JP2016145881A - Wavelength conversion element, illumination device, and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength conversion element, an illumination device, and a projector capable of improving efficiency for light utilization.SOLUTION: A polarization conversion element includes a substrate rotatable around a rotational shaft, and a plurality of quantum rods disposed on the substrate. Each of the plurality of quantum rods makes the substantially same angle to a radial direction of the substrate when viewed from a direction parallel to the rotational shaft.SELECTED DRAWING: Figure 2

Description

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

In recent years, lighting devices using phosphors are used in projectors. As such an illuminating device, there is known a technique for generating illumination light by irradiating a phosphor layer formed on a rotating substrate with excitation light to generate fluorescence, and synthesizing the fluorescence and excitation light. (For example, refer to Patent Document 1).
A technique for converting input light into linearly polarized light by using a quantum rod is also known (see, for example, Patent Document 2).

  The illumination light emitted from the illumination device of Patent Document 1 is non-polarized light. Therefore, a polarizing plate or a polarization conversion element is necessary, and there is a problem that light utilization efficiency is lowered.

JP 2012-137744 A Special table 2012-518808 gazette

Therefore, it is conceivable to improve the light utilization efficiency by combining the quantum rods as the phosphor layers of the illumination device and generating polarized illumination light.
However, when the illumination device and the quantum rod are combined, the direction of the quantum rod irradiated with the excitation light changes with time because the quantum rod rotates. Therefore, the polarization direction of the illumination light changes with time. In this case, since it is necessary to use the polarization conversion element or the polarizing plate, the light utilization efficiency is lowered.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a wavelength conversion element having high light utilization efficiency. Another object is to provide an illumination device that includes the wavelength conversion element and has high light use efficiency. Another object is to provide a projector that includes the lighting device and has high light use efficiency.

  According to the first aspect of the present invention, comprising a substrate rotatable around a rotation axis, and a plurality of quantum rods provided on the substrate, and when viewed from a direction parallel to the rotation axis, Each of the plurality of quantum rods is provided with a wavelength conversion element having substantially the same angle with respect to the radial direction of the substrate.

  According to the wavelength conversion element which concerns on a 1st aspect, even if a board | substrate rotates, the direction of the quantum rod with which excitation light is irradiated does not change. Therefore, even when the substrate rotates, the wavelength conversion element according to the first aspect can emit light in a certain polarization state. Therefore, when an unnecessary polarization component is cut using a polarizing plate to generate linearly polarized light, the loss of light can be reduced. Further, when the degree of polarization of light emitted from the wavelength conversion element is sufficiently high, a polarizing plate is not necessary. Thus, the light utilization efficiency can be greatly improved.

  According to the second aspect of the present invention, the light source that emits the light in the first wavelength band and the first aspect that receives the light in the first wavelength band and emits the light in the second wavelength band. There is provided an illuminating device comprising: a wavelength conversion element according to claim 1; and a rotation device that rotates the substrate around the rotation axis.

  The illumination device according to the second aspect can emit light in a certain polarization state as light in the second wavelength band.

  According to a third aspect of the present invention, the illumination device according to the second aspect, a light modulation device that forms image light by modulating illumination light from the illumination device according to image information, and the image light And a projection optical system for projecting.

  Since the projector according to the third aspect includes the illumination device according to the second aspect, it is possible to display brightly and with excellent image quality.

In the third aspect, the light modulation device has an image forming region including a plurality of pixels that form the image light, and a long side direction of each of the plurality of quantum rods is the first direction from the light source. In the irradiation region of the light of the wavelength band, it is preferable to match the long side direction or the short side direction of the image forming region.
The illumination device emits light polarized in the long side direction of the quantum rod. In general, the light transmission axis of the incident-side polarizing plate in the light modulation device using liquid crystal is set in the long side direction or the short side direction of the image forming region.
If this configuration is adopted, the polarization direction of the illumination light coincides with the light transmission axis of the incident-side polarizing plate, so that the illumination light can be efficiently incident on the light modulator and bright image light can be generated.

The figure which shows the structure of the optical system of a projector. The figure shown in order to demonstrate a rotation fluorescent screen. The conceptual diagram of the illumination light produced | generated by the fluorescence production | generation part. The conceptual diagram which showed the polarization direction of fluorescence.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

(projector)
An example of the projector according to the present embodiment will be described. The projector of this embodiment is a projection type image display device that displays a color image on a screen (projected surface) SCR. The projector uses three liquid crystal light modulation devices corresponding to red, green, and blue light. The projector uses a semiconductor laser that can obtain light with high luminance and high output as the light source of the illumination device.

FIG. 1 is a diagram illustrating a configuration of an optical system of a projector according to the present embodiment.
As shown in FIG. 1, the projector 1 includes an illumination device 100, a color separation light guide optical system 200, liquid crystal light modulation devices 400R, 400G, and 400B, a cross dichroic prism 500, and a projection optical system 600.

  Each of the liquid crystal light modulation devices 400R, 400G, and 400B modulates incident color light according to image information to form a color image. An incident side polarizing plate 401 is disposed on the light incident side of each of the liquid crystal light modulation devices 400R, 400G, and 400B, and an emission side polarizing plate 402 is disposed on the light emission side of each of the liquid crystal light modulation devices 400R, 400G, and 400B. ing.

  The illumination apparatus 100 includes a light source 10, an afocal optical system 11, a homogenizer optical system 12, a condensing optical system 20, a rotating fluorescent plate (wavelength conversion element) 30, a motor 50, a collimating optical system 60, a first lens array 120, a second A lens array 130 and a superimposing lens 150 are provided.

The light source 10 includes a plurality of semiconductor lasers 10A that emit blue light (emission intensity peak: about 445 nm) B as light in a first wavelength band composed of laser light as excitation light. The plurality of semiconductor lasers 10A are arranged in an array in one plane orthogonal to the illumination optical axis 100ax.
The light source 10 may be a semiconductor laser that emits blue light having a wavelength other than 445 nm (for example, 460 nm).
In the present embodiment, the blue light B emitted from the light source 10 is linearly polarized light in a predetermined direction.

The afocal optical system 11 includes, for example, a convex lens 11a and a concave lens 11b. The afocal optical system 11 reduces the diameter of the light beam of blue light emitted from the light source 10 (light beam composed of a plurality of laser beams). Thus, since the afocal optical system 11 reduces the beam diameter of the excitation light, a small condensing optical system 20 can be used. Therefore, the illuminating device 100 provided with the condensing optical system 20 can be reduced in size and weight.
A collimator optical system may be disposed between the afocal optical system 11 and the light source 10 to convert the excitation light incident on the afocal optical system 11 into a parallel light beam.

  The homogenizer optical system 12 includes, for example, a first multi-lens array 12a and a second multi-lens array 12b. The homogenizer optical system 12 converts the light intensity distribution of the excitation light into a uniform state (so-called top hat distribution) in cooperation with the condensing optical system 20.

  Specifically, the homogenizer optical system 12 cooperates with the condensing optical system 20 to emit a plurality of small light beams emitted from the plurality of small lenses of the first multi-lens array 12a on the fluorescence generation unit 42 (described later). To overlap each other. Thereby, the light intensity distribution of the blue light B irradiated onto the fluorescence generation unit 42 is set to a uniform state (so-called top hat distribution).

  The condensing optical system 20 includes a first lens 22 and a second lens 24. The condensing optical system 20 is disposed in the optical path from the homogenizer optical system 12 to the rotating fluorescent plate 30 and makes blue light (excitation light) enter the rotating fluorescent plate 30 in a substantially condensed state. In the present embodiment, each of the first lens 22 and the second lens 24 is a convex lens.

FIG. 2 is a view for explaining the rotating fluorescent plate according to the embodiment.
As shown in FIGS. 1 and 2, the rotating fluorescent plate 30 includes a disc (substrate) 40 that can be rotated around a predetermined rotation axis O by a motor 50, and a fluorescence generation unit 42 provided on the disc 40. And have.

  The fluorescence generation unit 42 is provided along the circumferential direction of the disc 40. As will be described later, the rotating fluorescent plate 30 emits yellow fluorescence (light in the second wavelength band) Y including red light and green light toward the side opposite to the side on which the blue light B is incident.

  The disc 40 is made of a material that transmits the blue light B. As a material of the disc 40, for example, quartz glass, quartz, sapphire, optical glass, transparent resin, or the like can be used.

  In the present embodiment, the blue light B from the light source 10 enters the fluorescence generation unit 42 from the disk 40 side, and a part of the incident blue light B passes through the fluorescence generation unit 42. A dichroic film (not shown) that transmits the blue light B and reflects the fluorescence Y is provided between the fluorescence generator 42 and the disc 40.

  The blue light B forms a spot BS on the fluorescence generation unit 42. The position of the spot BS is spatially fixed, and the center of the spot BS coincides with the illumination optical axis 100ax of the light source 10. As the disc 40 rotates, the fluorescence generation unit 42 located in the spot BS sequentially changes.

  By sequentially changing the fluorescence generation part 42 located in the spot BS, damage caused by heat of the fluorescence generation part 42 due to the irradiation of the blue light B is reduced.

  The fluorescence generation part 42 is formed, for example, by mixing and stretching a plurality of quantum rods 52 in a binder 51 made of an organic film. Each quantum rod 52 is a rod-like particle of a compound semiconductor (for example, GaAs, GaN, etc.) having a size of several n to several tens of nm, for example.

In general, the quantum rod 52 has a wavelength conversion function of emitting light of a different color when irradiated with light.
The quantum rod 52 has a different wavelength conversion function depending on its size. That is, the quantum rod 52 generates fluorescence of a color corresponding to the size.

The plurality of quantum rods 52 form substantially the same angle with respect to the radial direction of the disc 40 when viewed from a direction parallel to the rotation axis O (upper surface direction of the disc 40). For example, in the present embodiment, the plurality of quantum rods 52 are arranged so that the long side direction thereof is directed in a direction orthogonal to the radial direction of the disc 40.
Here, the radial direction of the disc 40 means a direction connecting the rotation center and the quantum rod 52.

  Therefore, even if the fluorescence generation unit 42 located in the spot BS changes with the rotation of the disc 40, the direction (orientation direction) of the quantum rod 52 included in the spot BS does not change and is always the same. The direction (the direction perpendicular to the radial direction of the disc 40) is directed.

FIG. 3 is a conceptual diagram of illumination light generated by the fluorescence generator 42.
As shown in FIG. 3, each quantum rod 52 included in the fluorescence generation unit 42 converts part of the blue light B from the light source 10 into yellow fluorescence Y.

  On the other hand, in the binder 51 in the fluorescence generation part 42, the remaining part of the blue light B passes through and is emitted to the outside. The binder 51 does not affect the polarization direction of the blue light B regardless of whether or not the disk 40 is rotated.

  In the present embodiment, the white light W is obtained by combining the component of the blue light B from the light source 10 that has passed through the fluorescence generator 42 and the yellow fluorescence Y from the quantum rod 52.

  FIG. 4 is a conceptual diagram showing the polarization direction of fluorescence Y. In FIG. 4, the light transmission axis 401a of the incident side polarizing plate 401 is also illustrated.

Since the quantum rod 52 of the present embodiment has a rod-like nanocrystal, the fluorescence Y polarized in the long side direction of the quantum rod 52 can be emitted as shown in FIG.
Note that the double arrows in FIG. 4 conceptually show the polarization directions of the fluorescence Y and the blue light B.

  In this embodiment, since the direction of the quantum rod 52 does not change in the spot BS of the blue light B as described above, the polarization direction of the fluorescence Y changes even when the disk 40 is rotating. It is prevented.

The blue light B is linearly polarized light polarized in a predetermined direction. Specifically, the polarization direction of the blue light B coincides with the long side direction of the quantum rod 52. For this reason, the polarization directions of the blue light B and the fluorescence Y coincide with each other.
In the present embodiment, the white light W as a whole is composed of linearly polarized light components polarized in one direction.

  As described later, the white light W is separated into red light, green light, and blue light by the color separation light guide optical system 200, and then the liquid crystal light modulation device 400R to which the red light, green light, and blue light respectively correspond. , 400G, 400B.

  Each of the liquid crystal light modulation devices 400R, 400G, and 400B has an image forming area (image display area) including a plurality of pixels that form image light. In FIG. 4, the image forming areas are image forming areas 4R1, 4G1, and 4B1, respectively, and are virtually overlapped with the spot BS in a planar manner.

  As shown in FIG. 4, the image forming areas 4R1, 4G1, and 4B1 are each rectangular. Conventionally, in the liquid crystal light modulation device, the light transmission axis 401a of the incident side polarizing plate 401 coincides with one of the short side direction and the long side direction of the image forming regions 4R1, 4G1, and 4B1.

  In the present embodiment, the long side direction of each of the plurality of quantum rods 52 in the spot BS is matched with the short side direction of each of the image forming regions 4R1, 4G1, and 4B1, for example. In each of the image forming regions 4R1, 4G1, and 4B1, it is assumed that the light transmission axis 401a of the incident side polarizing plate 401 is set in the short side direction.

  The long side direction of the quantum rod 52 coincides with the polarization direction of the white light W. Therefore, in the present embodiment, the polarization directions of the red light, the green light, and the blue light generated by separating the white light W are changed to the light transmission axis 401a of the incident-side polarizing plate 401 in the image forming regions 4R1, 4G1, and 4B1. It is possible to match each direction.

  Thereby, red light, green light, and blue light efficiently enter the image forming regions 4R1, 4G1, and 4B1, respectively. Therefore, it is possible to efficiently generate bright image light.

  In addition, the light transmission axis of the incident side polarizing plate in each of the image forming regions 4R1, 4G1, and 4B1 may be set in the long side direction. In this case, the long side direction of the quantum rod 52 is the same as that of the disk 40 in FIG. What is necessary is just to set to the radial direction (long-side direction of image formation area 4R1, 4G1, 4B1).

  Returning to FIG. 1, the collimating optical system 60 includes a first collimating lens 62 and a second collimating lens 64, and makes the light from the rotating fluorescent plate 30 substantially parallel. The first collimating lens 62 and the second collimating lens 64 are convex lenses.

  The first lens array 120 has a plurality of first small lenses 122 for dividing the light from the collimating optical system 60 into a plurality of partial light beams. The plurality of first small lenses 122 are arranged in a matrix in a plane orthogonal to the illumination optical axis 100ax.

  The second lens array 130 has a plurality of second small lenses 132 corresponding to the plurality of first small lenses 122 of the first lens array 120. The second lens array 130 forms an image of each first small lens 122 of the first lens array 120 together with the superimposing lens 150 in the vicinity of the image forming area of the liquid crystal light modulators 400R, 400G, and 400B. The plurality of second small lenses 132 are arranged in a matrix in a plane orthogonal to the illumination optical axis 100ax.

  By the way, conventionally, in order to efficiently use illumination light, light emitted from the rotating fluorescent plate 30 has been converted into linearly polarized light. Therefore, for example, a polarization conversion element is installed between the second lens array 130 and the superimposing lens 150.

  On the other hand, in this embodiment, since illumination light (white light W) is linearly polarized light, it is not necessary to install a polarization conversion element. Thereby, compared with the structure which installs the conventional polarization conversion element, an apparatus structure is simplified and size reduction and cost reduction can be achieved. Further, there is no light loss due to the polarization conversion element.

  The superimposing lens 150 collects the partial light beams from the second lens array 130 and superimposes them in the vicinity of the image forming areas of the liquid crystal light modulation devices 400R, 400G, and 400B. The first lens array 120, the second lens array 130, and the superimposing lens 150 constitute an integrator optical system that makes the in-plane light intensity distribution of the light from the rotating fluorescent plate 30 uniform.

The color separation light guide optical system 200 includes dichroic mirrors 210 and 220, reflection mirrors 230, 240 and 250, and relay lenses 260 and 270. The color separation light guide optical system 200 separates light from the illumination device 100 into red light, green light, and blue light, and the liquid crystal light modulation devices 400R, 400G, and 400B that respectively correspond to red light, green light, and blue light. To guide the light.
Condensing lenses 300R, 300G, and 300B are disposed between the color separation light guide optical system 200 and the liquid crystal light modulation devices 400R, 400G, and 400B.

The dichroic mirror 210 is a dichroic mirror that transmits a red light component and reflects a green light component and a blue light component.
The dichroic mirror 220 is a dichroic mirror that reflects a green light component and transmits a blue light component.
The reflection mirror 230 is a reflection mirror that reflects a red light component.
The reflection mirrors 240 and 250 are reflection mirrors that reflect blue light components.

The red light that has passed through the dichroic mirror 210 is reflected by the reflecting mirror 230, passes through the condenser lens 300R, and enters the image forming area of the liquid crystal light modulation device 400R for red light.
The green light reflected by the dichroic mirror 210 is further reflected by the dichroic mirror 220, passes through the condenser lens 300G, and enters the image forming area of the liquid crystal light modulation device 400G for green light.
The blue light that has passed through the dichroic mirror 220 passes through the relay lens 260, the incident-side reflecting mirror 240, the relay lens 270, the exit-side reflecting mirror 250, and the condensing lens 300B to form an image of the liquid crystal light modulation device 400B for blue light. Incident into the area.

  The cross dichroic prism 500 combines the image lights emitted from the liquid crystal light modulation devices 400R, 400G, and 400B to form a color image.

  The cross dichroic prism 500 has a substantially square shape in plan view in which four right-angle prisms are bonded together, and a dielectric multilayer film is formed on a substantially X-shaped interface in which the right-angle prisms are bonded together.

  The color image emitted from the cross dichroic prism 500 is enlarged and projected by the projection optical system 600 to form an image on the screen SCR.

  As described above, according to the present embodiment, the direction of the quantum rod 52 does not change greatly in the spot BS of the blue light B even when the disk 40 rotates. Therefore, even when the disc 40 rotates, the rotating fluorescent plate 30 emits the fluorescence Y having a substantially constant polarization state. Therefore, as in the present embodiment, when an unnecessary polarization component is cut using the incident-side polarizing plate to convert the fluorescence Y into linearly polarized light, the polarization direction of the fluorescence Y is temporally between 0 ° and 90 °. No large optical loss occurs as in the case of fluctuation. In addition, when the polarization degree of the fluorescence Y is high to an acceptable level, the incident side polarizing plate can be omitted, so that there is no light loss due to the incident side polarizing plate. Thus, according to this embodiment, the fluorescence Y can be used efficiently. Therefore, the projector 1 of this embodiment can display a bright image with excellent quality.

  Further, since the rotating fluorescent plate 30 emits the fluorescence Y having a substantially constant polarization state, even if the polarization conversion element is omitted, the polarization direction of the fluorescence Y varies temporally between 0 ° and 90 °. No significant optical loss occurs. Therefore, when the polarization conversion element is omitted, the apparatus configuration is simplified, and downsizing and cost reduction can be achieved.

  In addition, this invention is not necessarily limited to the thing of the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.

In the said embodiment, although the case where the long side direction of the quantum rod 52 was set to the direction orthogonal to the radial direction of the disc 40 was mentioned as an example, this invention is not limited to this.
For example, the long side direction of the quantum rod 52 may be set in the radial direction of the disc 40. In this case, the plurality of quantum rods 52 are arranged radially with respect to the center of the disc 40.

  Alternatively, the long side direction of the quantum rod 52 may be set in a direction intersecting the radial direction (a direction other than orthogonal). The direction of the light transmission axis of the incident side polarizing plate may be adjusted as appropriate according to the direction of the long side direction of the quantum rod 52.

Moreover, in the said embodiment, although the transmissive | pervious type | mold thing with which the incident direction of the blue light B and the injection | emission direction of fluorescence Y corresponded as an example as the rotation fluorescent plate 30, this invention is not limited to this.
For example, as the rotating fluorescent plate, a reflection type plate in which the incident direction of the blue light B and the emission direction of the fluorescence Y are opposite may be used. In this case, the rotating fluorescent plate may be formed by forming the fluorescence generating unit 42 including the quantum rod 52 on a disc made of a metal plate having light reflectivity.

Moreover, although the case where the incident side polarizing plate was installed in the front | former stage of each liquid crystal light modulation device 400R, 400G, 400B was mentioned as an example in the said embodiment, this invention is not limited to this.
For example, when the white light W is linearly polarized light with a high degree of polarization, the incident side polarizing plate may be omitted.

  In the above-described embodiment, the projector 1 including the three liquid crystal light modulation devices 400R, 400G, and 400B is illustrated. However, the projector 1 can be applied to a projector that displays a color image with one liquid crystal light modulation device. A digital mirror device may be used as the light modulation device.

  Moreover, although the example which mounted the illuminating device by this invention in the projector was shown in the said embodiment, it is not restricted to this. The lighting device according to the present invention can also be applied to lighting fixtures, automobile headlights, and the like.

B: Blue light (light in the first wavelength band), Y: Fluorescence (light in the second wavelength band), BS: Spot (irradiation area of light in the first wavelength band), 1 ... Projector, 4R1, 4G1 , 4B1 ... image forming region, 10 ... light source, 30 ... rotating fluorescent plate (wavelength conversion element), 40 ... disc (substrate), 52 ... quantum rod, 100 ... illumination device, 400R, 400G, 400B ... liquid crystal light modulator ( Light modulator).

Claims (4)

A substrate rotatable around a rotation axis;
A plurality of quantum rods provided on the substrate,
When viewed from a direction parallel to the rotation axis, each of the plurality of quantum rods forms substantially the same angle with respect to the radial direction of the substrate. A light source that emits light in a first wavelength band;
2. The wavelength conversion element according to claim 1, which receives the light in the first wavelength band and emits light in a second wavelength band.
A rotating device that rotates the substrate around the rotation axis. A lighting device according to claim 2;
A light modulation device that forms image light by modulating illumination light from the illumination device according to image information; and
A projection optical system that projects the image light. The light modulation device includes an image forming region including a plurality of pixels that form the image light,
The long side direction of each of the plurality of quantum rods coincides with a long side direction or a short side direction of the image forming region in an irradiation region of light in the first wavelength band from the light source. 3. The projector according to 3.

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