Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
  • F21S2/00—Systems of lighting devices, not provided for in main groups F21S4/00 - F21S10/00 or F21S19/00, e.g. of modular construction

Definitions

• the present invention relates to a surface lighting device.
• Direct-type planar lighting devices which have a substrate on which multiple light sources are arranged two-dimensionally, and a reflector arranged on this substrate with a reflective surface surrounding the emission side of each light source.
• light from the light source is focused by a linear Fresnel lens with concave and convex grooves extending in one direction (e.g., the horizontal or lateral direction when the user views the emission surface directly or indirectly), and the optical axis is tilted by a peak-shift prism with concave and convex grooves extending in the same direction as the linear Fresnel lens, thereby achieving a narrow light distribution in a direction perpendicular to the grooves (e.g., the vertical or longitudinal direction).
• Direct-type planar lighting devices equipped with a linear Fresnel lens and a peak-shift prism are used, for example, in head-up displays (HUDs), which require high brightness.
• display devices including HUDs
• H directly in front
• the backlight surface lighting device that illuminates the LCD panel used as the display device is required to be able to look good from both directions while improving the uniformity of brightness in each direction.
• various methods for improving surface lighting devices have been proposed, but further improvements are desired.
• the problem that this invention aims to solve is to provide a surface lighting device that can improve the uniformity of brightness in each direction while maintaining a good appearance from two directions.
• one aspect of the present invention provides a surface lighting device comprising: a plurality of light sources; a reflector having a reflective surface surrounding the emission side of each of the plurality of light sources; a focusing lens disposed on the emission side of the reflector for focusing light emitted from the plurality of light sources; and a light distribution lens disposed on the emission side of the focusing lens for tilting the distribution of light focused by the focusing lens in one direction, wherein the apex of the reflector is positioned at a position offset from the center position of two adjacent light sources in the one direction.
• FIG. 1 is a diagram illustrating an example of the configuration of a surface illumination device according to an embodiment.
• FIG. 2 is a diagram showing an example of the behavior of light rays when the reflector according to Comparative Example A is used.
• FIG. 3 is a diagram illustrating an example of the behavior of light rays when the reflector according to the embodiment is used.
• FIG. 4A is a diagram illustrating a luminance distribution when a reflector according to a comparative example is used.
• FIG. 4B is a diagram illustrating a luminance distribution when the reflector according to the embodiment is used.
• FIG. 5 is a diagram for explaining the effect of the reflector according to the embodiment.
• FIG. 6 is a diagram for explaining the asymmetric structure of the condenser lens according to the embodiment.
• FIG. 1 is a diagram illustrating an example of the configuration of a surface illumination device according to an embodiment.
• FIG. 2 is a diagram showing an example of the behavior of light rays when the reflector according to Compar
• FIG. 7 is a diagram for explaining the asymmetric structure of the condenser lenses according to the comparative examples B1 to B4.
• FIG. 8A is a diagram illustrating a luminance distribution when a condenser lens according to a comparative example is used.
• FIG. 8B is a diagram illustrating a luminance distribution when the condenser lens according to the embodiment is used.
• FIG. 9 is a diagram for explaining the effect of the condenser lens according to the embodiment.
• FIG. 10A is a diagram illustrating the luminance distribution of a surface illumination device according to a comparative example.
• FIG. 10B is a diagram illustrating a luminance distribution of the planar illumination device according to the embodiment.
• FIG. 11 is a diagram for explaining the effect of the planar illumination device according to the embodiment.
• FIG. 12A is a diagram illustrating the luminance distribution of a surface illumination device according to a comparative example.
• FIG. 12B is a diagram illustrating a luminance distribution of the planar illumination device according to the embodiment.
• FIG. 13 is a diagram for explaining the effect of the planar illumination device according to the embodiment.
• FIG. 1 is a diagram illustrating an example of the configuration of a surface lighting device 1 according to an embodiment, and is an end view showing the state within the thickness.
• the light-emitting surface of the surface lighting device 1 is in the X-Y plane, and the thickness direction of the surface lighting device 1 is defined as the Z-axis direction.
• the X-axis direction corresponds to the horizontal direction (H) and the Y-axis direction corresponds to the vertical direction (V).
• the positive direction of the Y-axis corresponds to the "upper side” and the negative direction of the Y-axis corresponds to the "lower side.”
• the usage state of the surface lighting device 1 is not limited to the above-mentioned direction and can be used in any direction.
• the surface lighting device 1 includes a bottom frame 2, a substrate 3, a light source 4, a reflector 5, a condenser lens 6, a light distribution lens 7, and a reflective polarizing film 8.
• the bottom frame 2 is a generally box-shaped member with a bottom that houses the substrate 3 (described below) and other components.
• the bottom frame 2 is fitted with a top frame (not shown) that has an opening for emitting light, thereby forming the exterior of the surface lighting device 1.
• the bottom frame 2 is appropriately provided with structures (protrusions, holes, etc.) for housing the substrate 3 and other components, as well as connectors for electrical connection.
• the substrate 3 is provided at the bottom of the bottom frame 2 and is a component that includes electronic components such as the light source 4, which will be described later.
• the light sources 4 are composed of LEDs (Light Emitting Diodes) or the like, and are arranged two-dimensionally (e.g., in a grid pattern) on the substrate 3. Light sources 4 with a light distribution pattern known as a top hat type are suitable. Each of the multiple light sources 4 is driven individually, enabling so-called local dimming drive.
• the reflector 5 is arranged on the side of the substrate 3 where the light sources 4 are arranged, and includes a reflective wall 51 extending along the Y-axis direction and a reflective wall 52 extending along the X-axis direction.
• the reflective walls 51 and 52 of the reflector 5 are arranged at equal intervals between each of the multiple light sources 4, forming a reflective surface that rectangularly surrounds the emission side of each light source 4. This improves contrast when the multiple light sources 4 are driven using local dimming.
• the unit area into which the individual light sources 4 are separated by the reflector 5 is referred to as a "segment (or zone)."
• the height of the reflector 5 can be set arbitrarily, but it is preferable for the reflective wall 52 to be higher than the reflective wall 51, as shown, to reduce stray light.
• the apex of the reflector 5 in this embodiment is positioned in a position offset in the Y-axis direction from the center position of two adjacent light sources 4, and the inclination angles (absolute values) of the reflective surfaces 52a and 52b relative to the optical axis (axis parallel to the Z-axis) are different.
• the inclination angle of the reflective surface 52a is configured to be smaller than the inclination angle of the reflective surface 52b, the apex of the reflector 5 is positioned in a position offset toward the negative Y-axis direction (downward).
• An example configuration of the reflector 5 will be described in detail later.
• the condenser lens 6 is an optical element that is disposed on the output side of the reflector 5 and condenses light from the light source 4 in the Y-axis direction.
• the condenser lens 6 is an optical element that has a lenticular lens with concave and convex grooves extending along the Y-axis direction in the incident surface, and a linear Fresnel lens with concave and convex grooves extending along the X-axis direction in the output surface.
• the linear Fresnel lens has grooves formed periodically to match the spacing (pitch) between the multiple light sources 4.
• the linear Fresnel lens of the condenser lens 6 in this embodiment is an asymmetric Fresnel lens with a different defocus ratio depending on the region in the Y-axis direction.
• An example configuration of the condenser lens 6 will be described in detail later.
• the light distribution lens 7 has a peak-shift prism with concave and convex grooves extending along the X-axis direction on the entrance surface, and a lenticular lens with concave and convex grooves extending along the Y-axis direction on the exit surface.
• the light distribution lens 7 may be equipped with a composite prism that combines the functions of a linear prism that tilts light and a lenticular lens that expands light, as disclosed in, for example, JP 2023-127243 A.
• the reflective polarizing film 8 is an optical component that is placed on the output side of the light distribution lens 7 and improves the brightness of the emitted light.
• the reflective polarizing film 8 is made of, for example, a roughly plate-shaped DBEF (Dual Brightness Enhancement Films), and has polarization that matches the liquid crystal panel provided on the output side of the surface lighting device 1.
• DBEF Double Brightness Enhancement Films
• the reflector 5 has an asymmetric shape in which the inclination angles of a pair of reflective surfaces (reflective surface 52a and reflective surface 52b) in the Y-axis direction (the direction in which the light distribution is inclined by the peak shift prism) are different from each other.
• the inclination angle of reflective surface 52a (corresponding to the first reflective surface) is configured to be smaller than the inclination angle of reflective surface 52b (corresponding to the second reflective surface), so that the apex of the reflector 5 is positioned shifted toward the negative Y-axis direction (downward). This is expected to increase the dominance of light that is incident on the light distributing lens 7 during segment S and that travels downward (toward the negative Y-axis direction, the side in which the light distribution is inclined by the peak shift prism), thereby increasing brightness.
• Reflector 5' has a shape that is symmetrical in the Y-axis direction, and the inclination angles of the pair of reflecting surfaces are the same (the absolute values of the angles are the same).
• Figure 2 is a diagram showing an example of the behavior of light rays when a reflector 5' according to Comparative Example A is used. Figure 2 illustrates the behavior of light rays that arrive at segment S directly from the light source 4 without passing through the reflector 5'.
• the multiple principal surfaces 71 of the light distribution lens 7 are not symmetrical with respect to the optical axis of the light source 4, but are tilted in one direction with respect to the Y-axis direction (the up-down direction in the figure), and the tilt angle is constant in the Y-axis direction. Therefore, the difference in behavior between light rays traveling below the optical axis of the light source 4 and light rays traveling above the optical axis becomes greater as they approach the edge of segment S.
• Figure 3 is a diagram showing an example of the behavior of light rays when a reflector 5 according to an embodiment is used. Figure 3 illustrates the behavior of light rays that reach segment S directly without passing through reflector 5.
• the light rays traveling from the light source 4 toward the edge of the reflector 5 are inferior to the light traveling upward compared to Figure 2, and light traveling downward is dominant, due to the top of the reflector 5 being shifted downward.
• the light incident on the main surface 71 is more dominant than the light incident on the raised surface 72, which is expected to properly demonstrate the light distribution performance of the light distribution lens 7 and improve bright lines and dark lines at the edge of segment S.
• FIG. 4A is a diagram illustrating the luminance distribution when a reflector according to a comparative example is used.
• FIG. 4B is a diagram illustrating the luminance distribution when a reflector according to an embodiment is used.
• FIG. 5 is a diagram for explaining the effect of reflector 5 according to an embodiment.
• FIG. 5 illustrates the results of comparing the relative luminance at the V cross section of FIGS. 4A and 4B. Note that the condenser lens 6, described below, is not applied in FIGS. 4A, 4B, and 5.
• the configuration in which the apex of the reflector is shifted downward is not limited to being achieved by making the inclination angle of reflective surface 52a smaller than the inclination angle of reflective surface 52b.
• the apex of a reflector that is symmetrical in the Y-axis direction i.e., a reflector with the same shape as reflector 5'
• the condenser lens 6 has an asymmetric linear Fresnel lens with a different defocus ratio depending on the region in the Y-axis direction, which allows an appropriate defocus ratio to be set for each region, and is expected to have the effect of improving the luminance distribution for each region.
• FIG. 6 is a diagram illustrating the asymmetric structure of the collecting lens 6 according to the embodiment. Note that FIG. 6 also illustrates a configuration related to the explanation of the asymmetric structure of the collecting lens 6.
• the arrows between the collecting lens 6 and the light distributing lens 7 represent light rays, and the direction of the arrows (angle relative to the optical axis of the light source 4) represents the defocus ratio (degree of light concentration) of the collecting lens 6.
• the distance between the collecting lens 6 and the light distributing lens 7 is shown widened in order to illustrate the arrows indicating light rays.
• the linear Fresnel lens of the collecting lens 6 has different defocus rates in region 61 below the optical axis and region 62 above the optical axis; specifically, it is configured so that the defocus rate in region 61 is smaller than the defocus rate in region 62.
• the light emitted from region 61 has a higher degree of concentration than the light emitted from region 62.
• a high degree of concentration means that the angle of incidence with respect to the imaginary principal plane of the light distribution lens 7 is closer to perpendicular.
• the asymmetric structure of the condenser lens 6 is based on the verification results of comparative examples B1 to B4, in which the defocus ratio of each region was changed.
• Figure 7 is a diagram illustrating the asymmetric structure of the collecting lenses in comparative examples B1 to B4. Note that Figure 7 also illustrates configurations relevant to the explanation of the asymmetric structure of the collecting lens 6.
• the arrows (dashed and solid lines) between the collecting lens 6 and the light distributing lens 7 represent light rays, and the direction (angle) of the arrows represents the defocus ratio (degree of light concentration) of the collecting lens 6.
• the dashed arrows represent light rays collected at a typical defocus ratio
• the solid arrows represent light rays collected at a defocus ratio changed (set) in the comparative example.
• the distance between the collecting lens 6 and the light distributing lens 7 is shown wider in order to illustrate the arrows indicating the light rays.
• the collecting lens 6-1 of Comparative Example B1 has an increased defocus ratio in the upper (non-tilt direction) region.
• the collecting lens 6-2 of Comparative Example B2 has a decreased defocus ratio in the upper (non-tilt direction) region.
• the collecting lens 6-3 of Comparative Example B3 has an increased defocus ratio in the lower (tilt direction) region.
• the collecting lens 6-4 of Comparative Example B4 has a decreased defocus ratio in the lower (tilt direction) region.
• Comparative Example B1 As shown in Table 1, in Comparative Example B1, the brightness distribution in the oblique directions improved, but the brightness distribution in the front direction deteriorated, resulting in prominent dark lines. In Comparative Example B2, the bright and dark lines in the brightness distribution in the front direction improved, but the brightness distribution in the oblique directions deteriorated, resulting in the dark areas in particular becoming larger. In Comparative Example B3, the brightness distribution in both the front and oblique directions deteriorated, resulting in prominent bright lines in the front direction. In Comparative Example B4, the brightness distribution in the front direction improved, the bright lines were weakened, and there was little impact on the brightness distribution in the oblique directions.
• a condenser lens 6 was found that has a linear Fresnel lens with an asymmetric structure (a structure in which the defocus rate is asymmetric with respect to an imaginary plane including the optical axis of the light source) in which the defocus rate in region 61 is smaller than a typical value and the defocus rate in region 62 is about the same as a typical value.
• the "typical defocus rate” will vary depending on the configuration of other optical components, it is preferable to derive it as a value that results in an optimal luminance distribution when using a linear Fresnel lens with a constant defocus rate in the Y-axis direction.
• FIG. 8A is a diagram illustrating the luminance distribution when a condenser lens according to a comparative example is used.
• FIG. 8B is a diagram illustrating the luminance distribution when a condenser lens according to an embodiment is used.
• FIG. 9 is a diagram for explaining the effect of the condenser lens 6 according to an embodiment.
• FIG. 9 illustrates the results of comparing the relative luminance at the V cross section of FIGS. 8A and 8B.
• condenser lens 6' is an optical element having a lenticular lens similar to condenser lens 6 and a linear Fresnel lens with a constant defocus ratio in the Y-axis direction. Also, reflector 5 is not applied in FIGS. 8A, 8B, and 9.
• FIG. 10A is a diagram illustrating the luminance distribution of a planar lighting device according to a comparative example.
• FIG. 10B is a diagram illustrating the luminance distribution of a planar lighting device according to an embodiment.
• FIG. 11 is a diagram for explaining the effect of the planar lighting device according to the embodiment.
• FIG. 12A is a diagram illustrating the luminance distribution of a planar lighting device according to a comparative example.
• FIG. 12B is a diagram illustrating the luminance distribution of a planar lighting device according to an embodiment.
• FIG. 13 is a diagram for explaining the effect of the planar lighting device 1 according to the embodiment.
• FIGS. 10A is a diagram illustrating the luminance distribution of a planar lighting device according to a comparative example.
• FIG. 10B is a diagram illustrating the luminance distribution of a planar lighting device according to an embodiment.
• FIG. 11 is a diagram for explaining the effect of the planar lighting device according to the embodiment.
• the planar lighting device 1 according to the embodiment is configured to include the reflector 5 and condensing lens 6 described above, while the comparative example is configured without the reflector 5 and condensing lens 6, i.e., includes a reflector 5′ and condensing lens 6′.
• FIG. 11 illustrates the results of a comparison of relative luminance in the V cross section of FIGS. 10A and 10B.
• FIG. 13 illustrates the results of a comparison of relative luminance in the V cross section of FIGS. 12A and 12B.
• the planar lighting device comprises a plurality of light sources, a reflector having a reflective surface surrounding the emission side of each of the plurality of light sources, a condensing lens disposed on the emission side of the reflector for condensing light emitted from the plurality of light sources, and a light distribution lens disposed on the emission side of the condensing lens for tilting the distribution of light condensed by the condensing lens in one direction, with the apex of the reflector positioned at a position offset from the center positions of two adjacent light sources in the one direction.
• the planar lighting device can increase the dominance of light incident on the light distribution lens in one direction (e.g., downward/negative Y-axis direction) during segmentation, thereby increasing brightness.
• the apex of the reflector is positioned offset from the center position of the two adjacent light sources in the tilt direction (e.g., downward/negative Y-axis direction) caused by the light distribution lens. This allows the surface lighting device to maximize the light distribution performance of the light distribution lens by increasing the dominance of light directed in the tilt direction caused by the light distribution lens (peak shift prism), thereby improving bright lines and dark lines at the edges of the segments S.
• the reflector has a pair of reflective surfaces with different inclination angles. This allows the surface lighting device to increase the dominance of light that enters the light distribution lens in one direction (e.g., downward/negative Y-axis direction) during segmentation, thereby increasing brightness.
• the angle of inclination of the first reflecting surface of the reflector, located on the side of the inclination direction of the light distribution lens, relative to the optical axis is smaller than the angle of inclination of the second reflecting surface, located on the opposite side of the first reflecting surface, relative to the optical axis.
• the condenser lens is an asymmetric Fresnel lens with a different defocus ratio depending on the region. This allows the surface lighting device to set an appropriate defocus ratio depending on the region, improving the brightness distribution in each region.
• the focusing lens has a small defocus ratio in the area on the tilt direction side of the light distribution lens. This allows the surface lighting device to weaken the bright lines in the area on the tilt direction side (lower side).
• the planar lighting device comprises a plurality of light sources; a reflector having an inclined reflective surface surrounding the emission side of each of the plurality of light sources; a condensing lens disposed on the emission side of the reflector for condensing light emitted from the plurality of light sources; and a light distribution lens disposed on the emission side of the condensing lens for inclining the distribution of light condensed by the condensing lens in one direction, the condensing lens being an asymmetric Fresnel lens with a different defocus ratio depending on the region.
• the planar lighting device can increase the dominance of light incident on the light distribution lens in the inclined direction during segmentation, thereby increasing brightness.
• the multiple light sources are arranged in a grid pattern. This makes it easy to support local dimming drive, and the reflective walls of the reflector placed between each light source can be formed regularly, efficiently improving bright lines and dark lines.
• the present invention is not limited to the above-described embodiments.
• the present invention also includes configurations that appropriately combine the above-described components.
• further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-described embodiments, and various modifications are possible.

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Citations (2)

• 2024
  • 2024-05-27 JP JP2024085372A patent/JP2025178643A/ja active Pending
• 2025
  • 2025-05-13 WO PCT/JP2025/017369 patent/WO2025249145A1/ja active Pending

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