JP2022112217A - Light source device and image projection device - Google Patents

Abstract

To provide a light source device capable of generating bright light.SOLUTION: A light source device (100) comprises a light source unit (10) for emitting light of a first color, a wavelength conversion element (9) configured to convert the light of the first color into light of a second color, and a retroreflective optical element (7) having a first sub area for transmitting the light of the second color and a second sub area for reflecting the light of the second color. The maximum light density of the light of the first color at the wavelength conversion element is greater than 30 W/mm2.SELECTED DRAWING: Figure 1

Description

The present invention relates to a light source device and an image projection device.

2. Description of the Related Art Conventionally, there has been known an image projection apparatus (projector) in which an image display element is irradiated with a light flux generated from a light source, the light flux is modulated by the image display element according to an input video signal, and the light flux is projected by a projection optical system. there is Japanese Unexamined Patent Application Publication No. 2002-200003 discloses an image projection apparatus that uses fluorescent light generated by exciting a wavelength conversion element (phosphor) with light from a laser diode (LD) as illumination light.

JP 2014-209184 A

The image projection apparatus disclosed in Patent Document 1 can increase the brightness of the projected image by increasing the number and output of the LDs. However, when the amount of excitation light incident on the wavelength conversion element increases, the conversion efficiency from excitation light to fluorescent light decreases due to the effect of luminance saturation of the wavelength conversion element. In addition, the excitation light that has not been converted by the wavelength conversion element returns to the LD, raises the temperature of the LD, and reduces the luminous efficiency of the LD.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a light source device and an image projection device capable of generating bright light.

A light source device as one aspect of the present invention includes a light source unit that emits a first color light, a wavelength conversion element that converts the first color light into a second color light, and a first light source that transmits the second color light. a retrooptical element having a partial area and a second partial area that reflects the second color light, wherein the maximum optical density of the first color light in the wavelength conversion element is greater than 30 (W/mm ² ) is also big.

Other objects and features of the invention are illustrated in the following examples.

According to the present invention, it is possible to provide a light source device and an image projection device capable of generating bright light.

1 is a configuration diagram of an image projection apparatus in Example 1. FIG. 1 is a configuration diagram of a retrooptical element in Example 1. FIG. 1 is a configuration diagram of a phosphor wheel in Example 1. FIG. 4A and 4B are schematic diagrams of fluorescent light beams before and after they enter the retrooptic element in Example 1. FIG. FIG. 10 is a configuration diagram of an image projection apparatus in Example 2; FIG. 11 is a configuration diagram of an image projection apparatus in Example 3; 10A and 10B are schematic diagrams of fluorescent light beams before and after they enter and exit the retrooptic element in Example 3. FIG. FIG. 11 is a configuration diagram of a retro-optical element in Example 3; FIG. 5 is a diagram showing the amount of improvement in illumination efficiency by the retro-optical element in each example.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, an image projection apparatus (projector) 200 according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of an image projection apparatus 200. As shown in FIG. The image projection device 200 has a light source device 100 , an illumination optical system 150 , a color separation/combination system 160 , an image display element 24 and a projection lens (projection optical system) 25 .

In the light source device 100, an LD unit (light source section) 10 has a plurality of LDs (laser diodes) 1 and a plurality of collimator lenses 2, and emits blue light (first color light). Blue light from the LD unit 10 is compressed by the first lens 3 with positive power and the second lens 4 with negative power. The first lens 3 and the second lens 4 constitute an afocal optical system. The compressed blue light is split into a plurality of luminous fluxes by the lens array 5, transmitted through the dichroic mirror 6 and the retro-optical element (retro-mirror) 7, and passed through the first collimator lens (condensing means) 8 to the phosphor wheel ( The light is focused on the wavelength conversion element 9 . A first collimator lens 8 condenses the blue light onto a predetermined area of the phosphor wheel 9 . The dichroic mirror 6 has the characteristic of transmitting blue light and reflecting green and red light. In this embodiment, the retrooptical element 7 is arranged in the optical path between the illumination optics 150 and the phosphor wheel 9 .

Next, the configuration of the retrooptical element 7 will be described with reference to FIG. FIG. 2 is a configuration diagram of the retrooptical element 7. As shown in FIG. The retrooptic element 7 has a region (first partial region) 7A and a region (second partial region) 7B. The region 7A has a length L1 in a first direction (x direction) and a length L2 in a second direction (y direction) perpendicular to the first direction. The region 7A is a region (a region that transmits at least the second color light) having characteristics of transmitting visible light (blue light, green light, and red light). The region 7B is a region (reflects at least the second color light) that has the property of reflecting visible light or fluorescent light (green light and red light). Note that the retro-optical element 7 may be formed by chemically etching the substrate to make the region 7A hollow.

Next, the configuration of the phosphor wheel 9 will be described with reference to FIG. FIG. 3 is a configuration diagram of the phosphor wheel 9. As shown in FIG. The phosphor wheel 9 has a substrate 9A with high thermal conductivity and a transparent substrate 9B that transmits light, and converts the first color light (blue light) into the second color light (green light and red light, ie, fluorescent light). ). The substrate 9A is circumferentially coated with the phosphor 9C, and a reflective film is deposited between the phosphor 9C and the substrate 9A. Further, the center of the phosphor wheel 9 is fixed to the drive shaft of the motor, and the phosphor wheel 9 rotates about the rotating shaft. A metal substrate such as aluminum or copper or a crystal substrate such as sapphire can be used for the substrate 9A. The substrate 9B can be glass, transparent ceramics, resin, or a crystal substrate such as sapphire. The phosphor 9C may be a material that absorbs excitation light and emits fluorescence, such as quantum dots and quantum rods.

Since the phosphor wheel 9 is rotating, blue light is incident on the substrates 9A and 9B at a certain rate of time. Most of the blue light incident on the substrate 9A is converted into fluorescent light (green light+red light). Fluorescent light from the phosphor 9C is collimated by the first collimator lens (collimating means) 8 and enters the retrooptical element 7. As shown in FIG. The fluorescent light incident on the region 7B is reflected and returned to the phosphor 9C of the phosphor wheel 9. FIG. Part of the fluorescent light returned to the phosphor 9C is reabsorbed by the phosphor, but most of the light is scattered and reflected.

Next, with reference to FIGS. 4(a) and 4(b), the luminous flux of the fluorescent light before entering and after exiting the retrooptical element 7 will be described. 4A is a schematic diagram of the fluorescent light flux before entering the retrooptic element 7, and FIG. 4B is a schematic diagram of the fluorescent light flux after exiting the retrooptic element 7. FIG. As shown in FIGS. 4A and 4B, the area S of the luminous flux before entering the retrooptic element 7 (the luminous flux immediately before incidence) is the area S of the luminous flux after exiting the retrooptic element 7 (the luminous flux immediately after exiting the retrooptic element 7). ) is reduced to the area S′. Therefore, by arranging the retrooptical element 7, the area of the luminous flux can be reduced without lowering the illumination efficiency. The fluorescent light that has passed through the area 7A is reflected by the dichroic mirror 6 and guided to the illumination optical system 150. FIG.

The illumination optical system 150 has a first fly-eye lens 19, a second fly-eye lens 20, and a condenser lens 21, and illuminates the image display element 24 with illumination light. The image display device 24 is a device (digital micromirror device: DMD) having micromirrors corresponding to pixels, and modulates the illumination light by changing the reflection direction of the illumination light with the micromirrors. However, this embodiment is not limited to this, and the image display element 24 may be a reflective liquid crystal panel or a transmissive liquid crystal panel.

The color separation/combination system 160 has a TIR prism 22 and a dichroic prism (color separation means) 23 . The TIR prism 22 is composed of a first prism 22A and a second prism 22B, which are bonded together with an air gap of several tens of μm at the interface. The dichroic prism 23 has characteristics of transmitting green light and reflecting blue and red light. Light entering the color separation/combination system 160 from the illumination optical system 150 is totally reflected by the TIR prism 22 and separated into green light and red light by the dichroic prism 23 . Green light illuminates the first image display element 24A and red light illuminates the second image display element 24B. The light modulated by the first image display element 24A is transmitted through the dichroic prism 23 and the TIR prism 22 and guided to the projection lens 25. FIG. The light guided to the projection lens 25 is enlarged and projected onto a screen (projection target surface) (not shown). The red light modulated by the second image display element 24B is reflected by the dichroic prism 23, and enlarged and projected onto a screen (not shown) on the same principle as green light.

The blue light incident on the substrate 9B of the phosphor wheel 9 passes through the substrate 9B and is focused on the diffuser plate 15 via the first relay lens 11 and the second relay lens 14 . A first mirror 12 and a second mirror 13 are arranged to fold the optical path. The blue light diffused by the diffusion plate 15 is reflected by the third mirror 16 that bends the optical path, collimated by the second collimator lens 17 and guided to the dichroic mirror 6 . The blue light guided to the dichroic mirror 6 passes through the dichroic mirror 6 and enters the color separation/combination system 160 via the illumination optical system 150 . The blue light incident on the color separation/combination system 160 is reflected by the dichroic prism 23 and illuminates the second image display element 24B. The blue light modulated by the second image display element 24B is guided to a screen (not shown) on the same principle as red light.

Since the substrate 9B of the phosphor wheel 9 is provided for transmitting the incident blue light, the substrate 9B may not be provided. Alternatively, the diffusion plate 15 may be arranged on the substrate 9B. Since the unconverted blue light from the phosphor wheel 9 is collimated by the first collimating lens 8 , a retro-optical element 7 may be arranged between the lens array 5 and the dichroic mirror 6 .

Next, conditions that the retro-optical element 7 preferably satisfies in this embodiment will be described. The etendue of the illumination optical system 150 can be expressed by the following equation (1).

E=π×A/(2×F) ² (1)
In equation (1), A (mm ² ) is the area of the effective region of the image display element 24 and F is the F value of the projection lens 25 . Since fluorescent light is emitted from the phosphor 9C at a uniform angle, if the etendue of the illumination optical system 150 is determined, the area B (mm ² ) of the excitation light that can be captured can be calculated. When taking in all the light beams, the collimator lens must have an F-number of 0.5. Therefore, the relationship between the etendue E and the area B of the illumination optical system 150 is E>π×B/(2×0.5)=π×B, that is, B<E/π.

However, the image of the excitation light on the phosphor 9C is blurred due to aberration of the optical system, and the image spreads due to the scattering of the fluorescence light inside the phosphor 9C. (2).

B=E/4 (2)
Therefore, when the optical density of the excitation light in the phosphor 9C in the optimum design is D (W/mm ² ), the optical density D can be expressed by the following formula (3).

D=4P/E (3)
In formula (3), P is the energy (W) of the excitation light that excites the phosphor 9C. When the light density of the excitation light in the phosphor 9C is low, there is little reduction in efficiency due to luminance saturation in the phosphor 9C, so there is no need for retroreflection by the retroreflecting optical element 7. FIG. On the other hand, when the optical density of the excitation light increases, efficiency decreases significantly due to brightness saturation, so it is preferable to satisfy the following conditional expressions (4) and (5).

30≦D≦180 (4)
0.2-0.001×D≦R≦0.8 (5)
R = (SS')/S
Here, S (mm ² ) is the area of the luminous flux immediately before entering the retrooptic element 7 and S′ (mm ² ) is the area of the luminous flux immediately after exiting the retrooptic element 7 . R is the recursion rate. FIG. 9 is a diagram showing the amount of improvement in illumination efficiency by the retrooptical element 7, and shows the relationship between the retroreflection rate R (vertical axis) of fluorescent light, the light density D (horizontal axis), and the amount of improvement. It can be seen that the higher the light density D, the higher the improvement effect due to recursion.

If the lower limit of the conditional expression (4) is exceeded, the effect of the present embodiment cannot be obtained because the reduction in efficiency due to luminance saturation is small. On the other hand, if the upper limit of conditional expression (4) is exceeded, the optical density D is too high, and the temperature may further rise due to the effect of the retroreflected fluorescent light, which may cause a problem with the durability of the phosphor 9C.

If the lower limit of conditional expression (5) is exceeded, the effect of improving efficiency by recursion cannot be obtained. On the other hand, if the upper limit of the conditional expression (5) is exceeded, the amount of retroreflected light to the phosphor 9C will increase too much, which may cause a problem with the durability of the phosphor 9C.

In this embodiment, in order to substantially satisfy each of the above conditional expressions, it is necessary to set the maximum optical density of the excitation light on the phosphor wheel 9 to be greater than 30 (W/mm ² ).

More preferably, the numerical ranges of conditional expressions (4) and (5) are set so as to satisfy the following conditional expressions (4a) and (5a), respectively.

25R+35≦D≦150 (4a)
0.25−0.001×D≦R≦0.6 (5a)
In this embodiment, the length L1 of the region 7A of the retrooptic element 7 in the first direction and the length L2 in the second direction orthogonal to the first direction satisfy the following conditional expression (6): is preferred.

1.1×L2≦L1 (6)
In this embodiment, the first direction is the x-direction and the second direction is the y-direction, as shown in FIG. Since TIR prisms, dichroic mirrors, polarizing beam splitters, etc. have angular characteristics, they can be used with high efficiency by reducing the angular distribution of light rays in the color separation cross section of light. In this embodiment, the plane formed by the normal to the color separation section of the dichroic prism 23 and the optical axis is parallel to the second direction (y direction). Thus, by making the y direction of the region 7A more retrograde, the TIR prism 22 and the dichroic prism 23 can be used with high efficiency.

More preferably, the numerical range of conditional expression (6) is set so as to satisfy the following conditional expression (6a).

1.2×L2≦L1 (6a)
Here, consider an optical system in which the image of the fluorescent light of the phosphor 9C is collimated by the first collimator lens 8, reflected by the retroreflecting optical element 7, and re-imaged on the phosphor 9C. In this case, by arranging the retro-optical element 7 in the vicinity of the pupil position of the first collimator lens 8, the telecentric optical system can be made, so that the retro-reflection efficiency can be improved. When the air conversion distance from the principal point of the first collimator lens 8 to the retro-optical element 7 is da, and the focal length of the first collimator lens 8 is fc, it is preferable to satisfy the following conditional expression (7). .

0.5≦da/fc≦1.5 (7)
More preferably, the numerical range of conditional expression (7) is set so as to satisfy the following conditional expression (7a).

0.75≦da/fc≦1.25 (7a)

Next, with reference to FIG. 5, an image projection apparatus according to Embodiment 2 of the present invention will be described. FIG. 5 is a configuration diagram of the optical system of the image projection apparatus of this embodiment.

The LD unit (light source section) 50 has a plurality of LDs (laser diodes) 51 and a plurality of collimator lenses 52 . Blue light from the LD unit 50 is condensed onto a phosphor wheel (wavelength conversion element) 54 by a condensing lens 53 . The basic structure of the phosphor wheel 54 is the same as that of the first embodiment (FIG. 3), but since the blue light must be transmitted through the substrate, sapphire or the like has high thermal conductivity and high visible light transmittance. A substrate is used.

Fluorescent light and blue light from phosphor wheel 54 are collimated by collimator lens 55 and enter retrooptic element 56 . The basic configuration of the retrooptical element 56 is the same as that of the first embodiment (FIG. 2). As in the first embodiment, a portion of the fluorescent light incident on the retroreflecting optical element 56 is returned to the phosphor of the phosphor wheel 54 . The light that has passed through the retro-optical element 56 is guided to the illumination optical system and projected via the color separation/combination system and projection lens.

Next, with reference to FIG. 6, an image projection apparatus according to Embodiment 3 of the present invention will be described. FIG. 6 is a configuration diagram of the optical system of the image projection apparatus of this embodiment.

Blue light from a plurality of LD units (light source section) 61 is condensed onto a phosphor substrate (wavelength conversion element) 63 by a plurality of condensing lenses 62 . Accordingly, a plurality of blue light source images are formed on the phosphor substrate 63 . Fluorescent light emitted from a plurality of light source images is collimated by a plurality of collimator lenses 64 and enters a retrooptical element 65 . The basic configuration of the retro-optical element 65 is the same as in Example 1 (FIG. 2). A portion of the fluorescent light that has entered the retrooptical element 65 is returned to the phosphor substrate 63 .

FIG. 7A is a schematic diagram of the fluorescent light flux just before (before incidence) entering the retrooptic element 65, and FIG. 7B is a schematic diagram of the fluorescent light flux immediately after being emitted from the retrooptic element 65 (after emission). It is a diagram. By arranging the retro-optical element 65, the area of the luminous flux can be reduced from S to S' without significantly deteriorating the illumination efficiency. The light that has passed through the retro-optical element 65 is guided to the illumination optical system and projected through the color separation/combination system and projection lens.

In this embodiment, the configuration for retroreflecting the peripheral portion of a plurality of collimated fluorescent light beams has been described. ) 65A may be a configuration having multiple regions separated from each other. That is, the retrooptical element 65 may have a plurality of regions (first partial regions) 65A and regions (second partial regions) 65B.

According to each embodiment, it is possible to provide a light source device and an image projection device capable of generating bright light.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist.

7 Retrooptical element 9 Phosphor wheel (wavelength conversion element)
10 LD unit (light source)
100 light source device

Claims (9)

a light source unit that emits a first color light;
a wavelength conversion element that converts the first color light into a second color light;
a retro-optical element having a first partial area that transmits the second colored light and a second partial area that reflects the second colored light;
A light source device, wherein the maximum light density of the first color light in the wavelength conversion element is greater than 30 (W/mm ² ). When the length of the first partial region of the retrooptic element in the first direction is L1 and the length in the second direction perpendicular to the first direction is L2,
1.1×L2≦L1
2. The light source device according to claim 1, wherein the following conditional expression is satisfied. 3. A light source device according to claim 1, wherein the first partial area of the retrooptic element comprises a plurality of areas separated from each other. 4. The light source device according to any one of claims 1 to 3, further comprising a collimator lens that converges the first color light onto the wavelength conversion element and parallelizes the second color light. A light source device according to claim 1 or 2;
an image display element;
and an illumination optical system for illuminating the image display device. P is the energy (W) of the excitation light that excites the wavelength conversion element, A is the area (mm ² ) of the effective region of the image display element, F is the F value of the projection lens, and F is the luminous flux immediately before the retro-optical element. When the area is S and the area of the luminous flux immediately after the retrooptical element is S',
30≤D≤180
0.2-0.001×D≦R≦0.8
R = (SS')/S
D = 4P/E
E=π×A/(2×F) ²
6. The image projection apparatus according to claim 5, wherein the following conditional expression is satisfied. 7. The image projection apparatus according to claim 5, wherein said retro-optical element is arranged in an optical path between said illumination optical system and said wavelength conversion element. 8. The image projection apparatus according to any one of claims 5 to 7, further comprising color separation means for separating said second color light incident on said illumination optical system. When the length of the first partial region of the retrooptic element in the first direction is L1 and the length in the second direction perpendicular to the first direction is L2,
1.1×L2≦L1
satisfies the following conditional expression,
9. The image projection apparatus according to claim 8, wherein a plane formed by a normal line of a color separation section of said color separation means and an optical axis is parallel to said second direction.

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