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 first optical element disposed on the emission side of the light sources and concentrating light emitted from the plurality of light sources; a second optical element disposed on the emission side of the first optical element and tilting the distribution of light concentrated by the first optical element in one direction; and a fourth optical element comprising a combination of a third optical element and spreading the light concentrated by the first optical element in the one direction, wherein the fourth optical element has a contact angle that varies depending on its position within the segment defined by each light source.
• 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 illustrating an example of the configuration of a light distributing lens according to an embodiment.
• FIG. 3A is a diagram showing an example of a luminance distribution by a composite prism according to a comparative example.
• FIG. 3B is a diagram showing an example of a luminance distribution by a composite prism according to a comparative example.
• FIG. 4A is a diagram showing an example of relative luminance obtained by a composite prism according to a comparative example.
• FIG. 4B is a diagram showing an example of relative luminance obtained by a composite prism according to a comparative example.
• FIG. 4A is a diagram showing an example of relative luminance obtained by a composite prism according to a comparative example.
• FIG. 4B is a diagram showing an example of relative luminance obtained by a composite prism according to a comparative example.
• FIG. 1 is
• FIG. 5 is a diagram for explaining the decrease in luminance in the partial region S1 on the upper side in the front direction.
• FIG. 6 is a diagram for explaining the continuous change in the contact angle depending on the position of the composite prism according to the embodiment.
• FIG. 7A is a diagram illustrating an example of a luminance distribution by a composite prism according to an embodiment.
• FIG. 7B is a diagram illustrating an example of a luminance distribution by a composite prism according to the embodiment.
• FIG. 8A is a diagram illustrating an example of relative luminance obtained by a composite prism according to the embodiment.
• FIG. 8B is a diagram illustrating an example of relative luminance obtained by the composite prism according to the embodiment.
• FIG. 9A is a diagram for explaining the effect of the planar illumination device according to the embodiment.
• FIG. 9B is a diagram for explaining the effect of the planar illumination device according to the embodiment.
• FIG. 1 is a diagram showing 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 assumed to be in the X-Y plane, and the thickness direction of the surface lighting device 1 is assumed to be the Z direction.
• the X-axis direction corresponds to the horizontal direction (H) and the Y-axis direction corresponds to the vertical direction (V).
• the use state of the surface lighting device 1 is not limited to the above directions, and it 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 roughly 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 in multiple numbers on the substrate 3 in a two-dimensional pattern (e.g., a grid pattern). Light sources 4 with a light distribution pattern known as a top hat pattern are suitable. Each of the multiple light sources 4 can be 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 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 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 (corresponding to the first optical element) with concave and convex grooves extending along the X-axis direction in the output surface.
• the linear Fresnel lens has grooves that are periodically formed to match the spacing (pitch) between the multiple light sources 4.
• the light distributing lens 7 is an optical element disposed on the exit side of the collecting lens 6, and tilts the distribution of light collected by the collecting lens 6 in the Y-axis direction.
• the light distributing lens 7 has a compound prism that combines, within its incident surface, a linear prism with concave and convex grooves extending along the X-axis direction and a lenticular lens with concave and convex grooves extending along the X-axis direction.
• the light distributing lens 7 also has a lenticular lens with concave and convex grooves extending along the Y-axis direction within its exit surface.
• the composite prisms in this embodiment have a pitch smaller than the pitch of the light sources 4 (i.e., there are multiple composite prisms within one segment), and have different contact angles depending on their position in the Y-axis direction within the segment S defined by each light source 4.
• An example configuration and contact angle of the light distribution lens 7 will be described in detail later.
• 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
• FIG. 2 is a diagram illustrating an example configuration of a light distributing lens 7 according to an embodiment.
• the right side of FIG. 2 illustrates an example of a light distributing lens 7 according to an embodiment.
• the left side of FIG. 2 illustrates an example of a light distributing lens 7' according to a comparative example. Note that the "upper side” on the paper surface of FIG. 2 corresponds to the "upper side” when the planar lighting device 1 is in use, and the "lower side” on the paper surface of FIG. 2 corresponds to the "lower side” when the planar lighting device 1 is in use.
• linear prism 71a and linear prism 71b are referred to collectively without distinction, they will be referred to as “linear prism 71.”
• lenticular lens 72a and lenticular lens 72b are referred to collectively without distinction, they will be referred to as “lenticular lens 72.”
• composite prism 73a and composite prism 73b are referred to collectively without distinction, they will be referred to as "composite prism 73.”
• a composite prism 73 corresponding to a fourth optical element
• combines a linear prism 71 (corresponding to a second optical element) with a triangular cross section that tilts the distribution of light collected by the collecting lens 6 in the Y-axis direction (for example, tilting in the V -12° direction)
• a lenticular lens 72 corresponding to a third optical element
• the composite prism 73 is an optical element in which lenticular lenses 72 extending along the X-axis direction are formed on the main surface of the linear prism 71 that extends along the X-axis direction, and multiple composite prisms 73 are arranged in the Y-axis direction.
• the main surface of the linear prism 71 is the inclined surface with the smaller inclination angle of a pair of inclined surfaces.
• the lenticular lens 72 is formed as a curved surface (arc-shaped cross section) with a constant curvature R that is convex outward, starting from the vertex side of the main surface of the linear prism 71.
• Figure 2 shows a boundary line between the linear prism 71 and the lenticular lens 72, in reality there is no boundary line because the two are molded as a single unit.
• the light distribution lens 7' also has a composite prism 73' that combines a linear prism 71' and a lenticular lens 72'.
• the basic configurations of the linear prism 71', lenticular lens 72', and composite prism 73' are similar to those of the linear prism 71, lenticular lens 72, and composite prism 73, so a description thereof will be omitted.
• the height H and pitch length L of all composite prisms 73' in the light distributing lens 7' according to the comparative example are constant at any position within the segment S. Therefore, the contact angle, which is the angle between the curved surface of the lenticular lens 72' in the composite prism 73' and the plane of the base portion (X-Y plane) of the light distributing lens 7', is uniform regardless of the composite prism 73'.
• the light distributing lens 7 has different contact angles depending on the position within the segment S.
• the contact angle ⁇ a of the composite prism 73a is greater than the contact angle ⁇ b of the composite prism 73b.
• the larger the contact angle the greater the degree of diffusion of light passing through the curved surface, and therefore the degree of diffusion of light exiting from the composite prism 73a is greater than the degree of diffusion of light exiting from the composite prism 73b.
• the contact angle of the composite prism 73 can be freely changed (designed) by varying the height to the apex of each prism, since the curvature of the curved surface is constant.
• the height of each composite prism 73 can be varied by varying the depth of the tool (bite) used to cut the uneven surface of each composite prism 73.
• the contact angle varies depending on the height (depth of the mold groove), and the higher the height (deeper the mold groove), the larger the contact angle.
• the contact angle ⁇ a can be designed to be larger than the contact angle ⁇ b.
• the contact angle is calculated using, for example, the ⁇ /2 method, but any known calculation method can be applied as appropriate.
• the pitch length Lb of the composite prism 73b is also ⁇ l shorter than the length La. For this reason, it is preferable to arrange the composite prisms 73a and 73b closely together so that no flat area (a portion where the composite prism 73 is not arranged) is created between them.
• Figures 3A and 3B are diagrams showing an example of the luminance distribution by a composite prism 73' according to a comparative example.
• Figures 4A and 4B are diagrams showing an example of the relative luminance by a composite prism 73' according to a comparative example.
• "S" indicates a segment
• S1 indicates the upper partial region of segment S
• S2 indicates the lower partial region of segment S.
• Figures 4A and 4B illustrate the relative luminance for each position in the H and V directions.
• Figure 5 is a diagram explaining the decrease in brightness in the upper partial area S1 in the front direction.
• the preceding focusing lens 6 is designed to be symmetrical up and down about the optical axis and to somewhat broaden (defocus) the light beam.
• the upper partial area S1 emits light that is mainly directed upward
• the lower partial area S2 emits light that is mainly directed downward.
• the composite prism 73 in this embodiment is configured to have different contact angles and different heights (vertex positions) depending on its position within the segment S.
• Figure 6 is a diagram for explaining the continuous change in contact angle depending on the position of the composite prism 73 in this embodiment.
• Figure 6 illustrates a graph showing the magnitude of the contact angle relative to the vertex position of the composite prism 73 in the Y-axis direction.
• the contact angle of the composite prism 73 in partial region S1 is configured to be smaller than in other regions.
• the minimum contact angle in partial region S1 is 15.2 degrees. This reduces the degree of diffusion in partial region S1, which is expected to improve brightness and eliminate the dark lines that occurred in composite prism 73'.
• the contact angle of the composite prism 73 near the center is configured to be larger compared to other regions.
• the maximum contact angle near the center is 15.9 degrees. This increases the degree of diffusion near the center, which is expected to reduce brightness near the center and improve brightness uniformity in segment S.
• the contact angle of the composite prism 73 below the optical axis is configured to be larger overall compared to above the optical axis. This is because the brightness below the optical axis tends to be greater than above. In other words, this configuration increases the degree of diffusion below the optical axis, which is expected to reduce the brightness below the optical axis and improve brightness uniformity in segment S.
• the contact angle of the composite prism 73 in the partial region S2 is smaller than near the center, but larger than in other regions. This increases the degree of diffusion in the partial region S2, which is expected to reduce the brightness of the partial region S2 and improve the bright lines that occurred in the composite prism 73'.
• Figures 7A and 7B are diagrams showing an example of the luminance distribution by the composite prism 73 according to the embodiment.
• Figures 8A and 8B are diagrams showing an example of the relative luminance by the composite prism 73 according to the embodiment.
• Figures 8A and 8B illustrate the relative luminance for each position in the H direction and V direction.
• the brightness fluctuation range was small in both the front and oblique directions, and it was found that the bright and dark lines that appeared in the comparative example (composite prism 73') were improved.
• FIGS. 9A and 9B are diagrams illustrating the effects of the surface lighting device 1 according to the embodiment.
• FIG. 9A and 9B illustrate the results of a comparison of the relative luminance of the composite prism 73 (surface lighting device 1) and the relative luminance of the composite prism 73' (comparison example) with a focus on the V-section.
• the planar lighting device comprises a plurality of light sources; a first optical element disposed on the emission side of the light sources and concentrating light emitted from the plurality of light sources; a second optical element disposed on the emission side of the first optical element and tilting the distribution of light concentrated by the first optical element in one direction; and a fourth optical element comprising a third optical element that spreads the light concentrated by the first optical element in the one direction, the fourth optical element having a contact angle that varies depending on its position within the segment defined by each light source.
• the one direction is a first direction (e.g., the Y-axis direction)
• the fourth optical element is an optical element in which the second optical element has a triangular cross-section extending along a second direction (e.g., the X-axis direction) perpendicular to the optical axis of the light and the first direction
• the third optical element has an arc-shaped cross-section extending along the second direction, formed on one surface of the second optical element.
• the fourth optical elements are arranged in multiple rows in the one direction, and the multiple fourth optical elements have different contact angles due to the fact that the curvature of the curved surface of the third optical element is constant and the height to the apex of each fourth optical element varies depending on the position in the one direction within the segment. This makes it possible for the surface lighting device to improve non-uniformity in brightness, particularly in the one direction.
• the plurality of fourth optical elements have a large contact angle near the center in the one direction within the segment. This increases the degree of diffusion near the center, thereby suppressing the brightness near the center and improving brightness uniformity within the segment S.
• the plurality of fourth optical elements have a small contact angle near the end (partial region S1) of the segment on the side opposite the tilt direction of the second optical elements (e.g., the lower side/negative Y-axis direction). This reduces the degree of diffusion near the end, improving brightness and eliminating the dark lines that appeared in the comparative example.
• the contact angle of the plurality of fourth optical elements on the side in the tilt direction of the second optical element within the segment is larger than the contact angle on the opposite side (upper side) from the tilt direction. This increases the degree of diffusion below the optical axis, thereby reducing the brightness below the optical axis and improving brightness uniformity within the segment.
• the plurality of fourth optical elements have a large contact angle near the end of the segment on the side in the tilt direction of the second optical element (partial region S2). This increases the degree of diffusion in partial region S2, thereby reducing the brightness of partial region S2 and improving the bright lines that occurred in the comparative example.
• the multiple light sources are arranged in a grid pattern. This makes it easier to support local dimming drive, and the fourth optical elements, which are positioned according to the position of each light source, can be arranged in a regular pattern, thereby efficiently improving bright lines and dark lines.
• each of the multiple light sources is surrounded by the reflecting surface of the reflector in a rectangular shape to define the segment. This improves contrast when the multiple light sources are driven with local dimming, and also allows the fourth optical element, which is positioned according to the position of each light source, to be optimally positioned for each segment, effectively 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.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Planar Illumination Modules (AREA)
• Optical Elements Other Than Lenses (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=97870268

Family Applications (1)

Country Status (2)

Citations (2)

• 2024
  • 2024-05-27 JP JP2024085371A patent/JP7851357B2/ja active Active
• 2025
  • 2025-05-13 WO PCT/JP2025/017368 patent/WO2025249144A1/ja active Pending

Patent Citations (2)

Also Published As

Similar Documents

Legal Events