JP2015179291A - Laser light source device and image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser light source device capable of sufficiently reducing speckle noise, and an image projection device.SOLUTION: The image projection device comprises at least one laser light source device, and uses light emitted from the laser light source device as projection light. The laser light source device comprises a plurality of laser light sources each emitting the same colour laser beam. Beams emitted from at least two laser light sources of the plurality of laser light sources have the same incident angle of an optical axis with respect to the incidence plane of a transparent material. The at least two laser light sources emit light of different wavelengths from each other.

Description

  The present invention relates to a laser light source apparatus including a plurality of laser light sources that emit laser light, and also relates to an image projection apparatus including the laser light source apparatus.

  Conventionally, as a laser light source device, a laser light source device in which laser beams emitted from a plurality of laser light sources are incident on an optical fiber or the like is known (for example, Patent Document 1). A technique is known in which light emitted from such a laser light source device is used as a light source for an exposure light source device or a projector. In such a technique, noise with the intensity of light called speckle noise is generated on the laser light irradiation surface and the retina of the observer.

  Therefore, in Patent Document 1, in order to reduce speckle noise, a laser light source device is proposed in which at least one of the plurality of laser light sources emits light having a wavelength different from that of the other laser light sources. . However, in the laser light source device according to Patent Document 1, there is a limit to the range of wavelengths that can be used, and therefore sufficient speckle noise reduction (also referred to as “despeckle effect” or “speckle contrast reduction”) can be obtained. There is a problem that it is not possible.

JP 2004-146793 A

  Therefore, in view of such circumstances, an object of the present invention is to provide a laser light source device and an image projection device that can sufficiently reduce speckle noise.

  A laser light source device according to the present invention includes a plurality of laser light sources that emit laser beams of the same color, and a light guide having an incident surface on which light emitted from the plurality of laser light sources is incident, The light emitted from at least two laser light sources among the plurality of laser light sources has the same incident angle of the optical axis with respect to the incident surface, and the at least two laser light sources emit light having different wavelengths.

  The laser light source device according to the present invention includes a plurality of laser light sources that emit laser light of the same color and light emitted from the plurality of laser light sources, and the light is incident on an incident surface of the light guide. And at least two laser light sources out of the plurality of laser light sources, the incident angles of the optical axes with respect to the incident surface are equal, and the at least two laser light sources are , Emit light of different wavelengths.

  According to such a configuration, at least two laser light sources that emit light having the same incident angle of the optical axis with respect to the incident surface are provided. Of these laser light sources, at least two laser light sources emit light of different wavelengths. As a result, a sufficient amount of light can be incident on the light guide, and the generation of speckle noise can be suppressed.

  An image projection apparatus according to the present invention includes at least one of the laser light source devices, and uses light emitted from the laser light source device as projection light.

  As described above, the present invention has an excellent effect that a sufficient reduction in speckle noise can be obtained.

FIG. 1 is a schematic configuration diagram of an image projection apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of the laser light source device according to the embodiment. FIG. 3 is a diagram illustrating an incident pattern of light incident on the optical system according to the embodiment. FIG. 4 is a diagram for explaining an incident angle of light on an incident surface of the light guide according to the embodiment. FIG. 5 is a diagram illustrating “different wavelengths” according to the embodiment. FIG. 6 is a diagram illustrating “different wavelengths” according to the embodiment. FIG. 7 is a diagram for explaining an effect when light of the same wavelength is incident on the incident surface of the light guide at different angles, and is a diagram illustrating an incident pattern of light incident on the optical system. FIG. 8 is a diagram for explaining an effect when light of different wavelengths is incident on the incident surface of the light guide, and is a diagram illustrating an incident pattern of light incident on the optical system. FIG. 9 is a diagram for explaining an incident pattern of light incident on an optical system according to another embodiment of the present invention. FIG. 10 is a diagram illustrating an incident pattern of light incident on an optical system according to still another embodiment of the present invention.

  Hereinafter, an embodiment of a laser light source device and an image projection device according to the present invention will be described with reference to FIGS.

  As shown in FIG. 1, the image projection apparatus 1 according to the present embodiment includes a plurality (three in the present embodiment) of laser light source devices 2 (2R, 2G, and 2B) that emit light of different colors. And a spatial modulation element 3 that converts the light emitted from each laser light source device 2 into an optical image. The image projection apparatus 1 also combines a color synthesis optical member 4 that synthesizes the light images emitted from the spatial modulation elements 3, and light that projects the light image emitted from the color synthesis optical member 4 on the screen 100. And an image projection mechanism 5.

  The laser light source device 2 includes a first laser light source device 2R that emits laser light of a first color (for example, red) and a second laser light source that emits laser light of a second color (for example, green). An apparatus 2G and a third laser light source apparatus 2B that emits laser light of a third color (for example, blue) are provided. The spatial modulation element 3 is composed of, for example, a digital micromirror device or a liquid crystal display device, the color composition optical member 4 is composed of, for example, a color composition prism such as a dichroic prism, and the optical image projection mechanism 5 is composed of, for example, And a projection lens.

  As shown in FIG. 2, the laser light source device 2 according to this embodiment includes a plurality of laser light sources 21 that emit laser light, an optical system 22 that receives light emitted from the plurality of laser light sources 21, and an optical system. And a light guide 23 having an incident surface 23a on which light emitted from the system 22 is incident. In the laser light source device 2, the light emitted from the light guide 23 is incident on the spatial modulation element 3.

  The laser light source 21 includes a semiconductor laser 211 that emits laser light and a collimator lens 212 that collimates the laser light emitted from the semiconductor laser 211. The plurality of laser light sources 21 are arranged so that the optical axes of the emitted light are parallel to each other at least when entering the optical system 22.

  In addition, the plurality of laser light sources 21 are arranged so that the optical axes of the emitted light are at different positions on the incident surface 22 a of the optical system 22. Preferably, the plurality of laser light sources 21 (particularly, laser light sources 21 that output light of the same wavelength) are arranged so that the emitted light does not overlap with each other on the incident surface 22 a of the optical system 22.

  The plurality of laser light sources 21 emit light having a plurality of wavelengths. In the present embodiment, nine laser light sources 21 are provided (only four are shown in FIG. 2). For example, in the second laser light source device 2G, a laser light source 21 that emits light of a first wavelength (for example, a wavelength of 530 nm) and a laser that emits light of a second wavelength (for example, a wavelength of 532 nm). Three light sources 21 and three laser light sources 21 that emit light of a third wavelength (for example, a wavelength of 534 nm) are provided.

  In this embodiment, the optical system 22 is a condensing lens that condenses the light emitted from the plurality of laser light sources 21 toward the center of the incident surface 23 a of the light guide 23. In other words, the optical system 22 changes (refracts) the optical axis of the light emitted from each laser light source 21 toward the center of the incident surface 23 a of the light guide 23.

  The light guide 23 is formed in a long shape, and a planar incident surface 23a is disposed at one end and a planar exit surface 23b is disposed at the other end. The light guide 23 is configured to propagate the light along the longitudinal direction while maintaining the angle at which the light incident on the incident surface 23a travels by totally reflecting the light on its side surface. Yes.

  In the present embodiment, the light guide 23 is an optical fiber including a core that is a core, a cladding that is disposed outside the core and has a lower refractive index than the core, and a coating that covers the cladding (only the core is illustrated). Shown). That is, the incident surface 23a is constituted by a surface on one end side of the core. The light guide 23 is not limited to an optical fiber, and may be, for example, a rod integrator.

  Here, an arrangement angle of each laser light source 21 (an incident position of light with respect to the optical system 22) and an incident angle and an incident position of light on the incident surface 23a of the light guide 23 due to the action of the optical system 22 will be described.

  As shown in FIG. 3, light L11, L12, L13 having the same first wavelength is emitted from three laser light sources 21, 21, 21. Further, light L21, L22, and L23 having the same second wavelength is emitted from the three laser light sources 21, 21, and 21. Further, light L31, L32, and L33 having the same third wavelength are emitted from the three laser light sources 21, 21, and 21. 3 shows the incident positions of the lights L11 to L13, L21 to L23, and L31 to L33 with respect to the incident surface 22a of the optical system 22.

  By the way, in this embodiment, the light from the laser light source 21 is condensed toward the center of the incident surface 23 a of the light guide 23 by the optical system 22. Therefore, when the optical axis of the light emitted from the laser light source 21 is located at a different distance from the center on the incident surface 22a of the optical system 22, the incident angle of the optical axis with respect to the incident surface 23a of the light guide 23 is Will be different.

  For example, in L11, L12, and L13, which are light having the same first wavelength, the optical axes A11, A12, and A13 are located at different distances from the center on the incident surface 22a of the optical system 22. Therefore, in L11, L12, and L13, which are light having the same first wavelength, the incident angles θ1, θ2, and θ3 of the optical axes A11, A12, and A13 with respect to the incident surface 23a of the light guide 23 are shown in FIG. Are different.

  Returning to FIG. 3, the optical axes A21, A22, and A23 are located at different distances from the center on the incident surface 22a of the optical system 22 even in L21, L22, and L23, which are light having the same second wavelength. Therefore, also in the light L21, L22, and L23 having the same second wavelength, the incident angles θ1, θ2, and θ3 of the optical axes A21, A22, and A23 with respect to the incident surface 23a of the light guide 23 are different.

  Similarly, in L31, L32, and L33, which are light having the same third wavelength, the optical axes A31, A32, and A33 are located at different distances from the center on the incident surface 22a of the optical system 22. Accordingly, even in the light beams L31, L32, and L33 having the same third wavelength, the incident angles θ1, θ2, and θ3 of the optical axes A31, L32, and A33 with respect to the incident surface 23a of the light guide 23 are different.

  When the optical axis of the light emitted from the laser light source 21 is located at the same distance from the center (the position indicated by the broken line in FIG. 3) on the incident surface 22a of the optical system 22, the incident surface 23a of the light guide 23 is used. The incident angle of the optical axis with respect to is the same position. Therefore, in the light of the same wavelength, the incident angles of the optical axis with respect to the incident surface 23a of the light guide 23 are all different, and in the light with the same incident angle of the optical axis with respect to the incident surface 23a of the light guide 23. The wavelengths are all different.

  Here, “light of different wavelengths” and “light of equal wavelengths” in the present embodiment will be described with reference to FIGS.

  As shown in FIG. 5, the spectrum (wavelength-spectrum intensity graph) is calculated so that the area becomes 1 for the light emitted from each laser light source 21. Note that the spectrum shown in FIG. 5 is a spectrum of the laser semiconductor 211 composed of a plurality of (for example, 24) light emitting portions (emitters), and thus has an uneven shape.

  As shown in FIG. 6, it is determined whether the two lights have the same wavelength or different wavelengths by calculating the area of the overlapping portion (shaded portion in FIG. 6) of the spectrum of the two lights. Specifically, different wavelengths are used when the overlapping area is 0.24 or less. Preferably, the wavelengths are different when the area of the overlapping portion is 0.07 or less. More preferably, the wavelengths are different when the area of the overlapping portion is 0.07 or less and the peak wavelength is more than the average value of the full width at half maximum of the spectrum. In addition, when the area of an overlapping part is larger than 0.24, it is set as an equal wavelength.

  Further, in the present embodiment, “incident angles are different” when the difference in the incident angle of the optical axis with respect to the incident surface 23a of the light guide 23 is 2 ° or more in the two lights. Preferably, in the two lights, when the difference in the incident angle of the optical axis with respect to the incident surface 23a of the light guide 23 is 5 ° or more, “the incident angles are different”. More preferably, in the two lights, when the difference in the incident angle of the optical axis with respect to the incident surface 23a of the light guide 23 is 8 ° or more, “the incident angles are different”. In the two lights, when the difference in the incident angle of the optical axis with respect to the incident surface 23a of the light guide 23 is smaller than 2 °, “the incident angles are equal”.

  Next, the effects of the laser light source device 2 according to the present embodiment will be verified with reference to FIGS. 7 and 8 show the incident position of each light with respect to the incident surface 22a of the optical system 22, as shown in FIG.

  In order to verify, the light emitted from the laser light source device 2 is incident on the rod integrator, the end surface image of the rod integrator is projected on the screen 100 by about 100 times, and the screen 100 is photographed with a CCD camera. The speckle contrast was measured from the image projected on the screen 100. The speckle contrast is obtained by dividing the standard deviation of the light intensity at each pixel of the CCD by the average value of the light intensity at each pixel. The larger the speckle contrast is, the higher the intensity of the light intensity (speckle noise). .

  As shown in FIG. 7, the case where the same two lights L41 and L42 having a wavelength of 530 nm exist is verified. When the optical axes A41 and A42 of the lights L41 and L42 having the same wavelength are located at the same distance from the center on the incident surface 22a of the optical system 22, that is, the optical axis A41 with respect to the incident surface 23a of the light guide 23. , A42 have the same incident angle, the speckle contrast is 9.5%.

  On the other hand, when the optical axes A41 and A42 of the lights L41 and L42 having the same wavelength are located at different distances from the center on the incident surface 22a of the optical system 22, that is, the incident surface 23a of the light guide 23. When the incident angles of the optical axes A41 and A42 are different from each other, the speckle contrast is 8.2%. Thereby, in the light of the same wavelength, since the incident angle of the optical axis with respect to the incident surface 23a of the light guide 23 is different, speckle noise can be reduced.

  Further, as shown in FIG. 8, the case where the same two lights L51 and L52 having a wavelength of 530 nm and one light L53 having a wavelength of 534 nm are present is verified. When the optical axes A51 to 53 of the lights L51 to 53 are located at different distances from the center on the incident surface 22a of the optical system 22, that is, the optical axes A51 to A53 of the light guide 23 with respect to the incident surface 23a. When all the incident angles are different, the speckle contrast is 7.5%.

  On the other hand, when the optical axes A51 and 53 of the light beams L51 and L53 having different wavelengths are located at the same distance from the center on the incident surface 22a of the optical system 22, that is, on the incident surface 23a of the light guide 23. On the other hand, when the incident angles of the optical axes A51 and A53 of the light beams L51 and L53 having different wavelengths are equal, the speckle contrast is 7.7%. Thereby, in the light with the same incident angle of the optical axis with respect to the incident surface 23a of the light guide 23, generation | occurrence | production of a speckle noise can be suppressed because a wavelength differs.

  As described above, according to the image projection device 1 and the laser light source device 2 according to the present embodiment, the light emitted from the plurality of laser light sources 21 is incident on the optical system 22, and the light emitted from the optical system 22 is The light enters the incident surface 23 a of the light guide 23. And in the light radiate | emitted from the several laser light source 21, the incident angle of the optical axis with respect to the entrance plane 23a of the light guide 23 differs. Thereby, speckle noise can be reduced.

  Moreover, according to the image projector 1 and the laser light source device 2 which concern on this embodiment, the laser light source 21 which radiate | emits the light of the same wavelength is provided 3 each. And in light L11-L13 (L21-L23, L31-L33) radiate | emitted from those laser light sources 21, the optical axes A11-A13 (A21-A23, A31-A33) with respect to the entrance plane 23a of the light guide 23 are shown. Are different from each other. Thereby, speckle noise can be more effectively reduced.

  Further, according to the image projection device 1 and the laser light source device 2 according to the present embodiment, the optical axes L11, L21, L31 (L12, L22, L32) (L13, L23, L33) with respect to the incident surface 23a of the light guide 23 are used. Three laser light sources 21 that emit light having the same incident angle θ1 (θ2) (θ3) are provided. These laser light sources 21 emit light having different wavelengths. As a result, a sufficient amount of light can be incident on the light guide 23 and the occurrence of speckle noise can be suppressed.

  In addition, this invention is not limited to the structure of above-described embodiment, Moreover, it is not limited to an above-described effect. In addition, the present invention can be variously modified without departing from the gist of the present invention. For example, it is needless to say that configurations, methods, and the like according to various modifications described below may be arbitrarily selected and employed in the configurations, methods, and the like according to the above-described embodiments.

  The image projection apparatus 1 according to the above embodiment is configured to include three laser light source devices 2R, 2G, and 2B. However, the image projector 1 according to the present invention is not limited to such a configuration. For example, the image projection apparatus 1 according to the present invention may have a configuration including one laser light source device 2, a configuration including two laser light source devices 2, and a configuration including four or more laser light source devices 2. .

  In the laser light source device 2 according to the above-described embodiment, the plurality of laser light sources 21 emit light having a plurality of wavelengths. However, the laser light source device 2 according to the present invention is not limited to such a configuration. For example, in the laser light source device 2 according to the present invention, the plurality of laser light sources 21 may emit light L61 to 66 having the same wavelength as shown in FIG.

  9 shows the incident positions of the lights L61 to L66 with respect to the incident surface 22a of the optical system 22, as shown in FIG. FIG. 9 shows that six lights L61 to L66 having the same wavelength are incident on the incident surface 22a of the optical system 22.

  In such a configuration, not only light having different incident angles of the optical axes A61 (A62, A63) and A64 (A65, A66) with respect to the incident surface 23a of the light guide 23, but also an optical axis with respect to the incident surface 23a of the light guide 23 The structure that the light with the same incident angle of A61-A63 (A64-A66) also exists may be sufficient. Of course, a configuration in which only light having different incident angles of the optical axis with respect to the incident surface 23a of the light guide 23 may exist.

  Further, the laser light source device 2 according to the above-described embodiment has a configuration in which the incident angle of the optical axis with respect to the incident surface 23a of the light guide 23 is different for light having the same wavelength. However, the laser light source device 2 according to the present invention is not limited to such a configuration. For example, as shown in FIG. 10, the laser light source device 2 according to the present invention guides a part of the light L72, L73 (L75, L76) among the light L72, L73, L75, L76 having the same wavelength. The structure that the incident angle of the optical axis with respect to the incident surface 23a of the body 23 is equal may be sufficient.

  10 shows the incident positions of the lights L71 to L76 with respect to the incident surface 22a of the optical system 22, as shown in FIG. In FIG. 10, the two lights L71 and L74 having the first wavelength and the four lights L72, L73, L75, and L76 having the second wavelength are incident on the incident surface 22a of the optical system 22. Show.

  In addition, the laser light source device 2 according to the above-described embodiment has a configuration in which light having the same incident angle of the optical axis with respect to the incident surface 23a of the light guide 23 is light having different wavelengths. However, the laser light source device 2 according to the present invention is not limited to such a configuration. For example, as shown in FIG. 10, the laser light source device 2 according to the present invention includes some of the lights L71 and L72 (out of the lights L71 to L73 having the same incident angle of the optical axis with respect to the incident surface 23a of the light guide 23. L73) may be configured such that the wavelengths are different.

  In addition, the laser light source device 2 according to the embodiment is configured to be used in the image projection device 1. However, the laser light source device 2 according to the present invention is not limited to such a configuration. For example, the laser light source apparatus 2 according to the present invention may be configured to be used in an exposure apparatus that performs exposure using laser light.

  DESCRIPTION OF SYMBOLS 1 ... Image projector, 2, 2R, 2G, 2B ... Laser light source device, 3 ... Spatial modulation element, 4 ... Color synthetic | combination optical member, 5 ... Optical image projection mechanism, 21 ... Laser light source, 22 ... Optical system, 22a ... Incident surface, 23 ... light guide, 23a ... incident surface, 23b ... output surface, 100 ... screen, 211 ... semiconductor laser, 212 ... collimating lens

Claims (3)

A plurality of laser light sources that emit laser light of the same color;
A light guide having an incident surface on which light emitted from the plurality of laser light sources is incident,
In light emitted from at least two of the plurality of laser light sources, the incident angle of the optical axis with respect to the incident surface is equal,
The at least two laser light sources are laser light source devices that emit light of different wavelengths. A plurality of laser light sources that emit laser light of the same color;
An optical system that receives light emitted from the plurality of laser light sources and emits the light toward an incident surface of the light guide; and
In light emitted from at least two of the plurality of laser light sources, the incident angle of the optical axis with respect to the incident surface is equal,
The at least two laser light sources are laser light source devices that emit light of different wavelengths. An image projection apparatus comprising at least one laser light source device according to claim 1 or 2, wherein light emitted from the laser light source device is used as projection light.

Images