JP2009181753A - Planar light emitting device, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar light-emitting device capable of improving uniformity of luminance. <P>SOLUTION: The planar light-emitting device 100 includes semiconductor laser light sources 1a-1c of multi-stripe structure to emit a plurality of laser beams, a light guide plate 9 which introduces the laser beams from an incident face and surface-emits from an outgoing face, first beam shaping lenses 2a-2c which convert the laser beams emitted from the semiconductor laser light sources 1a-1c in nearly parallel light in slow-axis direction, second beam shaping lenses 3a-3c which convert the laser beams emitted from the semiconductor laser light sources 1a-1c in nearly parallel light in fast-axis direction, and an intensity distribution conversion part 6 which converts intensity distribution of the laser beams emitted from the semiconductor laser light sources 1a-1c into nearly uniform intensity distribution in the longitudinal direction of the incident face 9a of the light guide plate 9. The fast-axis direction of the laser beams emitted from the semiconductor laser light sources 1a-1c which enter the incident face 9a of the light guide plate 9 coincides with the longitudinal direction of the incident face 9a of the light guide plate 9. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface light emitting device and an image display device.

  In recent years, with the widespread use of mobile phones and information devices, a thin and high-quality screen display device has been demanded. In order to realize such a screen display device, a thin liquid crystal display element having a good color reproducibility using a laser as a light source has been proposed (Patent Documents 1 and 2).

  The color display element described in Patent Document 1 includes a backlight for illuminating a liquid crystal panel, a light guide plate, a plurality of laser light sources corresponding to the three primary colors arranged on an arbitrary surface of the light guide plate, and a light guide. By comprising irregularly reflecting particles disposed inside the light plate and reflecting plates disposed on the side and bottom surfaces of the light guide plate, color display can be performed with light having high color purity.

The planar light source described in Patent Document 2 includes a reflecting member that reflects light emitted from a laser light source substantially parallel to a predetermined direction, and a polarizing member that reflects reflected light reflected by the reflecting member in a substantially right angle direction. By configuring, a collimated planar light source can be obtained with a simple configuration using a single laser beam.
Japanese Patent Application Laid-Open No. 11-237631 JP 2002-169480 A

  However, in the color display element described in Patent Document 1, there is a problem that luminance unevenness is likely to occur because a laser that is a substantially point light source is disposed on the side surface of the light guide plate. In addition, the planar light source described in Patent Document 2 uses a reflective volume hologram as a reflecting member, and thus has a problem that it is sensitive to manufacturing errors and it is difficult to increase luminance uniformity.

  The present invention has been made in view of such points, and an object thereof is to provide a surface light emitting device and an image display device capable of improving the uniformity of luminance.

  The surface emitting device of the present invention includes a multi-stripe semiconductor laser light source that emits a plurality of laser beams, a light guide plate that guides laser light from an incident surface and emits light from the emitting surface, and emits light from the semiconductor laser light source. A first optical system that converts the laser beam into substantially parallel light in the slow axis direction; a second optical system that converts the laser light emitted from the semiconductor laser light source into substantially parallel light in the fast axis direction; An intensity distribution conversion unit that converts the intensity distribution of the laser light emitted from the semiconductor laser light source into a substantially uniform intensity distribution in the longitudinal direction of the incident surface of the light guide plate, and on the incident surface of the light guide plate A configuration is adopted in which the fast axis direction of the laser beam converted by the incident intensity conversion unit coincides with the longitudinal direction of the incident surface of the light guide plate.

  The image display device of the present invention employs a configuration having the surface light-emitting device having the above-described configuration and a display panel disposed on the exit surface side of the light guide plate.

  According to the present invention, the uniformity of luminance can be improved.

(Embodiment 1)
<Configuration of surface light emitting device>
FIG. 1 is a cross-sectional view showing a schematic configuration of a surface light emitting device according to Embodiment 1 of the present invention. 2 is a cross-sectional view in a direction perpendicular to FIG. 1, showing a schematic configuration of the main part of FIG.

  1 and 2 includes a laser light source 1, a first beam shaping lens 2, a second beam shaping lens 3, a color synthesis prism 4, a bending mirror 5, a first aspheric lens 6, and a second non-spherical lens. It has a spherical lens 7, a cylindrical lens 8, and a light guide plate 9. Here, as shown in FIGS. 1 and 2, the transverse direction and the longitudinal direction of the incident end face 9a of the light guide plate 9 are respectively defined as the X axis and the Y axis, and the direction orthogonal to the X axis and the Y axis is Z. Axis. 1 is a cross-sectional view taken along the XZ plane of the surface light emitting device 100, and FIG. 2 is a cross-sectional view taken along the YZ plane from the first aspherical lens 6 to the light guide plate 9 in the surface light emitting device 100 of FIG. is there.

  In FIG. 1, a laser light source 1 includes three semiconductor laser light sources (hereinafter simply referred to as “semiconductor lasers”) 1a, 1b, and 1c that emit laser light having wavelengths corresponding to the three primary colors (red, green, and blue). It is configured. Each of the semiconductor lasers 1a, 1b, and 1c has a multi-stripe structure and is composed of two semiconductor lasers. For example, the semiconductor laser 1a is composed of semiconductor lasers 1a-1 and 1a-2 that emit red laser light having a wavelength of 635 nm, and the semiconductor laser 1b is a semiconductor laser 1b-1 that emits green laser light having a wavelength of 532 nm. The semiconductor laser 1c is composed of semiconductor lasers 1c-1 and 1c-2 that emit blue laser light having a wavelength of 450 nm. As will be described later, the laser light emitted from the semiconductor lasers 1a to 1c has a direction in which the beam divergence angle is large (fast axis direction) and a direction in which the beam divergence angle is small (slow axis direction). In the present embodiment, in order to increase the uniformity of luminance, the semiconductor laser is arranged so that the fast axis direction of the laser light incident on the incident end surface 9a of the light guide plate 9 and the longitudinal direction of the incident end surface 9a of the light guide plate 9 coincide. 1a to 1c are arranged. This principle will be described in detail later.

  The first beam shaping lens 2 is a beam shaping lens having power only in the X-axis direction. That is, the first beam shaping lens 2 converts the laser light emitted from the laser light source 1 into substantially parallel light in the X-axis direction and shapes it into a predetermined beam shape. Laser beam shaping is performed, for example, by controlling the beam diameter and divergence angle (curvature radius of curvature) of the laser beam to desired values, respectively. In the present embodiment, first beam shaping lenses 2a, 2b, and 2c are provided corresponding to the semiconductor lasers 1a, 1b, and 1c, respectively. That is, each of the first beam shaping lenses 2a to 2c controls the beam diameter and divergence angle of the laser light from the corresponding semiconductor lasers 1a to 1c to desired values, and shapes the laser light into a predetermined beam shape. . Each of the first beam shaping lenses 2a, 2b, and 2c has an array shape formed of a plurality of lens elements corresponding to a plurality of semiconductor lasers constituting a multi-stripe structure semiconductor laser. Specifically, since each of the semiconductor lasers 1a to 1c is composed of two semiconductor lasers as described above, the first beam shaping lens 2a is composed of lens elements 2a-1 and 2a-2. The first beam shaping lens 2b has an array shape formed of lens elements 2b-1 and 2b-2, and the first beam shaping lens 2c has a lens element 2c-1. 2c-2. Each of the first beam shaping lenses 2a to 2c individually converts the laser light for each semiconductor laser into substantially parallel light in the X-axis direction and shapes the laser light into a predetermined beam shape. The first beam shaping lenses 2a to 2c will be described in detail later.

  The second beam shaping lens 3 is a beam shaping lens having power only in the Y-axis direction. That is, the second beam shaping lens 3 converts the laser light emitted from the laser light source 1 into substantially parallel light in the Y-axis direction and shapes it into a predetermined beam shape. In the present embodiment, second beam shaping lenses 3a, 3b, and 3c are provided corresponding to the semiconductor lasers 1a, 1b, and 1c, respectively. For example, in the example of FIG. 1, each of the second beam shaping lenses 3a to 3c converts the laser beam from the corresponding semiconductor laser 1a to 1c into a parallel beam having a beam diameter A (FIG. 3 to be described later). (See (A)). The laser beams (parallel light) 10a, 10b, and 10c emitted from the respective semiconductor lasers 1a to 1c and beam-shaped by the corresponding second beam-shaping lenses 3a to 3c are incident on the color combining prism 4. The second beam shaping lenses 3a to 3c will be described in detail later.

  The color synthesis prism 4 synthesizes laser beams 10a to 10c emitted from the laser light source 1 (semiconductor lasers 1a to 1c) and beam-formed by the first beam shaping lenses 2a to 2c and the second beam shaping lenses 3a to 3c. Then, one laser beam 10 is emitted. The optical path of the synthesized laser beam 10 is changed by the bending mirror 5 (bent by 90 ° in the example of FIG. 1), and in order, the first aspheric lens 6, the second aspheric lens 7, and the cylindrical lens. 8 and the light guide plate 9.

  The first aspherical lens 6 functions as an intensity distribution conversion element that constitutes an intensity distribution conversion unit, and converts the intensity distribution of laser light (here, synthesized laser light 10) emitted from the laser light source 1 into a light guide plate. 9 is converted into a substantially uniform intensity distribution in the longitudinal direction of the incident end face 9a.

  Specifically, for example, the first aspheric lens 6 is an aspheric lens having power only in the Y-axis direction (see FIG. 2). That is, the first aspherical lens 6 converts the intensity distribution in the Y-axis direction of a parallel beam with a beam diameter A having a Gaussian intensity distribution into a substantially uniform intensity distribution and is incident on the second aspherical lens 7. The beam width is converted to a width substantially equal to the longitudinal width B of the incident end face 9a of the light guide plate 9. FIG. 3A is a diagram illustrating an example of the intensity distribution in the Y-axis direction of the laser light 10 in the vicinity of the incident surface of the first aspheric lens 6. FIG. 3B is a diagram illustrating an example of an intensity distribution in the Y-axis direction of the laser light 10 at a position incident on the second aspheric lens 7. As shown in FIGS. 3A and 3B, the first aspherical lens 6 changes the intensity distribution in the Y-axis direction of the laser light 10 from a Gaussian distribution with a beam diameter A to a uniform distribution with a width B. Convert.

  In the present embodiment, the first aspherical lens 6 uses a single aspherical lens as the intensity distribution conversion element constituting the intensity distribution conversion unit, but the present invention is not limited to this. For example, the first aspheric lens 6 may use an intensity distribution conversion element including an aspheric lens as a constituent element as the intensity distribution conversion element constituting the intensity distribution conversion unit.

  In the present embodiment, the laser beams 10a to 10c emitted from the respective semiconductor lasers 1a to 1c and beam-shaped by the corresponding first beam shaping lenses 2a to 2c and the second beam shaping lenses 3a to 3c are combined. Although it is combined into one laser beam 10 by the prism 4, at least a part of the laser beams 10a to 10c is not combined into one laser beam and is incident on the corresponding intensity distribution conversion element independently. May be.

  Similar to the first aspherical lens 6, the second aspherical lens 7 is an aspherical lens having power only in the Y-axis direction (see FIG. 2). The second aspheric lens 7 is a lens for making the laser light 10 incident on the light guide plate 9 substantially parallel light in the longitudinal direction of the incident end surface 9 a of the light guide plate 9. That is, the second aspherical lens 7 has a function of converting the laser light 10 made divergent light by the first aspherical lens 6 into parallel light again.

  On the other hand, the cylindrical lens 8 is a lens having power only in the X-axis direction (see FIG. 1). The cylindrical lens 8 is a lens for changing the divergence angle of the incident end surface 9a of the light guide plate 9 in the short direction. That is, the cylindrical lens 8 has a function of converting the X-axis direction of the laser light 10 incident on the light guide plate 9 into convergent light or divergent light.

  As described above, by providing an optical system in which the first aspherical lens 6, the second aspherical lens 7, and the cylindrical lens 8 are combined, the laser light 10 incident on the incident end surface 9 a of the light guide plate 9 is transmitted in the Y-axis direction. , The X-axis direction becomes convergent light or divergent light, and the Y-axis direction becomes substantially parallel light. Therefore, by optimizing this optical system, the laser light 10 emitted from the laser light source 1 has a substantially uniform distribution in the Y-axis direction, and the longitudinal direction and the short direction of the incident end surface 9a of the light guide plate 9. It can be efficiently guided to the incident end face 9a of the light guide plate 9 according to each width.

  The light guide plate 9 guides the laser beam 10 from the incident end surface 9a and emits the laser beam from the front surface 9b which is the exit surface to emit light in a planar shape. Here, as shown in FIG. 2, the longitudinal width of the incident end face 9 a of the light guide plate 9 is B. The light guide plate 9 is made of, for example, PMMA (acrylic resin), PC (polycarbonate), COP (cycloolefin polymer), or the like.

  The light guide plate 9 has, for example, a light diffusion layer disposed on the front surface 9b and a reflective sheet disposed on the back surface 9c. The light diffusion layer is formed from a light-transmitting resin containing a light diffusion material. As the light diffusion layer, for example, a polyethylene terephthalate provided with fine irregularities, or a white ink for irregular reflection printed on the front surface 9b is used. At this time, the diffusion degree of the light diffusion layer can be changed by adjusting the size of the fine unevenness or adjusting the size of each dot by the white ink. Moreover, as a reflection sheet, a metal film may be used and a metal may be vapor-deposited on the back surface 9c.

  Here, the distribution of the diffusion degree of the front surface 9b of the light guide plate 9 is formed so that the luminance of the laser light 10 emitted from the front surface 9b of the light guide plate 9 is uniform. Specifically, the light diffusion layer formed on the front surface 9b of the light guide plate 9 diffuses in accordance with the distance in the Z axis direction from the incident end surface 9a of the light guide plate 9 in order to make the luminance in the Z axis direction uniform. The configuration is changed. For example, here, the brightness in the Z-axis direction is made uniform by increasing the diffusion degree as the distance from the incident end face 9a of the light guide plate 9 increases.

  The laser light 10 incident on the light guide plate 9 is diffused by the light diffusion layer disposed on the front surface 9b of the light guide plate 9 while propagating through the light guide plate 9 while repeating total reflection. For this reason, a component of the laser beam that is incident on the front surface 9 b of the light guide plate 9 at an angle smaller than the critical angle appears in the diffused laser beam 10. This laser light component is uniformly emitted from the front surface 9 b of the light guide plate 9. Thereby, the light guide plate 9 emits light in a planar shape.

  In the present embodiment, the diffusion sheet is disposed on the front surface 9b of the light guide plate 9, but the present invention is not limited to this. For example, the diffusion sheet may be disposed on the back surface 9 c of the light guide plate 9. However, in this case, the light diffusion layer is disposed on the front surface 9b side with respect to the reflection sheet.

  In the present embodiment, as described above, in order to increase the uniformity of brightness, the fast axis direction of the laser light incident on the incident end surface 9a of the light guide plate 9 and the longitudinal direction of the incident end surface 9a of the light guide plate 9 match. The semiconductor lasers 1a to 1c are arranged as described above. This principle is as follows.

  Here, first, the structure of the semiconductor lasers 1a to 1c will be described. FIG. 4 is a schematic diagram showing a general structure of a semiconductor laser having a multi-stripe structure. In the present embodiment, semiconductor lasers having a general structure shown in FIG. 4 are used as the semiconductor lasers 1a to 1c, respectively.

  The semiconductor laser shown in FIG. 4 includes two electrodes 41, stripes 42, oxide films 43, P-type cladding layers 44, active layers 45, N-type cladding layers 46, substrates 47, electrodes 48, and laser emission surfaces 49 each. Have.

  As shown in FIG. 4, the semiconductor laser has a structure in which an active layer 45 having a small band gap is sandwiched between a P-type cladding layer 44 and an N-type cladding layer 46 having a large band gap. In this structure, when a forward voltage is applied from the electrodes 41, 48, holes are injected from the P-type cladding layer 44 and electrons are injected from the N-type cladding layer 46 to the active layer 45, respectively. An inversion distribution is formed inside. As a result, laser light is extracted from the laser emission surface 49 in the Z-axis direction of FIG.

  At this time, in the Y-axis direction of FIG. 4 (direction perpendicular to the width direction of the stripe 42), light is confined in the active layer 45 due to the difference in refractive index between the active layer 45 and the clad layers 44 and 46. . For this reason, the transverse mode in the Y-axis direction is determined by the width of the active layer 45 in the Y-axis direction. Usually, the width of the active layer 45 in the Y-axis direction is set to 1 to 2 μm, and the laser light is single mode in the Y-axis direction. In general, the Y-axis direction shown in FIG. 4 has a large divergence angle of laser light (beam), and is called “fast axis” as described above.

  On the other hand, in the X-axis direction in FIG. 4 (a direction parallel to the width direction of the stripe 42), an inversion distribution occurs only in the region of the stripe 42. Therefore, the laser beam in the X-axis direction can be adjusted by adjusting the width C of the stripe 42. Control the mode. For example, when the transverse mode is changed to the single mode (single mode oscillation), the width of the stripe 42 is set to several μm. When the transverse mode is set to the multimode (multimode oscillation), the width of the stripe 42 is set to several tens to several thousand microns. In general, the X-axis direction shown in FIG. 4 has a small divergence angle of laser light (beam) and is called “slow axis” as described above.

  In the present embodiment, in order to obtain a large laser output in the X-axis direction, the stripe 42 is widened to cause multimode oscillation. That is, in the present embodiment, the laser light emitted from the semiconductor lasers 1a to 1c is single-mode oscillation in the Y-axis (fast axis) direction and multi-mode oscillation in the X-axis (slow axis) direction. In general, a plurality of semiconductor lasers constituting a semiconductor laser having a multi-stripe structure are arranged in the slow axis direction. Therefore, as shown in FIG. 4, the laser emission surfaces 49 of the two semiconductor lasers constituting each of the semiconductor lasers 1a to 1c are arranged in the X-axis direction.

  Further, in the present embodiment, the Y-axis direction of FIG. 4 and the Y-axis direction of FIG. 2 are matched, that is, the fast axis direction of the laser beam 10 emitted from the semiconductor laser and the incident end face of the light guide plate 9. The semiconductor lasers 1 a to 1 c are arranged so that the longitudinal direction of 9 a coincides with the incident end face 9 a of the light guide plate 9.

  Thus, the reason why the fast axis direction of the laser beam 10 emitted from the semiconductor laser and the longitudinal direction of the incident end surface 9a of the light guide plate 9 are coincident with each other on the incident end surface 9a of the light guide plate 9 is that the semiconductor laser is in a single mode. This is because the intensity distribution in the fast axis direction is very stable. By matching the fast axis direction of the laser beam 10 having a very stable intensity distribution with the longitudinal direction of the incident end surface 9a of the light guide plate 9, the laser beam having a very stable Gaussian distribution can be converted into the first aspheric lens 6. Can be incident.

  In contrast, when multi-mode oscillation is performed in the slow axis direction, the intensity distribution in the slow axis direction has large individual differences. In addition, when the intensity distribution of the incident laser beam 10 is not a Gaussian distribution, the uniformity of the intensity distribution of the laser beam 10 to be converted also deteriorates.

  For this reason, in the present embodiment, the Y-axis direction in FIG. 2 (the longitudinal direction of the incident end face 9a of the light guide plate 9) and the X-axis direction in FIG. 4 (the slow axis direction of the laser light 10 emitted from the semiconductor laser). When the semiconductor lasers 1a to 1c are arranged so as to coincide with each other on the incident end face 9a of the light guide plate 9, the laser light 10 varies due to the individual difference between the semiconductor lasers 1a to 1c. As a result, the intensity distribution of the laser beam 10 incident on the first aspheric lens 6 changes, and the first aspheric lens 6 cannot stably and uniformly convert the intensity distribution of the laser beam 10.

  Therefore, in the present embodiment, the Y-axis direction in FIG. 2 (the longitudinal direction of the incident end face 9a of the light guide plate 9) and the Y-axis direction in FIG. 4 (the fast axis direction of the laser light 10 emitted from the semiconductor laser) Semiconductor lasers 1 a to 1 c are arranged so as to coincide with each other at the incident end face 9 a of the light guide plate 9. As a result, the intensity distribution of the laser light 10 incident on the first aspherical lens 6 becomes a very stable Gaussian distribution that does not vary due to individual differences among semiconductor lasers. Therefore, the first aspheric lens 6 can stably convert the intensity distribution of the laser light 10 uniformly. As a result, the uniformity of the luminance of the surface light source can be increased.

  The arrangement of the semiconductor lasers 1a to 1c is not limited to the vertical arrangement as shown in FIG. 1, and may be arranged in the horizontal direction. As long as the fast axis direction of the laser light 10 incident on the first aspherical lens 6 is aligned with the longitudinal direction of the incident end surface 9a of the light guide plate 9, the semiconductor lasers 1a to 1c are arranged in any way. May be.

  Next, the details of the first beam shaping lenses 2a to 2c will be described.

  As described above, the first beam shaping lenses 2a to 2c are beam shaping lenses having power only in the X-axis direction. The lens element 2a-1 constituting the first beam shaping lens 2a shown in FIG. 1 converts the laser light from the semiconductor laser 1a-1 into substantially parallel light in the X-axis direction, and the lens element 2a-2 is a semiconductor laser. The laser beam from 1a-2 is converted into substantially parallel light in the X-axis direction. Similarly, the lens element 2b-1 constituting the first beam shaping lens 2b shown in FIG. 1 converts the laser light from the semiconductor laser 1b-1 into substantially parallel light in the X-axis direction, and the lens element 2b-2 The laser light from the semiconductor laser 1b-2 is converted into substantially parallel light in the X-axis direction. The same applies to the first beam shaping lens 2c.

ここで、ｐはマルチストライプ構造の半導体レーザの間隔であり、ｆは第１ビーム成形レンズを構成するレンズ要素の焦点距離である。第１ビーム成形レンズ２ａ〜２ｃから出射されるレーザ光が式（１）に示す発散角θを持つと、導光板９に入射するレーザ光１０の遅軸方向（導光板９の入射端面９ａの短手方向）のビーム径が太くなる。すなわち、導光板９の入射端面９ａの短手方向の幅を、レーザ光１０の遅軸方向のビーム径に応じて厚くする必要がある。 Here, if the first beam shaping lenses 2a to 2c are each constituted by one lens element, the laser beams from the semiconductor lasers 1a to 1c are not converted into substantially parallel beams, but the following formula (1 The divergence angle θ shown in FIG.

Here, p is an interval between semiconductor lasers having a multi-stripe structure, and f is a focal length of lens elements constituting the first beam shaping lens. When the laser beams emitted from the first beam shaping lenses 2a to 2c have a divergence angle θ shown in the formula (1), the slow axis direction of the laser beam 10 incident on the light guide plate 9 (the incident end surface 9a of the light guide plate 9). The beam diameter in the short direction becomes thicker. That is, it is necessary to increase the width in the short direction of the incident end face 9 a of the light guide plate 9 according to the beam diameter in the slow axis direction of the laser light 10.

  On the other hand, in the present embodiment, each of the first beam shaping lenses 2a to 2c is composed of two lens elements. Thereby, each 1st beam shaping lens 2a-2c can convert each laser of the semiconductor lasers 1a-1c of a multi-stripe structure into substantially parallel light individually in the X-axis direction. As a result, since it is not necessary to increase the width of the light guide plate 9, it is possible to reduce the thickness of the surface light emitting device 100 while maintaining the luminance uniformity of the surface light source.

  Next, details of the second beam shaping lenses 3a to 3c will be described.

  As described above, the second beam shaping lenses 3a to 3c are beam shaping lenses having power only in the Y-axis direction. Here, as shown in FIG. 4, the laser emission surfaces 49 of the semiconductor laser having a multi-stripe structure are arranged in the X-axis direction. Therefore, unlike the first beam shaping lenses 2a to 2c, the second beam shaping lenses 3a to 3c having power only in the Y-axis direction do not require the lens elements to be individually arranged for each laser. That is, even when the second beam shaping lenses 3a to 3c are constituted by one lens (for example, a cylindrical lens), the laser beams of the semiconductor lasers 1a to 1c can be changed into substantially parallel beams in the Y-axis direction. it can. In the present embodiment, the case where the second beam shaping lenses 3a to 3c are not divided into lens elements has been described. However, the second beam shaping lenses 3a to 3c may be divided into lens elements and used.

  For example, the focal length of the second beam shaping lens 3a is the average value of the beam diameters in the Y-axis direction in the vicinity of the first aspherical lens 6 of the laser light emitted from the semiconductor laser 1a-1 and the semiconductor laser 1a-2. It is set so as to substantially match the designed incident beam diameter of the first aspheric lens 6. Thereby, even when the divergence angles of the laser beams emitted from the semiconductor laser 1a-1 and the semiconductor laser 1a-2 vary, the intensity distribution in the Y-axis direction of the laser beam 10 on the incident end surface 9a of the light guide plate 9 is uniform. Can be converted to a simple distribution. Specifically, as shown in FIG. 5, the intensity distribution in the Y-axis direction of the laser beam 10 immediately before incidence of the light guide plate 9 is the laser beam intensity distribution 1 indicating the intensity distribution of the semiconductor laser 1a-1 and the semiconductor laser 1a. The laser beam intensity distribution 3 is a combination with the laser beam intensity distribution 2 indicating the intensity distribution of -2. The same applies to the other second beam shaping lenses 3b and 3c. In this way, by setting the focal length of the second beam shaping lenses 3a to 3c, the intensity distribution of the laser light 10 on the incident end face 9a of the light guide plate 9 can be made uniform.

  Thus, in the present embodiment, laser beams emitted from the semiconductor lasers 1a-1 to 1c-2 having a multi-stripe structure using the first beam shaping lenses 2a to 2c and the second beam shaping lenses 3a to 3c. The light is converted into a collimated beam having a beam diameter in the Y direction of A (collimate).

  In general, the interval (dimension) between semiconductor lasers having a multi-stripe structure is several tens of microns (μm) to several hundreds of microns. Here, if the beam shaping lenses 2a to 2c convert the laser beam into a parallel beam not only in the X-axis direction but also in the Y-axis direction, the beam diameter in the Y-axis direction is the interval between the semiconductor lasers. It can no longer be expanded. That is, since the beam diameter of the laser light 10 incident on the first aspheric lens 6 is several hundred microns at the maximum, the design incident beam diameter of the first aspheric lens 6 needs to be several hundred microns. Therefore, in the first aspheric lens 6, the influence of adjustment error (decenter error) and variation in beam diameter on intensity distribution conversion becomes larger.

  On the other hand, if the interval between semiconductor lasers having a multi-stripe structure is increased to several millimeters, the beam diameter in the X-axis direction becomes thick. For example, if 10 semiconductor lasers are arranged at intervals of 5 mm in the X-axis direction, a width of 50 (= 5 mm × 10) mm is required, and thus the surface emitting device 100 itself cannot be thinned.

  On the other hand, in the surface emitting device 100 according to the present embodiment, the first beam shaping lenses 2a to 2c and the second beam shaping lenses 3a to 3c are used to individually perform beam shaping in the X axis direction and the Y axis direction. Do. Thereby, in the surface emitting device 100, even when a semiconductor laser having a multi-stripe structure is used, the width of the device in the X-axis direction is prevented from increasing, and the beam diameter in the Y-axis direction is limited. While preventing this, beam shaping can be performed.

  Further, by configuring both surfaces of the first beam shaping lenses 2a to 2c with cylindrical surfaces (the surface on the laser light source 1 side is configured with a cylindrical surface in the X-axis direction, and the surface on the exit side is configured with a cylindrical surface in the Y-axis direction), It is possible to solve the problem relating to the dimension between the semiconductor lasers having the multi-stripe structure. However, it is known that it is very difficult to suppress the error in the rotation direction about the optical axis of the cylindrical surface in the X-axis direction and the cylindrical surface in the Y-axis direction to a level at which there is no problem in order to operate normally. ing. For this reason, it is very difficult to actually use a beam shaping lens having both cylindrical surfaces.

  On the other hand, in the surface light emitting device 100 according to the present embodiment, the first beam shaping lenses 2a to 2c and the second beam shaping lenses 3a to 3c individually perform beam shaping in the X axis direction and the Y axis direction. Thereby, in the surface light-emitting device 100, the problem which arises when the said lens both surfaces are comprised with a cylindrical surface by the easy structure using the 1st beam shaping lenses 2a-2c and the 2nd beam shaping lenses 3a-3c is considered. Therefore, beam shaping in the X-axis direction and the Y-axis direction can be performed.

<Operation of surface emitting device>
Next, the operation of the surface light emitting device 100 having the above configuration will be described.

  First, the semiconductor lasers 1a to 1c emit red, green, and blue laser beams 10a to 10c, respectively. Laser beams 10a to 10c emitted from the semiconductor lasers 1a to 1c are converted (beam shaped) into parallel beams having a beam diameter A by the corresponding first beam shaping lenses 2a to 2c and second beam shaping lenses 3a to 3c. The The laser beams 10 a to 10 c after the beam shaping are combined into one laser beam 10 by the color combining prism 4. The combined laser beam 10 is bent by the bending mirror 5 and enters the first aspherical lens 6.

  The laser beam 10 incident on the first aspherical lens 6 is converted by the first aspherical lens 6 into an intensity distribution in which the intensity distribution in the Y-axis direction of a parallel beam having a beam diameter A having a Gaussian intensity distribution is uniform. Then, the light enters the second aspheric lens 7. At this time, in the present embodiment, the semiconductor lasers 1a to 1c are arranged so that the fast axis direction of the laser light 10 incident on the incident end surface 9a of the light guide plate 9 and the longitudinal direction of the incident end surface 9a of the light guide plate 9 coincide. To do. For this reason, the intensity distribution of the laser light 10 incident on the first aspherical lens 6 becomes a very stable Gaussian distribution without variations due to individual differences among semiconductor lasers. For this reason, the first aspherical lens 6 can stably convert the intensity distribution of the laser light 10 uniformly. This greatly contributes to improving the uniformity of the luminance of the surface light source.

  Thereafter, the second aspherical lens 7 converts the laser light 10 that has been diverged by the first aspherical lens 6 into parallel light again.

  Thereafter, the cylindrical lens 8 converts parallel light in the X-axis direction of the laser light 10 into convergent light or divergent light. Therefore, the laser light 10 incident on the incident end surface 9a of the light guide plate 9 has a substantially uniform intensity distribution in the Y-axis direction, convergent light or divergent light in the X-axis direction, and substantially parallel light in the Y-axis direction. Become.

  Thereafter, the laser beam 10 emitted from the cylindrical lens 8 enters the light guide plate 9 from the incident end surface 9 a of the light guide plate 9. The laser beam 10 incident on the light guide plate 9 is diffused by the light diffusion layer disposed on the front surface 9b of the light guide plate 9 while propagating through the light guide plate 9 while repeating total reflection. At this time, of the diffused laser light 10, a component of the laser light that enters the front surface 9b of the light guide plate 9 at an angle smaller than the critical angle appears. The laser light component is uniformly emitted from the front surface 9 b of the light guide plate 9. Thereby, the light guide plate 9 emits light in a planar shape.

  Thus, according to the present embodiment, the semiconductor lasers 1a to 1c are arranged so that the fast axis direction of the laser light incident on the incident end face 9a of the light guide plate 9 and the longitudinal direction of the incident end face 9a of the light guide plate 9 coincide. Place. As a result, the intensity distribution of the laser light 10 incident on the first aspherical lens 6 becomes a very stable Gaussian distribution that does not vary due to individual differences among semiconductor lasers. For this reason, the first aspherical lens 6 can stably convert the intensity distribution of the laser light 10 uniformly. As a result, it is possible to improve the luminance uniformity of the surface light source.

  Further, according to the present embodiment, each of the first beam shaping lenses 2a to 2c is divided into a number of lens elements corresponding to the semiconductor lasers 1a to 1c having a multi-stripe structure. Thereby, the first beam shaping lenses 2a to 2c can individually convert the respective laser beams emitted from the semiconductor lasers 1a to 1c having the multi-stripe structure into substantially parallel beams without having a divergence angle. As a result, the intensity distribution of the laser light 10 on the incident end face 9a of the light guide plate 9 becomes uniform, so that the uniformity of the luminance of the surface light source can be improved.

  Furthermore, according to the present embodiment, the first beam shaping lenses 2a to 2c perform beam shaping in the X-axis direction on the laser light emitted from the multi-stripe semiconductor lasers 1a to 1c, and the second beam The molded lenses 3a to 3c perform beam shaping in the Y-axis direction. Thereby, the laser beam 10 can be shaped by individually controlling the beam diameter in the X-axis direction and the Y-axis direction. Specifically, with respect to the X-axis direction of the laser light 10, the beam diameter can be controlled so that the beam diameter in the slow-axis direction does not increase, and with respect to the Y-axis direction of the laser light 10, the beam diameter can be controlled. The beam diameter can be controlled so that the intensity distribution of the laser beam 10 on the incident end face 9a of the optical plate 9 is uniform. As a result, it is possible to improve the luminance uniformity of the surface light source.

  Note that the optical system in the present embodiment can be variously changed.

  For example, instead of the second aspherical lens 7, an aspherical Fresnel having power only in the Y-axis direction is used as an optical system that converts the laser light 10 diverged by the first aspherical lens 6 into substantially parallel light again. A lens can be used. The aspheric Fresnel lens can be made thinner than a normal aspheric lens. Therefore, when an aspheric Fresnel lens is used, the thickness of the lens can be reduced, and the surface light emitting device can be reduced in size.

  Further, for example, a cylindrical Fresnel lens can be used instead of the cylindrical lens 8. The cylindrical Fresnel lens has power only in the X-axis direction, and converts the laser beam 10 into convergent light. The cylindrical Fresnel lens can be made thinner than the cylindrical lens 8. Therefore, when a cylindrical Fresnel lens is used, the thickness of the lens can be reduced, and the surface light emitting device can be reduced in size.

  Furthermore, for example, the aspheric Fresnel lens having power only in the Y-axis direction and the cylindrical Fresnel lens having power only in the X-axis direction may be used at the same time. Thereby, since the thickness of two lenses can be made thin, size reduction of a surface emitting device can be achieved further.

  Further, for example, a diffusion plate can be used instead of the cylindrical lens 8. The diffusing plate has the same function as the cylindrical lens 8 in that the laser beam 10 after passing through the second aspherical lens 7 is given a divergence. In addition, the diffusion plate can be made thinner than the cylindrical lens 8. Therefore, when the diffusion plate is used, the thickness can be reduced, and as a result, the surface light emitting device can be made compact. Further, since the diffusing plate has a higher power in the X-axis direction than the cylindrical lens 8, the luminance in the Z-axis direction can be made uniform.

  In addition, you may comprise so that the laser beam 10 from the 1st aspherical lens 6 may inject into a diffuser plate directly. Thereby, since the 2nd aspherical lens 7 can be abbreviate | omitted, a surface emitting apparatus can be made further compact.

  Further, a diffuser plate and a cylindrical Fresnel lens having power only in the X-axis direction may be used at the same time. As a result, the divergence angle of the laser beam 10 incident on the incident end face 9a of the light guide plate 9 can be increased as compared with the case where a cylindrical Fresnel lens is used alone, and the luminance uniformity in the Z-axis direction is further increased. Can do.

(Embodiment 2)
Next, an image display apparatus according to Embodiment 2 will be described. FIG. 6 is a cross-sectional view showing a schematic configuration of the image display apparatus according to the present embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  An image display device 600 shown in FIG. 6 includes a surface light emitting device 100 corresponding to the first embodiment shown in FIG.

  The display panel 61 is disposed at a position facing the front surface 9 b of the light guide plate 9. The display panel 61 is, for example, a known liquid crystal panel, and includes a polarizing plate, a liquid crystal cell, a color filter, and the like (not shown).

  The image display device 600 makes the laser light 10 emitted from the front surface 9b of the light guide plate 9 enter the display panel 61, and displays an image using light blocking and transmission phenomena by the display panel 61.

  As described above, according to the present embodiment, since the surface light emitting device 100 having high luminance uniformity described in the first embodiment is used as a light source, luminance unevenness can be reduced.

  The surface light-emitting device and the image display device according to the present invention are useful as a surface light-emitting device and an image display device that can improve the uniformity of luminance. In addition, the surface light emitting device and the image display device according to the present invention are suitable for a liquid crystal television, a liquid crystal monitor, and the like where high image quality, small size, and low power consumption are desired.

Sectional drawing which shows schematic structure of the surface emitting apparatus which concerns on Embodiment 1 of this invention. 1 is a cross-sectional view perpendicular to FIG. 1 showing a schematic configuration of the main part of FIG. (A) is a figure which shows an example of the intensity distribution of the Y-axis direction of the laser beam in the entrance surface vicinity of the 1st aspherical lens of FIG. 1, (B) is the position which injects into the 2nd aspherical lens of FIG. Showing an example of intensity distribution in the Y-axis direction of laser light in Schematic showing the general structure of the semiconductor laser of FIG. The figure which shows an example of the intensity distribution of the Y-axis direction of the laser beam in the incident end surface of the light-guide plate of FIG. Sectional drawing which shows schematic structure of the image display apparatus which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Red semiconductor laser 1b Green semiconductor laser 1c Blue semiconductor laser 2a, 2b, 2c 1st beam shaping lens 3a, 3b, 3c 2nd beam shaping lens 4 Color synthesis prism 5 Bending mirror 6 1st aspherical lens 7 2nd aspherical surface Lens 8 Cylindrical lens 9 Light guide plate 9a Incident end face of light guide plate 9b Front surface of light guide plate 9c Back surface of light guide plate 10a Laser light emitted from red semiconductor laser 10b Laser light emitted from green semiconductor laser 10c Laser light emitted from blue semiconductor laser Laser beam synthesized by 10 color synthesis prism 41 Electrode 42 Stripe 43 Oxide film 44 P-type clad layer 45 Active layer 46 N-type clad layer 47 Substrate 48 Electrode 49 Laser emission surface 100 Surface light emitting device 600 Image display device

Claims (12)

A semiconductor laser light source having a multi-stripe structure for emitting a plurality of laser beams;
A light guide plate that guides laser light from the incident surface and emits light from the exit surface; and
A first optical system for converting laser light emitted from the semiconductor laser light source into substantially parallel light in a slow axis direction;
A second optical system for converting laser light emitted from the semiconductor laser light source into substantially parallel light in the fast axis direction;
An intensity distribution converter that converts the intensity distribution of the laser light emitted from the semiconductor laser light source into a substantially uniform intensity distribution in the longitudinal direction of the incident surface of the light guide plate;
The fast axis direction of the laser light converted by the intensity conversion unit incident on the incident surface of the light guide plate coincides with the longitudinal direction of the incident surface of the light guide plate.
Surface emitting device. The first optical system has an array shape including a plurality of lens elements corresponding to a plurality of semiconductor lasers constituting the semiconductor laser light source having the multi-stripe structure.
Each of the plurality of lens elements converts laser light emitted from a corresponding semiconductor laser into substantially parallel light in the slow axis direction.
The surface emitting device according to claim 1. The semiconductor laser light source is
It is composed of a plurality of semiconductor laser light sources having a multi-stripe structure in which the wavelengths of emitted laser light are different from each other,
The fast axis direction of each laser beam incident on the incident surface of the light guide plate coincides with the longitudinal direction of the incident surface of the light guide plate,
The surface emitting device according to claim 1. A light combining unit that combines a plurality of laser beams emitted from the plurality of semiconductor laser light sources having a multi-stripe structure;
The intensity distribution converter is
Converting the intensity distribution of the laser light combined by the light combining section into a substantially uniform intensity distribution in the longitudinal direction of the incident surface of the light guide plate;
The surface emitting device according to claim 3. Laser light that is disposed between the intensity distribution conversion unit and the light guide plate and that is incident on the light guide plate is converted into substantially parallel light with respect to the longitudinal direction of the incident surface of the light guide plate, and / or A third optical system for changing a divergence angle in the short direction of the incident surface;
The surface emitting device according to claim 1, further comprising: The semiconductor laser light source is
Having a plurality of semiconductor laser light sources having a multi-stripe structure for emitting laser light having wavelengths corresponding to the three primary colors;
The surface emitting device according to claim 1. The intensity distribution converter is
Composed of at least one aspheric lens element or aspheric mirror,
The surface emitting device according to claim 1. The third optical system includes:
Using one lens element, the laser light incident on the light guide plate is converted into substantially parallel light in the longitudinal direction of the incident surface of the light guide plate.
The surface emitting device according to claim 7. The third optical system includes:
Using one lens element, the divergence angle in the short direction of the incident surface of the light guide plate is controlled.
The surface emitting device according to claim 7. The third optical system includes:
Using one diffusion plate, changing the divergence angle in the short direction of the incident surface of the light guide plate,
The surface emitting device according to claim 7. The third optical system includes:
Using one lens element and one diffusion plate, changing the divergence angle in the short direction of the incident surface of the light guide plate,
The surface emitting device according to claim 7. A surface light-emitting device according to any one of claims 1 to 11,
A display panel disposed on the light exit surface side of the light guide plate;
An image display apparatus.

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