JP2013076904A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device that can eliminate a ghost image.SOLUTION: A light source 10 emits a blue laser beam. A light modulation element 2 modulates the blue laser beam emitted from the light source 10 according to a video signal. A phosphor is excited to emit light by the blue laser beam. An imaging lens 15 focuses the blue laser beam modulated by the light modulation element 2 onto the phosphor. A dichroic mirror is arranged between the phosphor and the imaging lens 15 with being inclined to an optical path of the blue laser beam, and transmits light in blue colour band. A projector lens projects an image formed on a fluorescent plate by the imaging lens 15 to the outside.

Description

  The present invention relates to a display device using a reflective light modulation element.

  2. Description of the Related Art Conventionally, there is known a projection type display device that projects modulated light spatially modulated by a reflection type light modulation element (liquid crystal display element) that controls liquid crystal in pixel units onto a screen via a projection lens or the like. . In such a display device, illumination light (white light) emitted from a light source is color-separated into illumination light of red (R) light, green (G) light, and blue (B) light by a dichroic mirror, The light enters the reflective light modulation element corresponding to each color via the illumination optical system.

  These illumination lights are converted into linearly polarized light in a predetermined direction before being incident on each reflection type light modulation element, and wires for each color light installed so as to transmit only the polarization component in the predetermined direction. Transmits through the grid polarizer. The wire grid polarizer reflects the modulated light that is polarization-modulated by a reflective light modulation element or the like, and branches the modulated light from the optical path that returns to the illumination optical system. The modulated light reflected by the wire grid polarizer further passes through the polarizer, is color-combined by the dichroic prism, and enters the projection lens. The projection lens projects the incident modulated light on a screen to form an image, and displays an image.

  In such a projection display device, when a laser light source is used as the light source, there is a problem that the image quality of the display image is deteriorated due to speckle noise generated on the screen. Further, depending on the state of the display device, the reflected and scattered light in the optical system may return to the optical path again, and a ghost image may be generated on the screen. As a method for removing the ghost image, a λ / 4 plate is arranged in the immediate vicinity of the projection lens, the polarization direction of the light returning from the optical path is rotated by 90 °, and the light is reflected by the wire grid polarizer. It has been proposed to make the structure not return to the type light modulation element (see Patent Document 1).

Japanese Patent No. 3470491

For example, in a display device that modulates light emitted from a laser light source with a light modulation element and forms an image on the screen once formed on the phosphor, the return light from the phosphor and the projection lens is light modulated. A ghost that reaches the element, passes through the projection lens again, and is generated on the screen has been a problem.
In view of the above problems, an object of the present invention is to provide a display device that removes a ghost image.

  In order to achieve the above object, according to an aspect of the present invention, a light source (10) that emits blue laser light, and a light modulation element that modulates the laser light emitted from the light source (10) according to a video signal ( 2), a phosphor (31) excited and emitted by blue laser light, and an imaging lens (15) for imaging the laser light modulated by the light modulation element (2) on the phosphor (31) A dichroic mirror (16) that is installed between the phosphor (31) and the imaging lens (15) so as to be inclined with respect to the optical path of the laser beam and transmits blue band light; and The gist of the invention is a display device including a projection lens that projects an image formed on the phosphor (31) by the image lens (15) to the outside.

  In the display device according to the aspect of the present invention, the phosphor (31) may be two types of phosphors that emit red and green light.

  In the display device according to the aspect of the present invention, the light modulation element (2) can be sequentially controlled so as to modulate the laser light according to video signals of different channels every time.

  The display device according to the aspect of the present invention further includes a flat wheel (6) provided perpendicular to the optical path of the blue laser light, and the phosphor (31) includes the wheel (6). The wheel (6) can be rotated at a predetermined rotational speed in synchronization with the blue laser light.

  ADVANTAGE OF THE INVENTION According to this invention, the display apparatus which removes a ghost image can be provided.

1 is a schematic diagram illustrating a basic configuration of a display device according to an embodiment of the present invention. It is a schematic diagram explaining the optical unit with which the display apparatus which concerns on embodiment of this invention is provided. It is typical sectional drawing explaining the reflection type light modulation element with which the display apparatus which concerns on embodiment of this invention is provided. It is a table | surface explaining an example of the fluorescent substance used for the display apparatus which concerns on embodiment of this invention. It is a typical figure explaining the fluorescent substance used for the display apparatus which concerns on embodiment of this invention. It is a typical figure explaining the ghost image which may arise in the display apparatus which concerns on embodiment of this invention. It is a typical figure explaining a mode that a ghost image is removed in the display apparatus which concerns on embodiment of this invention. It is a figure explaining the characteristic of the dichroic mirror with which the display apparatus which concerns on embodiment of this invention is provided. It is a typical figure explaining the display apparatus which concerns on the modification of embodiment of this invention. It is a typical figure explaining the wheel with which the display apparatus which concerns on the modification of embodiment of this invention is provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the embodiment described below exemplifies an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention is an apparatus exemplified in the following embodiment. It is not specific to the method. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

  As shown in FIG. 1, the display device according to the embodiment of the present invention includes optical units 1R, 1G, and 1B that emit light, a fluorescent plate 3R that emits red light, a fluorescent plate 3G that emits green light, A diffusing plate 4, an X prism 5, and a projection lens 8 are provided.

  The optical unit 1R irradiates the fluorescent plate 3R with blue laser light as light for a red channel (Rch). The fluorescent plate 3R is excited by the light of the optical unit 1R and emits red light. The optical unit 1G irradiates the fluorescent plate 3G with blue laser light as light for a green channel (Gch). The fluorescent plate 3G is excited by the light of the optical unit 1G and emits green light. The optical unit 1B irradiates the diffusion plate 4 with blue laser light as blue channel (Bch) light. The diffuser plate 4 removes speckle noise from the light emitted from the optical unit 1B.

  The X prism 5 synthesizes RGB three-color light via the fluorescent plates 3R and 3G and the diffusion plate 4 and emits the light toward the projection lens 8. The projection lens 8 projects the light emitted from the X prism 5 onto the screen 9.

  The structures of the optical units 1R, 1G, and 1B (hereinafter collectively referred to as “optical unit 1”) may be the same. As shown in FIG. 2, the optical unit 1 includes a light source unit 10, a condenser lens 11, a light tunnel 12, imaging lenses 13 and 15, a polarization beam splitter (PBS) 14, and a reflective light modulation element 2. And a drive unit 25.

  The light source unit 10 includes a blue laser light source arranged in a two-dimensional array, and emits laser light to the condenser lens 11. The laser light emitted from the light source unit 10 is condensed by the condenser lens 11 and enters the light tunnel 12. The light tunnel 12 has, for example, a hollow rectangular shape, and an inner wall surface is configured by a mirror. The inner wall surface of the light tunnel 12 is formed, for example, by forming a metal film such as silver (Ag) or aluminum (Al) on the surface of flat glass. The light tunnel 12 reflects the laser light incident from the incident opening on one end side a plurality of times inside, uniformizes the luminance distribution of the laser light, and emits it from the exit opening on the other end side. In each part of the optical unit 1, each laser light source is set in an optimal state so that the laser light at the exit opening of the light tunnel 12 is polarized in a regular polarization direction of the electric and magnetic fields.

  The imaging lens 13 forms an image of the laser beam, which is polarized light emitted from the light tunnel 12, on the reflective light modulation element 2 via the PBS 14. The PBS 14 has a reflecting surface that transmits, for example, P-polarized light and reflects S-polarized light, so that the optical path of P-polarized light and the optical path of S-polarized light can be branched. When the laser light emitted from the light tunnel 12 and passing through the imaging lens 13 is S-polarized light, the PBS 14 may have a reflecting surface that transmits S-polarized light and reflects P-polarized light.

  For example, as shown in FIG. 3, the reflective light modulation element 2 has a substrate 21 made of silicon (Si) or the like, a plurality of reflective electrodes 22 provided on the upper surface of the substrate 21, and a predetermined distance from the substrate 21. And a transparent substrate 24 provided with a transparent electrode (not shown) provided on the surface facing the reflective electrode 22, and a light modulation layer 23 positioned between the substrate 21 and the transparent substrate 24.

  Each of the plurality of reflective electrodes 22 corresponds to a pixel, and a voltage applied between the reflective electrodes 22 and the transparent electrode is controlled by the driving unit 25 according to the video signal. The light modulation layer 23 is made of, for example, a light modulation material such as liquid crystal having birefringence. The drive unit 25 controls the drive of the reflective light modulation element 2.

  Laser light emitted from the light tunnel 12 and converted to, for example, P-polarized light is transmitted through the reflecting surface that transmits the P-polarized light of the PBS 14 by the imaging lens 13 and forms an image on the reflective light modulation element 2. The laser light incident on the reflection type light modulation element 2 as P-polarized light is optically modulated in the reflection type light modulation element 2 in accordance with the video signal. That is, most of the light corresponding to the dark pixel is reflected to the PBS 14 side while being P-polarized light, and most of the light corresponding to the bright pixel becomes S-polarized light and is reflected toward the imaging lens 15 on the reflection surface of the PBS 14, To be separated.

  The S-polarized light reflected by the PBS 14 is imaged on the fluorescent plate 3 by the imaging lens 15. The imaged fluorescent plate 3 has a light and shade corresponding to the video signal formed on the surface, and the phosphor of the fluorescent plate 3 is excited and emits light according to the light and shade.

  Since the coherence of the laser light imaged on the fluorescent plate 3 is preserved, speckle noise is generated, but it is converted into incoherent light by the phosphor applied to the fluorescent plate 3, and the speckle noise is completely removed. be able to. Therefore, the observer can appreciate the image without noise.

For example, as shown in FIG. 4, phosphors such as Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce ³⁺ , Ba ₉ Sc ₂ Si ₆ O ₂₄ : Eu ²⁺ , Sr ₃ Si ₁₃ Al ₃ O ₂ N ₂₁ are By using blue laser light as an excitation line, light is emitted in green. A phosphor such as Ca ₃ Si ₂ O ₇ : Eu ²⁺ emits red light by using blue laser light as an excitation line. Therefore, these phosphors can be used for the fluorescent plate 3. The fluorescent plate 3 can be easily prepared by mixing a phosphor with a silicone resin, applying it on a glass substrate and sintering it. The pixel structure of the fluorescent plate 3 is not necessary.

  By thinly applying a coating material containing a fine particle phosphor to the fluorescent plate 3, the image formed on the fluorescent plate 3 can be prevented from being blurred. For example, as shown in FIG. 5, the thickness of the phosphor can be reduced to about 1.5 times that of phosphor particles having a diameter of about 10 μm.

  In addition, since the phosphor has a property of emitting light having a long wavelength (Rch or Gch) when irradiated with light having a short wavelength (in this case, Bch), a blue laser is used as an excitation line of the phosphors of Rch and Gch. Using light.

  In addition, the speckle of the blue laser light has low visibility, and it is not necessary to actively increase the wavelength by wavelength conversion by the fluorescent plate 3 and to reduce coherence. However, since speckles are generated, in Bch, the light beam angle is widened by the diffusion plate 4 to further reduce speckles.

  In the above structure, as shown in FIG. 6, the reflected light from the fluorescent plate 3 and the projection lens 8 returns to the reflective light modulation element 2 again, and the path of the PBS 14, the imaging lens 15, the fluorescent plate 3, and the projection lens 8 again. May reach the screen and become a ghost image such as a double image. On the other hand, as shown in FIG. 7, the display device according to the embodiment of the present invention has a dichroic mirror 16 disposed between the imaging lens 15 and the fluorescent plate 3 so as to be inclined with respect to the optical axis. Can be provided.

  For example, as shown in FIG. 8, the dichroic mirror 16 has a transmittance T of about 100% for light having a wavelength of about 400 nm to 450 nm, which is a blue laser light band, and for light having a wavelength of about 450 nm to 700 nm. Thus, the reflectance R is about 100%. When the light that has passed through the imaging lens 15 passes through the dichroic mirror 16, it passes through the dichroic mirror 16 because it is blue laser light. After that, the reflected light generated by the fluorescent plate 3 and the projection lens 8 is Rch red light or Gch green light excited by the fluorescent material by the blue laser light, and is reflected by the dichroic mirror 16 so that Rch, The Gch ghost image can be removed.

  According to the display device according to the embodiment of the present invention, the reflected light from the fluorescent plate 3 and the projection lens 8 can be separated from the optical path by the dichroic mirror 16, so that the ghost image generated on the screen 9 can be removed.

(Modification)
The optical unit 1A included in the display device according to the modification of the embodiment of the present invention illustrated in FIG. 9 has the same configuration as the optical unit 1 illustrated in FIG. 2, but the drive unit 25 includes Rch, Gch, and Bch, respectively. The reflective light modulation element 2 can be sequentially controlled in accordance with the video signal. That is, the blue laser light emitted from the optical unit 1A becomes Rch, Gch, and Bch signal light every time. Blue laser light emitted from the optical unit 1 </ b> A is incident on the wheel 6.

  As shown in FIGS. 9 and 10, the wheel 6 is a flat wheel substrate 60 made of a transparent material such as glass or resin, and the Rch for Rch divided into three segments provided on the surface of the wheel substrate 60. A phosphor 31R, a Gch phosphor 31G, and a Bch diffusion film 41 are provided. The rotation speeds of the optical unit 1A and the wheel 6 are synchronized with the blue laser light emitted from the optical unit 1A, and when the Rch, Gch, and Bch signal lights are emitted, the phosphor 31R and the phosphor, respectively. 31G is set to a predetermined value so as to enter the diffusion film 41. The wheel 6 rotates at a speed of about 120 Hz, for example.

  When modulated blue laser light is focused on the Rch phosphor 31R, an Rch image is obtained. Similarly, when blue laser light is imaged for Gch, it becomes a Gch image, and when it is imaged on the diffusion film 41 for Bch, it becomes a Bch image. The dichroic mirror 16 is disposed between the optical unit 1A and the wheel 6 so as to be inclined with respect to the optical path. As shown in FIG. 8, for example, the dichroic mirror 16 has a characteristic that light having a wavelength of about 400 nm to 450 nm, which is a blue laser light band, is transmitted, and light having a wavelength of about 450 nm to 700 nm is reflected. ing.

  Since the imaging light indicating the image of each channel emitted from the optical unit 1A is blue laser light, it passes through the dichroic mirror 16 as it is. Of the light imaged on the wheel 6, the reflected light generated by the Rch and Gch phosphors 31R and 31G and the projection lens 8 is reflected by the dichroic mirror 16, and as shown in FIG. Come off. Since this reflected light does not reach the projection lens 8 and becomes unnecessary light and does not form an image on the screen, generation of a ghost image can be suppressed.

  According to the display device of the embodiment of the present invention, speckle noise generated by coherence of a laser light source is suppressed by reducing the light use efficiency by converting coherent light into light emission of a phosphor that is incoherent light. Can be removed.

  Further, according to the display device according to the embodiment of the present invention, the reflected light from the phosphor and the projection lens is separated from the optical path, so that a ghost image generated on the screen can be removed.

(Other embodiments)
Although the embodiments of the present invention have been described as described above, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In addition, of course, the present invention includes various embodiments that are not described here, such as a configuration in which the embodiment of the present invention and its modified examples are applied. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1,1R, 1G, 1B, 1A ... Optical unit 2 ... Reflection type light modulation element 3, 3R, 3G ... Fluorescent plate 4 ... Diffuser plate 5 ... X prism 6 ... Wheel 8 ... Projection lens 9 ... Screen 10 ... Light source unit 11 ... Condenser lens 12 ... Light tunnel 13, 15 ... Imaging lens 14 ... PBS
16 ... Dichroic mirror 21 ... Substrate 22 ... Reflective electrode 23 ... Light modulation layer 24 ... Transparent substrate 25 ... Drive unit 31R, 31G ... Phosphor 41 ... Diffusion film 60 ... Wheel substrate

Claims (4)

A light source that emits blue laser light;
A light modulation element that modulates blue laser light emitted from the light source in accordance with a video signal;
A phosphor that emits and emits light by blue laser light;
An imaging lens for imaging the blue laser light modulated by the light modulation element on the phosphor;
A dichroic mirror that is installed between the phosphor and the imaging lens so as to be inclined with respect to the optical path of the blue laser light, and transmits blue band light;
A display device comprising: a projection lens that projects an image formed on the phosphor by the imaging lens to the outside.   2. The display according to claim 1, wherein the phosphor is a phosphor that emits red light when excited by blue laser light or a phosphor that emits green light when excited by blue laser light. apparatus.   3. The display device according to claim 1, wherein the light modulation element is sequentially controlled so as to modulate blue laser light according to video signals of different channels every time. A flat wheel provided perpendicular to the optical path of the blue laser light;
The phosphor is provided on the surface of the wheel,
The display device according to claim 1, wherein the wheel rotates at a predetermined rotation number in synchronization with the blue laser beam.

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