JP2018106087A - Light source device and image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce rays of light returning toward a light source, of rays of light emitted from the light source to an optical characteristic conversion element.SOLUTION: A light source device 1 comprises, in order from a light source 303, a polarization layer 401 that transmits first polarized light having a first polarization direction and reflects second polarized light having a second polarization direction different from the first polarization direction; a phase difference layer 402; and an optical characteristic conversion element 404 that generates characteristic conversion light having a different characteristic from that of incident light.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a light source device used in an image projection apparatus (hereinafter referred to as a projector).

  As a light source device for a projector, an apparatus including a laser light source and a light characteristic conversion element such as a phosphor is used. In Patent Document 1, a phosphor is irradiated with blue laser light as excitation light, and a part of the wavelength of the excitation light is converted by the phosphor to generate yellow fluorescent light. A light source device that emits white light combined with light is disclosed. And in this light source device, in order to improve the utilization efficiency of the fluorescent light, a structure that guides the fluorescent light toward the laser light source in the original emission direction by using a dichroic film that transmits the excitation light and reflects the fluorescent light Is disclosed.

JP 2012-137705 A

  In the light source device as described above, in order to further improve the light utilization efficiency and stabilize the color of the emitted light, less excitation light returns to the laser light source side without being converted into fluorescent light by the phosphor. There is a need to.

  The present invention provides a light source device and a projector using the light source device, which can reduce the light returning to the light source side among the light irradiated from the light source to the light characteristic conversion element.

  The light source device according to one aspect of the present invention transmits, in order from the light source side, the first polarized light having the first polarization direction and the second polarization direction different from the first polarization direction. It has a polarizing layer that reflects polarized light, a retardation layer, and an optical characteristic conversion element that generates characteristic conversion light having different characteristics from incident light.

  Note that an image projection apparatus using the light source device also constitutes another aspect of the present invention.

  According to the present invention, it is possible to reduce the light that returns to the light source side from the light irradiated to the light characteristic conversion element from the light source, and it is possible to improve the light utilization efficiency and to stabilize the color of the emitted light. it can. And by using this light source device for an image projection device, an image with stable brightness and color can be projected.

1 is a diagram illustrating a configuration of a projector including a light source device that is Embodiment 1 of the present invention. FIG. FIG. 3 is a cross-sectional view illustrating the configuration of the light source device according to the first embodiment. FIG. 3 is a diagram illustrating a phosphor portion in the light source device according to the first embodiment. The figure which shows the mechanism in which the excitation light and fluorescence light recur in Example 1. FIG. The figure which shows the fluorescent substance part in the light source device of Example 2 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a configuration of a light source device 1 that is Embodiment 1 of the present invention. The light source device 1 includes a light source unit 301 and a phosphor unit 302. In the light source unit 301, a plurality of sets of laser diodes (LDs) 303 and collimating lenses 304 provided in a one-to-one manner are arranged in an array. In this embodiment, the LD 303 emits blue laser light (hereinafter simply referred to as blue light) 305.

  The phosphor unit 302 includes a plurality of fluorescent portions 306 provided one-on-one with respect to a plurality of LDs 303, and a condensing lens 307 and a collimating lens 308 provided for each fluorescent portion 306. Has been. The plurality of condensing lenses 307 and the plurality of collimating lenses 308 are each formed in an array on an integrated optical member. The fluorescent part 306 is disposed between the condenser lens 307 and the collimator lens 308.

  The blue light 305 from the light source unit 301 is collected by the condenser lens 307 and enters the fluorescent unit 306. A part of the blue light 305 incident on the fluorescent part 306 is yellow, which is fluorescent light after being wavelength-converted by a phosphor (a wavelength converting element as a light characteristic converting element, which will be described later) in the fluorescent part 306. The light 309 is emitted from the fluorescent portion 306. Further, the non-converted light that has not been wavelength-converted by the phosphor among the blue light 305 incident on the fluorescent part 306 is emitted from the fluorescent part 306 as blue light. White light that is a combined light of the blue light 305 and the yellow light 309 emitted from the fluorescent unit 306 is collimated by the collimating lens 308 and emitted from the phosphor unit 302 (that is, the light source device 1). White light emitted from the light source device 1 enters an illumination optical system of a projector described later and is used as illumination light.

  FIG. 2 shows a detailed configuration of the fluorescent unit 306 shown in FIG. In the following description, the light source unit 301 side is referred to as a light source side, and the side from which light is emitted from the phosphor unit 302 is referred to as an emission side. The fluorescent unit 306 includes a reflective polarizing film (polarizing layer) 401, a quarter-wave film (retardation layer) 402, a dichroic film (dichroic layer) 403, and a phosphor 404, which are sequentially arranged from the light source side to the emission side. Has been. That is, in the light source device 1, the light source unit 301, the reflective polarizing film 401, the quarter wavelength film 402, the dichroic film 403, and the phosphor 404 are arranged in this order.

  Here, the phosphor 404 generates fluorescent light that is wavelength-converted light (characteristic-converted light) having a wavelength different from that of the excitation light that is incident light. In order to improve the recursive efficiency of the excitation light described later, The phosphor 404 is preferably a single crystal phosphor. When the excitation light passes through the single crystal phosphor, the polarization state is preserved without causing random disorder of the polarization state (polarization direction). Therefore, the polarization light in the polarization conversion element included in the illumination optical system of the projector described above is used. This is effective for improving the conversion efficiency. Both the excitation light and the wavelength conversion light (characteristic conversion light) include light having a wavelength in the visible light region (about 400 nm to 700 nm).

  Part of the blue light 305 that is excitation light that has entered the phosphor 404 through the condenser lens 307 is converted into fluorescent light having a spectrum in the green to red band, that is, the yellow light 309 described above. The yellow light 309 that is fluorescent light is emitted in all directions from the inside of the phosphor 404 as indicated by broken line arrows in the drawing. Further, as described above, the blue light (shown by a solid line in the figure) that is non-converted light that has not been converted into fluorescent light among the excitation light and is directed to the emission side is combined with the yellow light 309 that is directed to the emission side. The white light 405 is emitted from the collimating lens 308.

  FIG. 3 shows the behavior of light toward the light source in the fluorescent portion 306. The dichroic film 403 has a function of transmitting blue light and reflecting yellow light. The reflective polarizing film 401 transmits first polarized light (linearly polarized light) having a first polarization direction 501 and has a second polarization direction 505 different from (for example, orthogonal to) the first polarization direction 501. It has a function of reflecting the second polarized light (linearly polarized light). The quarter-wave film 402 converts the first polarized light into circularly polarized light by passing once, and further converts the circularly polarized light into second polarized light by passing this circularly polarized light once. It has the function to do. That is, the quarter wavelength film 402 converts the first polarized light into the second polarized light by passing twice. That is, the ¼ wavelength film 402 transmits the first polarized light emitted from the reflective polarizing film 401 from the polarizing film 401 side toward the phosphor 404 side, and then reenters the phosphor 404 and becomes 1 The light transmitted toward the / 4 wavelength film 402 is formed to be the second polarized light.

  Of the yellow light 309, the component (return light component) 502 directed to the light source side is reflected by the dichroic film 403 and proceeds to the emission side as a recursive light component 503, and is used as illumination light. Thereby, the utilization efficiency of fluorescent light can be improved.

  The LD 303 emits blue light 305 as linearly polarized light in the first polarization direction 501. Part of the blue light 305 that has entered the fluorescent portion 306 and passed through the quarter-wave film 402 and converted into circularly polarized light is the interface between the dichroic film 403 and the phosphor 404 or the phosphor 404 and the collimator lens 308. Causes Fresnel reflection at the interface with Thereby, part of the blue light 305 becomes return light components 504a and 504b toward the light source.

  The return light component 504 a from the interface between the dichroic film 403 and the phosphor 404 passes through the quarter wavelength film 402 again and returns to the reflective polarizing film 401. When the return light component 504 a that is circularly polarized light passes through the quarter wavelength film 402 again, the return light component 504 a is converted into the second polarized light, and is reflected by the reflective polarizing film 401.

  On the other hand, the return light component 504 b from the interface between the phosphor 404 and the collimator lens 308 passes again through the dichroic film 403 and the quarter wavelength film 402 and returns to the reflective polarizing film 401. Since the return light component 504 b that is circularly polarized light passes through the quarter wavelength film 402 again, the return light component 504 b is also converted into the second polarized light, and is reflected by the reflective polarizing film 401.

  The return light components 504a and 504b reflected by the reflective polarizing film 401 in this way become a retroreflective component 506 and travel to the emission side, pass through the quarter-wave film 402 and the dichroic film 403, and return to the phosphor 404. Used as excitation light or blue illumination light. Thereby, the recurrence efficiency of the excitation light can be improved, that is, the utilization efficiency of the excitation light from the light source unit 301 can be improved.

  The dichroic film 403 used for recurring fluorescent light need not be disposed immediately before the phosphor 404 as shown in FIG. 3, and may be closer to the light source than the quarter-wave film 402, It may be closer to the light source than the reflective polarizing film 401. That is, it may be between the light source unit 301 and the phosphor 404.

  According to this embodiment, in the light source device 1 using the blue light 305 from the light source unit 301 as the excitation light of the phosphor 404, the light utilization efficiency can be increased by reducing the return light component to the light source side.

  The focal length of the condensing lens 307 and the collimating lens 308 will be described. In this embodiment, an optical element having angular characteristics such as a reflective polarizing film or a dichroic film is used in order to increase the light utilization efficiency. For this reason, by selecting a long focal length for the condenser lens 307 and the collimating lens 308, the incident light flux to the polarizing film, the quarter wavelength film and the dichroic film becomes perpendicular to the film. Light utilization efficiency can be increased.

As an example of a preferable focal length f, when the thickness of the phosphor 404 is d,
0.5 <f / d
It is preferable to satisfy the following conditions. More preferably,
0.5 <f / d <100
It is better to satisfy the following conditions. However, the focal length f is not limited to the above range, and it is desirable that the focal length f be determined comprehensively in consideration of factors such as the phosphor 404, the brightness of the light source, and size restrictions.

  FIG. 4 shows the configuration of the fluorescent section 306 ′ in the light source device that is Embodiment 2 of the present invention. As described in Embodiment 1, in order to improve the recurrence efficiency of the excitation light, it is desirable to use a single crystal phosphor that preserves the polarization state of incident light as the phosphor 404. However, if a single crystal phosphor is used, the coherence of the laser light from the LD is stored without being disturbed, so it is necessary to take measures to prevent image quality deterioration such as speckle when projecting an image on the projector. In addition, when the fluorescent part 306 is inspected alone in the production process of the light source device, the laser light that is coherent light can be leaked to the outside, so there are facilities and measures for preventing such leakage of the coherent light. Necessary.

  Therefore, in this embodiment, a diffusion film (diffusion layer) 601 is disposed on the emission side of the phosphor 404 in the fluorescent section 306 described in Embodiment 1 (FIG. 3). Other configurations are the same as those in the first embodiment, and the same reference numerals as those in the first embodiment are given to the constituent elements common to the first embodiment.

  The diffusion film 601 diffuses the light (yellow light 309 and blue light 305) emitted from the phosphor 404. As a result, light with reduced coherence can be generated by the light source device alone.

  In the first and second embodiments, the case where the phosphor is used as the light characteristic conversion element has been described. However, other light characteristic conversion elements may be used. For example, a scattering plate may be used.

  FIG. 5 shows a configuration of an image projection apparatus (hereinafter referred to as a projector) using the light source device 1 of each of the above-described embodiments. In the projector, white light 102 (red light 102r, green light 102g, and blue light 102b indicated by dotted lines) emitted from the light source device 1 enters a projector optical system described below. First, red, green, and blue light 102r, 102g, and blue light 102b enter the polarization conversion element 103, where red, green, and blue illumination light (shown by dotted lines) 104r as linearly polarized light having a uniform polarization direction. , 104g, 104b.

  These illumination lights 104r, 104g, and 104b are separated by the dichroic mirror 105 into red illumination light 104r, blue illumination light 104b, and green illumination light 104g. The green illumination light 104g passes through the polarization separation element (hereinafter referred to as PBS) 108 and the phase compensation plate 112 and reaches the light modulation element 111g. The red and blue illumination lights 104 r and 104 b pass through the polarizing plate 106 and enter the color selective phase plate 107. The color selective phase plate 107 rotates the polarization direction of the blue illumination light 104b by 90 ° while maintaining the polarization direction of the red illumination light 104r as it is. The red illumination light 104r emitted from the color selective phase plate 107 passes through the PBS 109 and the phase compensation plate 112r and reaches the light modulation element 111r. The blue illumination light 104b emitted from the color selective phase plate 107 is reflected by the PBS 109, passes through the phase compensation plate 112b, and reaches the light modulation element 111b. Each light modulation element is constituted by a reflective liquid crystal panel or a digital micromirror device. A transmissive liquid crystal panel can also be used as the light modulation element.

  The light modulation elements 111g, 111r, and 111b modulate the incident green, red, and blue illumination lights 104g, 104r, and 104b to convert them into green, red, and blue image lights 115g, 115b, and 115r. The image lights 115g, 115b, and 115r are combined via the PBSs 108 and 109 and the combining prism 118, and projected onto a projection surface such as a screen by the projection lens 120. Thereby, a color image as a projection image is displayed.

  According to the present embodiment, a projector capable of projecting an image with stable color and brightness can be realized by using the light source device 1 with high light utilization efficiency.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

1 Light source device 303 LD
401 Reflective polarizing film 402 1/4 wavelength film 404 Phosphor

Claims (9)

From the light source side,
A polarizing layer that transmits first polarized light having a first polarization direction and reflects second polarized light having a second polarization direction different from the first polarization direction;
A retardation layer;
A light source device comprising: a light characteristic conversion element that generates characteristic conversion light having a characteristic different from that of incident light. The retardation layer is
Of the first polarized light emitted from the polarizing layer, it is transmitted from the polarizing layer side toward the optical characteristic polarizing element side, and further re-enters from the optical characteristic conversion element toward the retardation layer. The light source device according to claim 1, wherein the light source device is formed so that the transmitted light becomes the second polarized light having the second polarization direction.   3. The light source device according to claim 1, wherein both the incident light and the characteristic conversion light are light having a wavelength in a visible light region.   The said optical characteristic conversion element is a wavelength conversion element which produces | generates the wavelength conversion light as said characteristic conversion light in which a wavelength differs from the said incident light, The Claim 1 characterized by the above-mentioned. Light source device.   The light source device according to claim 4, wherein the wavelength conversion element is a phosphor.   The light source device according to claim 5, wherein the phosphor is a single crystal phosphor.   The dichroic layer which transmits the light from the light source and reflects the wavelength converted light is provided between the light source and the wavelength conversion element. The light source device according to 1.   The light source device according to claim 1, further comprising a diffusion layer that diffuses light emitted from the light characteristic conversion element. A light source device according to any one of claims 1 to 8,
A light modulation element for modulating light;
An image projection apparatus comprising: an optical system that guides light from the light source device to the light modulation element and projects an image using the light from the light modulation element.