plate 206, and is emitted from the first region B1. Therefore, in this polarization conversion element 200, the light L incident on the polarization separation film 203 from the light guide port B3 is emitted from the first region B1 and the second region B2 as an S-polarized component.

  However, the light L incident from the collimator lens unit includes oblique light L2 incident from an oblique direction with respect to the illumination optical axis 200ax. The oblique light L2 does not enter the polarization separation film 203, travels directly from the light guide port B3 to the second region B2, and is emitted from the second region B2.

  Thus, the oblique light L2 emitted from the vicinity of the boundary between the second region B2 and the first region B1 in the second region B2 passes through the polarization separation film 203, the retardation film 206, and the second total reflection film 204. Therefore, both the S-polarized light component and the P-polarized light component are included, and since the light is emitted from a region different from the region that should be emitted, the amount of light emitted from this region is larger than that of other regions. For this reason, when the light emitted from the polarization conversion element 200 is used as illumination light, line-shaped illuminance unevenness occurs due to the non-polarized oblique light L2.

  Here, if an optical component that enhances the parallelism of light is arranged between the collimator lens unit and the polarization conversion element 200, such a problem of uneven illuminance can be avoided. However, as described above, in a small projector, it is necessary to avoid adding other optical components as much as possible, and development of a configuration that can eliminate unevenness in illumination while reducing the size of the projector is required.

  The present invention has been made in view of such circumstances, and irradiates an illumination target with a polarization conversion element having high in-plane uniformity of intensity of emitted light and illumination light having high in-plane uniformity of intensity. An object of the present invention is to provide an illuminating device that can be used. Moreover, it aims at providing the projector excellent in display quality provided with such an illuminating device.

  The polarization conversion element of the present invention is disposed so as to face a light incident surface, a light exit surface having a first region and a second region adjacent to each other, and obliquely opposed to the first region. A polarization separation film that transmits the second polarized light in the second polarization state of the incident light to the first region and reflects the first polarized light in the first polarization state of the incident light; A reflective film that reflects the first polarized light reflected by the polarization separation film toward the second region; and a polarization state of the first polarized light that is provided in the second region. An optical element that is provided in a region along a boundary between the phase difference plate that converts the first polarization state to the second polarization state and the first region of the second region, and that reduces the amount of light emitted from the second region. And a film.

The light incident on the polarization conversion element from the collimator optical system includes light traveling in parallel to the illumination optical axis and light traveling in an oblique direction with respect to the illumination optical axis (oblique light).
Among these, a part of the oblique light from the collimator optical system is directly incident from the light incident surface in the vicinity of the boundary with the phase difference plate (first region) in the second region without passing through the polarization separation film. Since the oblique light incident near the boundary includes the first polarized light and the second polarized light, the amount of light emitted near the boundary becomes larger than that in other regions, and causes uneven illumination. It becomes.

  On the other hand, in the polarization conversion element of the present invention, an optical film that reduces the amount of light emitted from the second region is provided in a region along the boundary between the second region and the first region. Yes. Therefore, the amount of oblique light emitted from the vicinity of the boundary between the second region and the first region can be reduced. For this reason, the difference in the amount of emitted light between the vicinity of this boundary and other regions is reduced or eliminated, and the in-plane uniformity of the emitted light intensity on the light emitting surface can be increased.

  The polarization conversion element of the present invention is disposed so as to face a light incident surface, a light exit surface having a first region and a second region adjacent to each other, and obliquely opposed to the first region. A polarization separation film that transmits the second polarized light in the second polarization state of the incident light to the first region and reflects the first polarized light in the first polarization state of the incident light; A reflective film that reflects the first polarized light reflected by the polarization separation film toward the second region; and a polarization state of the first polarized light that is provided in the second region. An optical element that is provided in a region along a boundary between the phase difference plate that converts the first polarization state to the second polarization state and the first region of the second region, and that reduces the amount of light emitted from the second region. And a film.

The light incident on the polarization conversion element from the collimator optical system includes light traveling in parallel to the illumination optical axis and light traveling in an oblique direction with respect to the illumination optical axis (oblique light).
Among these, a part of the oblique light from the collimator optical system is directly incident from the light incident surface in the vicinity of the boundary with the phase difference plate (first region) in the second region without passing through the polarization separation film. Since the oblique light incident near the boundary includes the first polarized light and the second polarized light, the amount of light emitted near the boundary becomes larger than that in other regions, and causes uneven illumination. It becomes.

  On the other hand, in the polarization conversion element of the present invention, an optical film that reduces the amount of light emitted from the second region is provided in a region along the boundary between the second region and the first region. . Therefore, the amount of oblique light emitted from the vicinity of the boundary between the second region and the first region can be reduced. For this reason, the difference in the amount of emitted light between the vicinity of this boundary and other regions is reduced or eliminated, and the in-plane uniformity of the emitted light intensity on the light emitting surface can be increased.

  In the present invention, the optical film is preferably a polarizing plate that transmits the second polarized light and shields the first polarized light.

  According to this configuration, of the oblique light incident near the boundary between the second region and the first region, the second polarized light is transmitted through the polarizing plate, and the first polarized light is shielded by the polarizing plate. Therefore, the amount of oblique light emitted from the vicinity of the boundary can be reduced by at least the amount of the first polarized light shielded by the polarizing plate. For this reason, the difference in the amount of emitted light between the vicinity of this boundary and other regions is reduced or eliminated, and the in-plane uniformity of the emitted light intensity on the light emitting surface can be increased.

  In this invention, it is preferable that the said optical film has comprised the strip | belt shape extended in the direction orthogonal to the reflection direction of the light in the said polarization separation film.

  According to this configuration, since the planar shape of the optical film substantially coincides with the planar shape of the incident region of the oblique light incident near the boundary between the second region and the first region, the optical film is emitted from the vicinity of this boundary. It is possible to reliably reduce the amount of oblique light.

In the present invention, the width of the optical film is preferably in a range represented by the following formula.
L · tan θ−0.1 ≦ d ≦ L · tan θ + 0.1
d: Width of optical film (mm)
L: Thickness of polarization conversion element (mm)
θ: An angle formed between the traveling direction of light incident on the second region from the light incident surface without passing through the polarization separation film in the incident light and the principal ray axis of light emitted from the light exit surface

  According to this configuration, since the width of the optical film substantially coincides with the width of the incident region of the oblique light incident near the boundary between the second region and the first region, the oblique light emitted from the vicinity of the boundary. It is possible to reliably reduce the amount of light.

  An illumination device according to the present invention includes a solid-state light source device, a collimator lens unit that substantially collimates light emitted from the solid-state light source device, and a polarization conversion element on which light emitted from the collimator lens unit is incident. It is an illumination apparatus provided, Comprising: The said polarization conversion element is a polarization conversion element of this invention, It is characterized by the above-mentioned.

  For this reason, according to the illuminating device of this invention, it is possible to irradiate 2nd polarization | polarized-light light to illumination object with a small intensity | strength nonuniformity.

  In the present invention, the solid-state light source device is preferably a white light source having an excitation light source made of a light emitting diode or a semiconductor laser and a phosphor.

  According to this configuration, it is possible to reduce the size of the lighting device.

  The projector of the present invention includes an illumination device, a light modulation device that modulates illumination light from the illumination device according to image information, and a projection optical system that projects the modulated light from the light modulation device as a projection image. It is a projector, Comprising: The said illuminating device is an illuminating device of this invention, It is characterized by the above-mentioned.

  According to this configuration, since the illumination device can uniformly irradiate the light modulation device with light composed of one polarization component, it is possible to display a high-quality image with little unevenness in brightness. It becomes.

  In the present invention, the light modulation device is preferably a single-plate liquid crystal light modulation device.

  According to this configuration, it is possible to reduce the size of the projector.

FIG. 2 is a schematic diagram illustrating an optical system of the projector according to the first embodiment. It is a front view of the illuminating device and liquid crystal light modulation apparatus with which the projector shown in FIG. 1 is provided. It is sectional drawing of the solid light source device with which the projector shown in FIG. 1 is provided. It is typical sectional drawing of the polarization conversion element (polarization conversion element of Embodiment 1) with which the projector shown in FIG. 1 is provided. FIG. 3 is a plan view of the polarization conversion element according to Embodiment 1 viewed from the light exit surface side. 3 is a photograph showing an illumination image of light emitted from the polarization conversion element of Embodiment 1. FIG. It is a photograph which shows the illumination image of the light inject | emitted from the polarization conversion element which does not provide the S transmissive polarizing plate. 6 is a schematic cross-sectional view of a polarization conversion element according to Embodiment 2. FIG. 6 is a plan view of a polarization conversion element according to Embodiment 2 viewed from a light exit surface side. FIG. It is a typical sectional view showing a general polarization conversion element.

  Embodiments of the present invention will be described below with reference to the drawings. This embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, the scale, number, etc. in the actual structure are different.

<Embodiment 1>
Embodiment 1 of the polarization conversion element, illumination device, and projector of the present invention will be described.

(Projector configuration)
First, an example of a projector to which the polarization conversion element and the illumination device of the present embodiment are applied will be described.

  1 is a schematic diagram illustrating an optical system of a projector according to a first embodiment, FIG. 2 is a front view of an illumination device and a liquid crystal light modulation device provided in the projector illustrated in FIG. 1, and FIG. 3 is provided in the projector illustrated in FIG. It is sectional drawing of a solid light source device.

  As shown in FIG. 1, the projector 1000 according to the first embodiment includes an illumination device 100, a liquid crystal light modulation device 50, and a projection optical system 70, and the illumination device 100 is configured by the illumination device according to the first embodiment. Yes.

  The illumination device 100 includes a solid light source device 10, a collimator lens unit 20, and a polarization conversion element 40A.

  As shown in FIG. 3, the solid-state light source device 10 is a Lambertian light-emitting diode having a base 12, a solid-state light source 14, a fluorescent layer 16, and a sealing member 18, and includes red light, green light, and blue light. Emits white light. By using such a solid-state light source device 10, the illumination device 100 and the projector 1000 can be reduced in size. The solid-state light source device 10 includes lead wires and the like in addition to the above-described components, but illustration and description thereof are omitted.

  As shown in FIG. 1, the collimator lens unit (collimator optical system) 20 includes a first lens 21 located on the side closer to the solid light source device 10 and a second lens 22 located on the side far from the solid light source device 10. A collimator lens unit that substantially parallelizes the light emitted from the solid-state light source device 10.

  The first lens 21 is a plano-convex lens in which the incident surface is planar and the exit surface is spherical, and has a function of suppressing the spread angle of light from the solid-state light source device 10. The second lens 22 is a convex lens and has a function of collimating the light from the first lens 21.

  Here, the light L from the collimator lens unit 20 includes light L1 traveling in parallel to the illumination optical axis 40ax and light L2 traveling in an oblique direction with respect to the illumination optical axis 40ax ( (See FIG. 4). In the following description, light L2 that travels in an oblique direction with respect to the illumination optical axis 40ax out of the light L emitted from the collimator lens unit 20 is referred to as "oblique light L2."

  The polarization conversion element 40A converts light incident from the collimator lens unit 20 into light mainly composed of S-polarized components. In the present embodiment, P-polarized light is in the first polarization state, and S-polarized light is in the second polarization state. Further, the light composed of the P-polarized component corresponds to the first polarized light, and the light composed of the S-polarized component corresponds to the second polarized light. The illumination device 100 is configured by the polarization conversion element of the first embodiment. This configuration will be described in detail later.

  The liquid crystal light modulation device 50 modulates light incident from the polarization conversion element 40A according to image information to form a color image, and is an illumination target of the illumination device 100. As shown in FIG. 2, the liquid crystal light modulation device 50 has a size slightly smaller than the polarization conversion element 40 </ b> A in a plan view viewed from the front.

  In the present embodiment, the liquid crystal light modulation device 50 is configured as a reflective CF (color filter) type single plate transmission panel. That is, the liquid crystal light modulation device 50 is configured such that a reflective color filter, a liquid crystal element, and the like are sandwiched between a pair of glass substrates, and polarizing plates are bonded to the outer surfaces of these glass substrates. Thus, by using the liquid crystal light modulation device 50 as a single plate type, it is possible to reduce the size of the projector 1000 compared to a three-plate type using a liquid crystal light modulation device for each color light.

  Each polarizing plate transmits either the S-polarized light component or the P-polarized light component, and has, for example, a configuration in which transmission axes are orthogonal to each other (crossed Nicol arrangement). In the present embodiment, the incident-side polarizing plate is composed of an S-transmissive polarizing plate, and the exit-side polarizing plate is composed of a P-transmissive polarizing plate.

  The reflection type color filter includes an R filter, a G filter, and a B filter provided for each pixel. The R filter and the G filter and the B filter transmit red light, green light, and blue light, respectively, and reflect other color lights. In the present embodiment, the color filter has a Bayer arrangement color arrangement structure, but is not limited thereto.

  The liquid crystal element is a liquid crystal element that is hermetically sealed between a color filter and a glass substrate. A polysilicon TFT is used as a switching element, and the polarization direction of incident linearly polarized light according to given image information. Modulate.

  In the liquid crystal light modulation device 50, the linearly polarized light (S-polarized light component in the present embodiment) from the polarization conversion device 40A is transmitted through the incident-side polarizing plate. The linearly polarized light that has passed through the polarizing plate enters the color filter, and only the color light corresponding to the incident filter passes through the filter. The color light transmitted through the filter passes through the liquid crystal element, and its polarization direction is modulated in accordance with image information, and the color light whose polarization direction is modulated (in this embodiment, the color light of the P polarization component) is polarized on the emission side. Inject from the board. Therefore, in the liquid crystal light modulation device 50, a color image corresponding to image information is formed on the emission side by irradiating the linearly polarized light from the polarization conversion element 40A.

  The color image formed by the liquid crystal light modulation device 50 is enlarged and projected by the projection optical system 70 to form an image on the screen.

(Configuration of polarization conversion element)
Next, the polarization conversion element of Embodiment 1 will be described.

  FIG. 4 is a schematic cross-sectional view of the polarization conversion element (the polarization conversion element of the first embodiment) included in the projector shown in FIG. FIG. 5 is a plan view seen from the light exit surface side of the polarization conversion element. In the following description, the horizontal direction in FIG. 4 is referred to as “lateral direction”, and the vertical direction is referred to as “vertical direction”. The left-right direction is a direction in which the S-polarized light incident along the illumination optical axis 40ax is reflected by the polarization separation film 47. The vertical direction is a direction parallel to the illumination optical axis 40ax.

  The polarization conversion element 40A converts the light L incident from the collimator lens unit 20 into light mainly composed of S-polarized components. As shown in FIG. 4, the polarization conversion element 40A includes an optical block 41 including a first optical block 41A and a second optical block 41B, a first total reflection film 42, a phase difference plate 43, an S transmission polarizing plate ( Optical film) 44. The configuration of the first optical block 41A is the same as that of the second optical block 41B, and each of the first optical block 41A and the second optical block 41B includes a polarizing beam splitter 45 and an internal total reflection prism 46. The first optical block 41A and the second optical block 41B are arranged symmetrically with respect to the illumination optical axis 40ax. Therefore, in the following description, the first optical block 41A will be mainly described.

  The first optical block 41A has a polarization beam splitter 45 and an internal total reflection prism 46.

  The polarization beam splitter 45 includes a pair of right-angle prisms 45a and 45a joined with the inclined surfaces facing each other, and a polarization separation film 47 is provided between the joined inclined surfaces. The polarization separation film 47 is a film that reflects the S-polarized component in a direction orthogonal to the illumination optical axis 40ax and transmits the P-polarized component.

  On the other hand, the internal total reflection prism 46 is composed of a pair of right-angle prisms 46a and 46a joined with their slopes facing each other, and a second total reflection film (reflection film) 48 is provided between the joined slopes. Yes. The second total reflection film 48 is a film that reflects the S-polarized component and the P-polarized component. In this embodiment, the S-polarized component reflected by the polarization separation film 47 is reflected in a direction parallel to the illumination optical axis 40ax. .

  The first optical block 41A is configured such that the polarization beam splitter 45 is joined to the internal total reflection prism 46 so that the surface of the polarization separation film 47 is substantially parallel to the surface of the second total reflection film 48. The optical block 41 includes the first optical block 41A in the first optical block 41A so that the surface of the polarization separation film 47 of the first optical block 41A forms an angle of approximately 90 ° with the surface of the polarization separation film 47 of the second optical block 41B. It is comprised by joining to 2 optical block 41B. In this optical block 41, each polarization beam splitter 45 and each internal total reflection prism 46 are arranged in the horizontal direction in the order of the internal total reflection prism 46, the polarization beam splitter 45, the polarization beam splitter 45, and the internal total reflection prism 46. ing.

  Of the plurality of surfaces of the optical block 41 as described above, the surface on the side where the inclined surfaces of the polarization beam splitters 45 are in contact constitutes the light incident surface S41 on which the light L from the collimator lens unit 20 is incident. Moreover, the area | region in which the 1st total reflection film 42 mentioned later among the light-incidence surfaces S41 of the optical block 41 is not formed comprises light guide opening A3 into which the light L is introduce | transduced in the polarization conversion element 40A. On the other hand, the surface facing the light incident surface S41 among the plurality of surfaces of the optical block 41 constitutes a light emitting surface S42 for emitting light composed of S-polarized components.

  In the following description, a region corresponding to the light exit surface of the polarization beam splitter 45 in the light exit surface S42 is referred to as “first region A1”. In other words, the first region A1 is a region that overlaps the polarization separation film 47 in plan view in the light exit surface S42 when the light exit surface S42 is viewed from a direction parallel to the illumination optical axis 40ax. In addition, a region corresponding to the light exit surface of the internal total reflection prism 46 in the light exit surface S42 is referred to as a “second region A2”. In other words, the second region A2 is a region that overlaps the second total reflection film 48 in plan view in the light exit surface S42 when the light exit surface S42 is viewed from a direction parallel to the illumination optical axis 40ax.

  The polarization separation film 47 is opposed to the first region A1 and the light guide opening A3 so as to form an angle of about 45 °.

  Next, each part provided in the light incident surface S41 and the light exit surface S42 of the optical block 41 will be described.

  When the light incident surface S41 is viewed from a direction parallel to the illumination optical axis 40ax, a first total reflection film 42 is provided in a region of the light incident surface S41 that overlaps the internal total reflection prism 46 in plan view. . The first total reflection film 42 is a film that reflects light (both S-polarized component and P-polarized component) incident from the collimator lens unit 20 in a direction substantially parallel to the illumination optical axis 40ax.

  When the light exit surface S42 is viewed from a direction parallel to the illumination optical axis 40ax, a phase difference plate 43 is provided in a region of the light exit surface S42 that overlaps with the polarization beam splitter 45 in plan view. The retardation plate 43 is a λ / 2 plate and has a function of converting the P-polarized light component transmitted through the polarization separation film 47 into an S-polarized light component by rotating the polarization direction by 90 °. The above is the basic configuration of the first optical block 41A, but the basic configuration of the second optical block 41B is the same as described above. The above is the basic configuration of the polarization conversion element 40A.

  In the polarization conversion element 40A of the present embodiment, in particular, as shown in FIG. 5, the S transmission polarizing plate 44 is provided in a region along the boundary between the second region A2 and the first region A1. The S transmissive polarizing plate 44 is a band-shaped polarizing plate that transmits the S polarized component and shields the P polarized component. The S transmission polarizing plate 44 is provided so as to be adjacent to the phase difference plate 43 so that the extending direction thereof substantially coincides with a direction (vertical direction) orthogonal to the reflection direction of the S polarization component in the polarization separation film 47. Yes.

  In the polarization conversion element 40A configured as described above, the light L from the collimator lens unit 20 enters from the light incident surface. Here, the light L from the collimator lens unit includes the light L1 traveling in the direction parallel to the illumination optical axis 40x and the oblique light L2 traveling in the oblique direction with respect to the illumination optical axis 40ax as described above. include. Also in the following description, the operation of the first optical block 41A will be mainly described. Since the operation of the second optical block 41B is the same as that of the first optical block 41A, description thereof is omitted.

  Of the light from the collimator lens unit 20, the light incident on the first total reflection film 42 is reflected by the first total reflection film 42 in a direction parallel to the illumination optical axis 40 ax, and the second lens of the collimator lens unit 20. 22 is incident. The light that has entered the second lens 22 from the first total reflection film 42 is collected by the second lens 22 and the first lens 21 and enters the solid-state light source device 10. The light incident on the solid light source device 10 is reflected by the solid light source device 10 and reused as light introduced into the polarization conversion element 40A. Therefore, in this illuminating device 100, it is possible to use efficiently the light emitted from the solid light source device 10.

  Further, the light L incident on the light guide opening A <b> 3 out of the light from the collimator lens unit 20 travels into the polarization beam splitter 45 and enters the polarization separation film 47. Of the light incident on the polarization separation film 47, the S-polarized component is reflected by the polarization separation film 47 in the direction orthogonal to the illumination optical axis 40 ax and enters the second total reflection film 48. The S-polarized component incident on the second total reflection film 48 is reflected by the second total reflection film 48 in a direction parallel to the illumination optical axis 40ax. As a result, the S-polarized component incident from the light guide opening A3 moves in parallel from the polarization beam splitter 45 toward the internal total reflection prism 46, and is emitted from the second region A2 on the light exit surface as S-polarized light. Of the light incident on the polarization separation film 47, the P-polarized component is transmitted through the polarization separation film 47. The P-polarized component transmitted through the polarization separation film 47 enters the phase difference plate 43, is converted into an S-polarized component, and is emitted from the first region A1 on the light exit surface. Therefore, the light incident on the polarization separation film 47 from the light guide opening A3 of the polarization conversion element 40A is emitted from the first area A1 and the second area A2 as the S-polarized component, and is incident on the irradiation surface of the liquid crystal light modulation device 50. Irradiated.

  On the other hand, a part of the oblique light L2 incident on the light guide opening A3 on the light incident surface from an oblique direction with respect to the illumination optical axis ax is shifted from the original optical path, and therefore does not enter the polarization separation film 47 and is guided. The light enters directly from the mouth A3 near the boundary with the phase difference plate 43 in the second region A2. Here, the oblique light incident near the boundary includes both the S-polarized component and the P-polarized component because it does not pass through the polarization separation film 47, the phase difference plate 43, and the second total reflection film 48. It is incident on an area different from the area to be emitted. For this reason, if the light is emitted as it is, the amount of light emitted near this boundary becomes larger than that in other regions, which causes illuminance unevenness.

  On the other hand, in the polarization conversion element 40A of the present embodiment, the S transmission polarizing plate 44 is provided in a region along the boundary between the second region A2 and the first region A1. The S transmission polarizing plate 44 is provided so as to be adjacent to the phase difference plate 43 provided in the first region A1. Therefore, in the oblique light L2 incident near the boundary with the phase difference plate 43 in the second region A2, the S polarization component is transmitted through the S transmission polarizer 44, but the P polarization component is emitted from the S transmission polarizer 44. 44 is shielded. For this reason, it is suppressed that the P-polarized light component is emitted from the vicinity of the boundary, and the difference in the amount of emitted light between the vicinity of the boundary and other regions is reduced or eliminated. As a result, the polarization conversion element 40A can increase the in-plane uniformity at the light exit surface S42 of the exit light intensity.

  Here, the transmittance of the S transmission polarizing plate 44 is not necessarily 100% with respect to the S polarization, and a part of the S polarization is absorbed by the S transmission polarization plate 44. S-polarized light passing through the original route, that is, S-polarized light reflected by the polarization separation film 47 and reflected by the second total reflection film 48 also enters the S-transmissive polarizing plate 44. However, in the polarization conversion element 40A of the present embodiment, since the S transmission polarizing plate 44 is provided not in the entire surface of the second region A2 but in the region where the oblique light L2 is incident in the second region A2, the original route is used. Thus, the S polarized light emitted from the region where the S transmissive polarizing plate 44 is not provided is not absorbed by the S transmissive polarizing plate 44.

  On the other hand, the oblique light L2 and S-polarized light that has passed through the original route are incident on the S-transmissive polarizing plate 44. The S transmission polarizing plate 44 transmits a part (S-polarized light) of the oblique light L2, but absorbs a part of the S-polarized light via the original route. Therefore, the difference between the amount of light emitted from the S transmissive polarizing plate 44 in the second region A2 and the amount of light emitted from the region of the second region A2 where the S transmissive polarizing plate 44 is not provided is represented by the entire surface of the second region A2. It can be made smaller than when the S transmissive polarizing plate 44 is provided. Thereby, the polarization conversion element 40A can further increase the in-plane uniformity at the light exit surface S42 of the exit light intensity.

  FIG. 6 is an illumination image of light emitted from the polarization conversion element 40A of Embodiment 1, and FIG. 7 is an illumination image of light emitted from a polarization conversion element not provided with the S transmission polarizing plate. From each figure, in the polarization conversion element 40A of Embodiment 1, it can be confirmed that a good illumination image with little unevenness can be obtained by providing the S transmission polarizing plate 44.

  Here, the S transmissive polarizing plate 44 may be a reflective S transmissive polarizing plate that reflects the P-polarized component, or an absorbing S transmissive polarizing plate that absorbs the P-polarized component. Of these, the use of a reflective S-transmission polarizing plate has the effect that the reflected P-polarized component returns to the solid-state light source device 10 and is reflected by the solid-state light source device 10 and can be reused as light to be introduced into the polarization conversion element 40A. can get.

Moreover, it is preferable that the width | variety of the S transmissive polarizing plate 44 is the range shown by a following formula.
L · tan θ−0.1 ≦ d ≦ L · tan θ + 0.1
d: Width (mm) of the S transmission polarizing plate 44
L: Thickness of the polarization conversion element (length in the direction of the illumination optical axis 40ax) (mm)
θ: an angle formed by the traveling direction of the oblique light L2 incident on the second region A2 and the illumination optical axis 40ax.

  To be precise, L is the distance between the light incident surface S41 and the light exit surface S42. The illumination optical axis 40ax corresponds to the principal ray axis of the light emitted from the light exit surface S42. Specifically, d is about 0.2 to 0.4 mm.

  In the above equation, L · tan θ corresponds to the width of the incident region in the second region A2 of the oblique light incident on the second region A2 without passing through the polarization separation film 47. θ is a diffusion angle of light emitted from the collimator lens unit 20. The diffusion angle is, for example, an angle when the light amount decreases to 50% of the peak light amount when the horizontal axis is the angle formed by the illumination optical axis 40a and the vertical axis is the amount of light emitted at that angle. Is calculated as

  Therefore, when the width of the S transmissive polarizing plate 44 is narrower than the above range, a part of the oblique light L2 incident on the second region A2 does not enter the S transmissive polarizing plate 44 and remains as it is from the second region A2. It may be emitted and cause uneven illumination. Further, when the width of the S transmission polarizing plate 44 is wider than the above range, the S polarization component passing through the original route is incident on a region outside the region where the oblique light L2 is incident in the S transmission polarizing plate 44. Will do. Then, since the transmittance of the S-polarized light component of the S-transparent polarizing plate 44 is not 100%, when the S-polarized light component enters the S-transmissive polarizing plate 44 outside the region where the oblique light is incident, Becomes smaller than the amount of light emitted from other regions. As a result, there is a possibility that the portion corresponding to this region on the light irradiation surface becomes dark.

  The transmittance of the S polarization component of the S transmission polarizing plate 44 is preferably 85 to 95%. As described above, since the transmittance of the S polarization component of the S transmission polarizer 44 is lower than 100%, the amount of the S polarization component emitted from the S transmission polarizer 44 is changed to the S polarization of the oblique light L2 incident thereon. The amount of light corresponding to the component, or the amount of light corresponding to at least a part thereof can be reduced. As a result, the difference in the amount of emitted light between the region where the oblique light L2 is incident and the other region can be further reduced or eliminated. However, when the transmittance of the S-polarized component is lower than 85%, the amount of the S-polarized component emitted from the S-transmissive polarizing plate 44 becomes too small, and the portion corresponding to this region on the light irradiation surface becomes dark. there is a possibility.

  As described above, in this polarization conversion element 40A, the S-transmission polarizing plate 44 is provided in the vicinity of the boundary between the second region A2 and the first region A1 on the light exit surface S42. The in-plane uniformity at the strong light exit surface S42 can be increased.

  Therefore, the illuminating device 100 of Embodiment 1 including such a polarization conversion element 40A can uniformly irradiate the light irradiation surface of the liquid crystal light modulation device 50 to be illuminated with the S-polarized component.

  In addition, the projector 1000 according to the first embodiment including the illumination device 100 can display a high-quality image without uneven brightness.

<Embodiment 2>
Next, a second embodiment of the polarization conversion element, illumination device, and projector of the present invention will be described.

  In the second embodiment, the differences from the first embodiment will be mainly described, and the description of the same matters will be omitted. In the following description, the first optical block 41A will be mainly described.

  The illumination device of Embodiment 2 has the same configuration as that of Embodiment 1 except that the configuration of the polarization conversion element is different. In this embodiment, unlike the first embodiment, S-polarized light is in the first polarization state, and P-polarized light is in the second polarization state. Further, the light composed of the S-polarized component corresponds to the first polarized light, and the light composed of the P-polarized component corresponds to the second polarized light. The projector according to the second embodiment is different from the configuration of the polarization conversion element included in the illumination device, except that the incident side polarizing plate of the liquid crystal light modulation device is a P transmission polarizing plate and the emission side polarizing plate is an S transmission polarizing plate. The configuration is the same as that of the first embodiment.

  Hereinafter, the configuration of the polarization conversion element (polarization conversion element of Embodiment 2) will be described.

  FIG. 8 is a schematic cross-sectional view of the polarization conversion element of the second embodiment. FIG. 9 is a plan view seen from the light exit surface side of the polarization conversion element.

  The polarization conversion element 40B converts light incident from the collimator lens unit 20 into light mainly composed of a P-polarized component. The polarization conversion element 40B includes an optical block 41, a first total reflection film 42 provided on the surface of the optical block 41, a retardation plate (λ / 2 plate) 43, and an ND film (Neutral Density Filter as an optical film). 49). In place of the ND film 49, a P transmission polarizing plate may be disposed.

  The configurations of the optical block 41 and the first total reflection film 42 provided on the incident surface of the optical block 41 are the same as those in the first embodiment.

  A phase difference plate 43 is provided in a region of the light exit surface S42 that overlaps the internal total reflection prism 46 in plan view when the light exit surface S42 is viewed from a direction parallel to the illumination optical axis 40ax. The phase difference plate 43 has a function of converting the S polarization component reflected by the polarization separation film 47 and the second total reflection film 48 into a P polarization component by rotating the polarization direction by 90 °.

  As shown in FIG. 9, the ND filter 49 is provided in a region along the boundary between the second region A2 and the first region A1. The ND filter 49 is a belt-like optical film that reduces the amount of light passing through the ND filter 49, and the extending direction of the ND filter 49 is perpendicular to the reflection direction of the S-polarized light component on the polarization separation film 47 (vertical direction). ) So as to be adjacent to the first region A1.

  In the polarization conversion element 40 configured as described above, the light L from the collimator lens unit 20 is incident from the incident surface. Here, the light L from the collimator lens unit 20 includes the light L1 traveling in a direction parallel to the illumination optical axis 40ax and the oblique light L2 traveling in an oblique direction with respect to the illumination optical axis 40ax as described above. Are mixed. Also in the following description, the operation of the first optical block 41A will be mainly described. Since the operation of the second optical block 41B is the same as that of the first optical block 41A, description thereof is omitted.

  Of the light from the collimator lens unit 20, the light L incident on the first total reflection film 42 returns to the solid light source device through the same path as in the first embodiment, is reflected from the solid light source device 10, and is converted into the polarization conversion element 40 </ b> B. Reused as light to be introduced into.

  Further, the light L incident on the light guide opening A <b> 3 out of the light from the collimator lens unit 20 travels into the polarization beam splitter 45 and enters the polarization separation film 47. Of the light incident on the polarization separation film 47, the S-polarized component is reflected by the polarization separation film 47 and the second total reflection film 48, so that the optical path is parallel to the internal total reflection prism 46 side from the polarization beam splitter 45. Moving. Then, the S-polarized component moved to the internal total reflection prism 46 side is incident on the phase difference plate 43, converted into a P-polarized component, and emitted from the second region A2 on the light exit surface. Of the light incident on the polarization separation film 47, the P-polarized component is transmitted through the polarization separation film 47. The P-polarized component transmitted through the polarization separation film 47 is emitted as P-polarized light from the first region A1 on the light exit surface. Accordingly, the light incident on the polarization separation film 47 of the polarization conversion element 40B is emitted from the first region A1 and the second region A2 as a P-polarized component, and is irradiated on the irradiation surface of the liquid crystal light modulation device 50.

  On the other hand, a portion of the oblique light L2 that is incident on the light guide opening A3 on the light incident surface from an oblique direction with respect to the illumination optical axis 40ax is not incident on the polarization separation film 47 because it is deviated from the original optical path. The light directly enters the vicinity of the boundary between the second region A2 and the first region A1 from the mouth A3. Here, the oblique light incident near the boundary includes the P-polarized component and the S-polarized component as described above, and is incident on a region different from the region to be originally emitted. If this is done, the amount of light emitted in the vicinity of this boundary will be larger than in other areas, causing unevenness in illuminance.

  On the other hand, in the polarization conversion element 40B of the present embodiment, the ND filter 49 is provided in a region along the boundary between the second region A2 and the first region A1. The ND filter 49 is provided adjacent to the first region A1. Therefore, the oblique light L2 incident near the boundary between the second region A2 and the first region A1 passes through the ND filter 49, and at that time, the amount of light is reduced. For this reason, the difference in the amount of emitted light between the vicinity of the boundary and other regions is reduced or eliminated. As a result, the polarization conversion element 40B can increase the in-plane uniformity at the light exit surface S42 of the exit light intensity.

  The appropriate range of the width of the ND filter 49 is the same as that of the S-transmission polarizing film in the first embodiment.

  In the second embodiment, it is possible to obtain the same effect as in the first embodiment.

<Modification>
In the second embodiment, the ND film 49 is used. However, a P transmission polarizing plate may be used instead of the ND film 49. Since the only difference between the polarization conversion element according to the present modification and the polarization conversion element 40B according to the second embodiment is to use a P-transmission polarizing plate instead of the ND film 49, description of common matters is omitted.

  The P transmission polarizing plate is provided on the side opposite to the internal total reflection prism 46 of the retardation plate. A part of the oblique light L2 (P-polarized light) out of the light L incident from the light guide opening A3 is transmitted through the P-transmissive polarizing plate, but is reflected by the P-polarized light passing through the original route, that is, the polarization separation film 47, Since a part of the P-polarized light that is reflected by the second total reflection film 48 and whose polarization direction is converted by the phase difference plate 43 is absorbed, the amount of light emitted from the P-transmissive polarizing plate does not increase greatly. Even in the polarization conversion element according to this modification, the in-plane uniformity of the light exit surface at the light exit surface S42 can be increased.

  Here, the transmittance of the P transmissive polarizing plate is not necessarily 100% with respect to the P polarized light, and a part of the P polarized light is absorbed by the P transmissive polarizing plate. When the P transmission polarizing plate is used, the S polarized light after passing through the retardation plate 43 in the oblique light L2 is shielded by the P transmission polarizing plate. P-polarized light that has passed through the original route also enters the P-transmissive polarizing plate. However, in the polarization conversion element of the present modification, the P transmission polarizing plate is provided not in the entire area of the second area A2 but in the area where the oblique light L2 is incident in the second area A2, and therefore, via the original route. The P-polarized light emitted from the region where the P-transmissive polarizing plate is not provided is not absorbed by the P-transmissive polarizing plate.

  On the other hand, the oblique light L2 and the P-polarized light passing through the original route are incident on the P-transmissive polarizing plate. The P-transmissive polarizing plate transmits a part of the oblique light L2 (P-polarized light), but absorbs a part of the P-polarized light passing through the original route. Therefore, the difference between the amount of light emitted from the P transmissive polarizing plate in the second region A2 and the amount of light emitted from the region of the second region A2 where the P transmissive polarizing plate is not provided is expressed on the entire surface of the second region A2. It can be made smaller than when a transmissive polarizing plate is provided. As a result, the polarization conversion element according to the present modification can further increase the in-plane uniformity of the emission light intensity at the light exit surface S42.

  As mentioned above, although this invention was demonstrated based on Embodiment 1, Embodiment 2, and a modification, this invention is not limited to the said structure. The present invention can be carried out in various modes without departing from the gist thereof, and for example, the following modifications are possible.

(1) In each said embodiment, an optical film is not restricted to this, For example, in said Embodiment 1, you may make it use a ND film instead of a S transmissive polarizing plate.

(2) In the polarization conversion elements of the above embodiments, the S-polarized component and the P-polarized component may be reversed. That is, in the first embodiment, the P-polarized light is in the first polarization state, but the S-polarized light may be in the first polarization state. In this case, if a polarizing plate is used as the optical film, a P transmission polarizing plate is used. In the second embodiment, the S-polarized light is in the first polarization state, but the P-polarized light may be in the first polarization state. In this case, if a polarizing plate is used as the optical film, an S transmissive polarizing plate is used.

(3) In the first embodiment, the S transmissive polarizing plate 44 is provided so as to be adjacent to the retardation plate 43, but the S transmissive polarizing plate 44 may partially overlap the retardation plate 43. Good.

(4) The present invention is applied to a rear projection projector that projects from a side opposite to the side that observes the projected image, even when applied to a front projection projector that projects from the side that observes the projected image. Is also possible.

(5) In each of the above embodiments, the example in which the illumination device of the present invention is applied to a projector has been described, but the present invention is not limited to this. For example, the lighting device of the present invention can also be applied to other optical devices (for example, optical disk devices, automobile headlamps, various lighting fixtures, etc.).

DESCRIPTION OF SYMBOLS 10 ... Solid light source device, 20 ... Collimator optical unit (collimator optical system), 40A, 40B ... Polarization conversion element, 43 ... Phase difference plate, 44 ... S transmission polarizing plate (optical film), 47 ... Polarization separation film, 48: second total reflection film (reflection film), 49: ND filter (optical film), 50: liquid crystal light modulation device, 70: projection optical system, 100: illumination device, 1000: projector, A1: first region, A2 ... second region, S41 ... light incident surface, S42 ... light exit surface,

Claims (9)

A light incident surface;
A light exit surface having a first region and a second region adjacent to each other;
The first polarized light of the first polarization state of the incident light incident on the light incident surface is transmitted toward the first region, and is disposed so as to face the first region obliquely. A polarization separation film that reflects the second polarized light in the second polarization state,
A reflective film that reflects the second polarized light reflected by the polarization separation film toward the second region;
A retardation plate provided in the first region and converting the polarization state of the first polarized light from the first polarization state to the second polarization state;
An optical film that is provided in a region along the boundary between the second region and the first region, and that reduces the amount of light emitted from the second region. A light incident surface;
A light exit surface having a first region and a second region adjacent to each other;
The second polarized light in the second polarization state is transmitted toward the first region and is incident on the light incident surface. A polarization separation film that reflects the first polarized light in the first polarization state,
A reflective film that reflects the first polarized light reflected by the polarization separation film toward the second region;
A retardation plate provided in the second region and converting the polarization state of the first polarized light from the first polarization state to the second polarization state;
An optical film that is provided in a region along the boundary between the second region and the first region, and that reduces the amount of light emitted from the second region.   The polarization conversion element according to claim 1, wherein the optical film is a polarizing plate that transmits the second polarized light and shields the first polarized light.   4. The polarization conversion element according to claim 1, wherein the optical film has a strip shape extending in a direction orthogonal to a light reflection direction in the polarization separation film. 5. 5. The polarization conversion element according to claim 1, wherein the width of the optical film is in a range represented by the following formula.
L · tan θ−0.1 ≦ d ≦ L · tan θ + 0.1
d: Width of optical film (mm)
L: Thickness of polarization conversion element (mm)
θ: an angle formed between the traveling direction of light incident on the second region from the light incident surface without passing through the polarization separation film in the incident light and the principal ray axis of light emitted from the light exit surface A collimator lens unit that substantially collimates the light emitted from the solid-state light source device;
A polarization conversion element on which light emitted from the collimator lens unit is incident;
A lighting device comprising:
The said polarization conversion element is a polarization conversion element in any one of Claims 1-5, The illuminating device characterized by the above-mentioned.   The illumination device according to claim 6, wherein the solid-state light source device is a white light source having an excitation light source made of a light emitting diode or a semiconductor laser and a phosphor. A lighting device;
A light modulation device that modulates illumination light from the illumination device according to image information;
A projection optical system that projects modulated light from the light modulation device as a projection image;
A projector comprising:
The projector according to claim 6 or 7, wherein the lighting device is the lighting device according to claim 6 or 7.   The projector according to claim 8, wherein the light modulation device is a single-plate liquid crystal light modulation device.