JP2021197324A - Luminaire - Google Patents

Abstract

To provide a luminaire that improves light utilization efficiency more and minimizes electric power that a light source uses for lower power consumption, and is advantageously applied to a backlight device for a liquid crystal display or an illumination type signboard, etc.SOLUTION: A luminaire consists of a surface light source 1, first, second toroidal lenses 2, 3, a reflection mirror 8, and a reflection prism sheet 9. The surface light source is arranged nearby one (Fyz) of two front-side focuses of a composite lens system 5 of the first, second toroidal lenses which is closer to the first toroidal lens 2 and before the other one (Fxz) which is farther. The distance between the second toroidal lens and the reflection mirror is substantially equal to a focal length f2 of the reflection mirror, which is inclined to a z axis. Emitted luminous flux from the composite lens system is reflected by the reflection mirror, and further the reflection prism sheet changes the optical path.SELECTED DRAWING: Figure 1

Description

The present invention relates to a lighting device that is advantageously applied to a backlight device for a liquid crystal display, a lighting type signboard, or the like.

Liquid crystal displays are expanding not only to televisions but also to many application fields such as in-vehicle monitors and medical monitors. Further, it is considered that the liquid crystal display will be applied to a naked-eye stereoscopic display using high-resolution pixels as the resolution of the liquid crystal panel increases to 4K and 8K.

Existing backlight devices used in liquid crystal displays have been developed with a focus on providing a uniform display surface from any angle. On the other hand, since the idea of emitting image light only to the place where the observer is present and reducing the useless image light emitted to other areas to save power has become widespread, the image light is emitted from the display surface with a lumbar cyan. There are an increasing number of existing backlight devices that stop emitting light and utilize a diffuser film and a reflective prism sheet to reduce the amount of image light emitted from the display surface in the vicinity of the horizontal direction as much as possible. However, with an in-vehicle monitor, only the driver needs to see the display surface, so the image light only needs to be emitted near the driver's eyes, which is still useless with the existing backlight device. Image light cannot be eliminated. In order to realize a backlight device that can eliminate useless image light with an existing one, it is necessary to absorb the overspread image light with a black mask or a louver and emit only the narrowed image light. Therefore, it is difficult to save power because the existing backlight device cannot eliminate the absorbed useless image light.

Therefore, as a result of systematically examining the difference in the main ray direction of the image light emitted from the display surface of the liquid crystal display in the field of liquid crystal display application, the present inventors systematically examined the existing backlight device (as shown in FIG. 11). It has been clarified that, unlike FIG. 11 (a)), a so-called parallel light backlight device (FIGS. 11 (b) to (d)) capable of emitting light having the same brightness in the same direction is required. If this parallel light backlight device can be realized, it will be possible to reduce unnecessary image light and improve light utilization efficiency, minimize the power consumption of the light source, and reduce power consumption. We have found that it can be easily developed into a stereoscopic display. After that, as a result of repeated studies, the backlight device described in Patent Document 1 (hereinafter, also referred to as "device of Patent Document 1") was invented as an equivalent to the parallel light backlight device.

The apparatus of Patent Document 1 has a two-dimensional light source having a light emitting source composed of a light emitting diode, a light shaping means for shaping the light emitted from the light emitting source and emitting it as a light beam, and a first condensing light having a focal distance f1. It comprises a bilateral telecentric optical system formed of an optical system and a second condensing optical system having a focal distance f2 larger than the focal distance f1, and further, an optical path changing means, and emits light from the light emitting source of the optical shaping means. The area of the cross section perpendicular to the optical axis of the light beam at the end on the side where the light is incident is perpendicular to the optical axis of the light beam at the end on the side where the light beam is emitted from the optical shaping means. The first condensing optical system is a lens system provided on the side of the two-dimensional light source with respect to the second condensing optical system, which is smaller than the area of the cross section, and the second condensing optical system is a reflection. It is composed of a mirror system, and the emission direction of the light beam emitted from the second condensing optical system is inclined with respect to the optical axis of the light beam passing through the first condensing optical system, and the optical path changing means further comprises. It is characterized in that it is composed of a reflective prism sheet (also referred to as a reflective prism sheet) that changes the optical path of the light beam emitted from the second condensing optical system.

The optical shaping means includes a light shaping rod that totally reflects the light incident from the incident side end surface inside the rod and emits the light from the exit side end surface.

In the apparatus of Patent Document 1, the optical axis direction of the first condensing optical system (lens system) is the z-axis direction, and the thickness direction of the reflective prism sheet is the y-axis direction perpendicular to the z-axis. The direction perpendicular to the direction and the y-axis direction is defined as the x-axis direction.

Japanese Patent No. 5830828

According to the apparatus of Patent Document 1, by improving the light utilization efficiency, the power consumption of the LED as a light emitting source can be minimized to reduce the power consumption. However, in the apparatus of Patent Document 1, light that cannot be taken into the rod is generated at the incident surface of the optical shaping rod, which lowers the light utilization efficiency.

Further, the apparatus of Patent Document 1 has a configuration in which a lens system having a focal length f1 is on the object side and a reflection mirror system having a focal length f2 (f2> f1) is on the image side to form a bilateral telecentric optical system, for example. When the mutual distance between the lens system and the reflection mirror system is widened for application to a large screen exceeding 100 inches, it is necessary to increase the y-direction dimension of the reflection mirror system in order to uniformly illuminate the entire screen. Inevitably, it was found that the size of the backlight device in the thickness direction had to be increased, and therefore it was difficult to reduce the thickness of the device when applying it to a large screen.

Further, the device of Patent Document 1 can be applied to lighting type signboards, lighting for posters and paintings, general lighting with uniform surface brightness, etc., but when the surface to be illuminated has a large area, the area is large. For the same reason as described above, it is difficult to reduce the thickness of the device when applying the above to the illuminated surface.

The present invention has been made in view of the above circumstances, and an object of the present invention is to further improve the light utilization efficiency by using a synthetic lens system composed of a toroidal lens instead of the shaping rod. , The power consumption of the light source can be minimized to reduce the power consumption, and a large-screen liquid crystal display, or a lighting type signboard with a large observation target surface, lighting for posters and paintings, and It is an object of the present invention to provide a lighting device capable of easily achieving a thinning of the device when applying the uniform surface brightness to general lighting.

In order to solve the above-mentioned problems and achieve the above-mentioned object, the lighting apparatus according to the present invention has the following gist structure.
[1] In a lighting device including a surface light source, a synthetic lens system, a reflection mirror, and a reflection prism sheet.
The synthetic lens system is composed of three dimensions of x-axis, y-axis, and z-axis that are orthogonal to each other.
The optical axis of the synthetic lens system is provided on the z-axis.
A first toroidal lens that captures the luminous flux emitted from the surface light source from the concave incident surface and emits it from the toroidal surface-shaped exit surface whose radius of curvature in the x direction is larger than the radius of curvature in the y direction.
It comprises a second toroidal lens that takes in the light flux emitted from the first toroidal lens from the incident surface and emits it from an emitting surface having a toroidal surface shape in which the radius of curvature in the x direction is larger than the radius of curvature in the y direction.
It has a front focal point Fyz in the yz plane and a front focal point Fxz in the x-z plane in order from the side closer to the first toroidal lens, and the front focal point Fxz and the incident surface of the first toroidal lens. The position of the surface light source is set between and near the front focal point Fyz.
The illumination optical system including the surface light source and the synthetic lens system has a rectangular illumination area on the xy plane on the emission side of the synthetic lens system.
Moreover,
The reflection mirror has a focal length f ₂ , and a means for reflecting a light flux emitted from the second toroidal lens in a direction inclined with the z-axis, with the distance from the second toroidal lens being approximately f _2. Have and
The reflecting prism sheet is a lighting device having a means for changing an optical path of a light flux reflected from the reflecting mirror.
[2] In [1], the normal projection of the emission surface of the surface light source and the incident surface of the first toroidal lens on the xy plane is projected in the x-direction and the y-direction in the long-side direction and the short-side direction, respectively. A lighting device characterized by having a rectangular shape.
[3] The lighting device according to [1] or [2], characterized in that a plurality of the illumination optical systems are provided.
[4] In any one of [1] to [3], the lighting device is characterized in that the lighting device is a liquid crystal backlight device.

According to the present invention, the light utilization efficiency can be further improved by utilizing the toroidal lens, the power consumption of the light source can be minimized, the power consumption can be reduced, and a large-screen liquid crystal display or a large screen liquid crystal display or. It has an excellent effect that the device can be easily made thinner when it is applied to a lighting type signboard having a large observation target surface, lighting for posters and paintings, and general lighting having uniform surface brightness.

It is a schematic diagram which shows an example of embodiment of this invention. It is a schematic diagram which shows the rectangular lighting area. It is a schematic diagram which shows an example of the Embodiment which provided a plurality of illumination optical systems. It is a ray tracing diagram by the optical simulation of Example 1. FIG. It is a 2D intensity diagram of the illumination area (illumination distance = 273mm) immediately before the reflection mirror by the optical simulation of Example 1. FIG. It is a two-dimensional intensity figure of the secondary reflection light flux from the reflection prism sheet by the optical simulation of Example 1. FIG. It is a two-dimensional intensity diagram of the light irradiated to the illumination area (illumination distance = 1 m) by the optical simulation of Example 2. FIG. It is a two-dimensional intensity diagram of the light irradiated to the illumination area (illumination distance = 10m) by the optical simulation of Example 2. FIG. It is a two-dimensional intensity diagram of the light irradiated to the illumination area (illumination distance = 100m) by the optical simulation of Example 2. FIG. It is a two-dimensional intensity diagram of the light irradiated to the illumination area (illumination distance = 1 m) by the optical simulation of Example 2. FIG. It is a schematic diagram for demonstrating the difference in the main ray direction of the image light emitted from the parallel light backlight apparatus (b)-(d), and the existing backlight apparatus (a).

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments. Further, in each drawing, the same or corresponding elements are appropriately designated by the same reference numerals, and duplicate description will be omitted as appropriate. Furthermore, it should be noted that the drawings are schematic and the dimensional relationships of each element may differ from the actual ones. Even between the drawings, there may be parts where the relationship and ratio of the dimensions are different from each other.

1A and 1B schematically show an example of an embodiment of the present invention, where FIG. 1A is a cross-sectional view taken along the line yz and FIG. 1B is a cross-sectional view taken along the line xz.

The lighting device of FIG. 1 includes a surface light source 1, a synthetic lens system 5, a reflection mirror 8, and a reflection prism sheet 9.

The surface light source 1 is adopted because it is easier to form an illumination area described later than a point light source or a line light source, and is made of, for example, an LED chip.

The synthetic lens system 5 is composed of three dimensions of an x-axis, a y-axis, and a z-axis that are orthogonal to each other, and has an optical axis of the synthetic lens system 2 on the z-axis.

In addition to the above, the synthetic lens system 5 takes in the luminous flux emitted from the surface light source 1 from the concave incident surface and emits it from the toroidal surface-shaped exit surface from the first toroidal lens 2 and the first toroidal lens 2. The second toroidal lens 3 is provided with a second toroidal lens 3 that captures the emitted light flux from the incident surface and emits it from the toroidal surface-shaped emission surface.

The radius of curvature of the toroidal surface of each of the first toroidal lens 2 and the second toroidal lens 3 was set to "radius of curvature in the x direction> radius of curvature in the y direction".

Therefore, the front focal Fyz in the yz plane of the synthetic lens system 5 is located closer to the first toroidal lens 2 than the front focal Fxz in the xz plane. Therefore, in the present invention, the position of the surface light source 1 is set between the front focal point Fxz and the first toroidal lens 2 and in the vicinity of the front focal point Fyz.

In FIG. 1, the synthetic lens system 5 has front principal points Myz and Mxz in the yz plane and the xz plane, respectively, and is the distance from the front principal point Myz to the front focal point Fyz. It has a focal point fyz in the −z plane and a focal point fxz in the x—z plane, which is the distance from the anterior principal point Mxz to the anterior focal point Fxz.

Here, the vicinity of the front focal point Fyz means a region centered on the front focal point Fyz, within a circle having a radius of 20% of fyz, and on the z-axis.

Further, the concave shape of the incident surface of the first toroidal lens 2 is a cylindrical inner peripheral surface shape (see FIG. 1), so that the intake rate of the light flux emitted from the surface light source 1 can be set to about 96%. Further, by making the meniscus lens surface shape (not shown), the intake rate of the light flux emitted from the surface light source 1 can be almost 100%.

The shape of the incident surface of the second toroidal lens 3 may be a planar shape (see FIG. 1) or a concave shape (not shown).

As described above, the composite lens 5 has a front focal length Fyz closer to the first toroidal lens 2 than the anterior focal length Fxz, and is between the anterior focal length Fxz and the first toroidal lens 2 and in the vicinity of the anterior focal length Fyz. In the set of the surface light source 1 and the synthetic lens system 5 (hereinafter, also referred to as the illumination optical system 7), the spread of the luminous flux on the emission side becomes small in the yz plane. On the other hand, a luminous flux approaching the parallel luminous flux is obtained, while a luminous flux having a larger spread than the luminous flux in the yz plane is obtained in the x-z plane. Therefore, as shown in FIG. 2, the illumination optical system 7 has a rectangular illumination area having the x direction as the long side direction and the y direction as the short side direction on the xy plane on the emission side of the synthetic lens system 5. Have. Here, the illumination area is an area that can be distinguished from the background by the naked eye of the viewer. This region is determined by the difference in illuminance.

FIG. 2 shows the definition of the rectangular shape ratio of the figure. That is,
Rectangle ratio of figure = (area of figure / area of rectangle circumscribing figure) x 100 (%)
And said. In this definition, "circumscribed rectangle" means the smallest rectangle among the circumscribed rectangles. Then, when the rectangular shape ratio when the figure is the illuminated area (that is, the rectangular shape ratio of the illuminated area) is larger than that when the figure is an elliptical shape (that is, the rectangular shape ratio of the elliptical shape = 78%). The lighting area is called a "rectangular lighting area".

Within this rectangular illumination area, the variation in illuminance is within ± 40% of the median, and uniform brightness can be obtained. However, when the surface light source 1 deviates from the vicinity of the front focal point Fyz, it becomes difficult to obtain a rectangular illumination area.

The ratio of the long side to the short side of the rectangular illumination area can be set by the ratio of the radius of curvature in the y direction and the x direction of the toroidal surface of the synthetic lens system 5. The distance in the z direction on the emission side starting from the surface light source 1 is also referred to as an illumination distance.

Further, the reflection mirror 8 has a focal length f ₂ , and the distance from the second toroidal lens 3 is approximately f ₂ , and the luminous flux emitted from the second toroidal lens 3 (hereinafter, also referred to as a primary luminous flux). Has a concave reflecting surface 8A formed on the reflecting substrate 8B as a means for reflecting the lens in a direction inclined with the z-axis. Here, approximately f ₂ means that it is within f _{2 ± 20%.}

By setting the distance between the _{concave reflecting surface 8A having the focal length f 2} (hereinafter, also simply referred to as the reflecting surface 8A) and the second toroidal lens 3 to be approximately f ₂ , the optical axis of the reflecting surface 8A can be set. When on the z-axis, the primary light flux behaves as follows.

That is, in the x-z plane, the primary luminous flux is emitted from the vicinity of the focal point of the reflecting surface 8A, diffuses and is incident on the reflecting surface 8A. Since the luminous flux is incident on the reflecting surface 8A in the yz plane in a state closer to the parallel light flux than in the xz plane, the reflected light flux from the reflecting surface 8A (hereinafter, also referred to as a primary reflected light flux). Condenses near the focal point of the reflective surface 8A.

Therefore, by tilting the optical axis of the reflecting surface 8A from the z-axis (rotating clockwise by an angle θ in the yz plane in FIG. 1), the main ray of the primary reflected light beam is tilted by an angle 2θ with the z-axis. It can be inclined in the direction of the light and incident on the reflective prism sheet 9.

Further, the reflective prism sheet 9 has a plurality of prism-shaped ridges 9A formed on the sheet substrate 9B as a means for changing the optical path of the primary reflected light flux. The side surface of the prism-shaped ridge 9A is configured to reflect the primary reflected light flux to form a secondary reflected light flux. The sheet substrate 9B is installed parallel to the x-z plane (see FIG. 1), and the height, apex angle, and arrangement spacing of the reflective prism-shaped protrusion 9A are set to appropriate values according to the angle θ of the reflective surface 8A. By setting, the optical path of the secondary reflected light beam can be set as a downward optical path in the z direction.

Therefore, in the embodiment of FIG. 1, the light beam (primary light beam) emitted from the illumination optical system 7 forms a rectangular illumination area so as to overlap with the reflection surface 8A of the reflection mirror 8 to reflect the primary light beam. Reflected on the surface 8A and incident on the reflecting prism sheet 9 as a primary reflected light beam toward an oblique (upper left) direction, and reflected and incident on an illuminated surface (not shown) as a secondary reflected light beam downward in the y direction. Can be done. At this time, the loss of light at the time of conversion from the primary luminous flux to the primary reflected light flux and at the time of conversion from the primary reflected light flux to the secondary reflected light flux can be suppressed to about 5% or less, respectively. Therefore, in a normal case where the illuminated object surface has a rectangular shape, it is possible to improve the light utilization efficiency and the brightness uniformity of the illuminated object surface corresponding to a wide range of sizes and aspect ratios.

Further, in the above-described embodiment, from the viewpoint of further increasing the rectangular shape ratio (see FIG. 2) of the above-mentioned illumination area, to the xy plane between the exit surface of the surface light source 1 and the incident surface of the first toroidal lens 2. It is preferable that the normal projection of the above is a rectangular shape in which the x-direction and the y-direction are the long-side direction and the short-side direction, respectively, and this is the case in the example of FIG.

Further, in the above-described embodiment, the brightness can be increased as an embodiment including a plurality of illumination optical systems 7 including a surface light source 1 and a synthetic lens system 5. An example of this is shown in FIG. FIG. 3 is an example in which three illumination optical systems 7 are provided in the x direction. In FIG. 3, the reflection mirror and the reflection prism sheet are not shown.

According to the lighting device according to the above-described embodiment, the light utilization efficiency can be further improved by utilizing the toroidal lens, the power consumption of the light source can be minimized, the power consumption can be reduced, and the large screen can be used. The thinness of the device can be easily achieved when the device is applied to a liquid crystal display, a lighting type signboard having a large observation target surface, lighting for posters and paintings, and general lighting having uniform surface brightness.

Further, by using the lighting device according to the above-described embodiment as a liquid crystal backlight device, it is possible to obtain a liquid crystal backlight device that is thinner and has higher light utilization efficiency and brightness uniformity than the device of Patent Document 1. Can be done. For example, when a 100-inch size liquid crystal backlight device is configured with the lighting device of the present invention, the thickness of the device can be reduced by about 40% as compared with the device of Patent Document 1.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples.
[Example 1] As the first embodiment, the specifications of the lighting device in the embodiment of FIG. 1 are as follows.
(A) The surface light source 1 is made of an LED chip, and the emission surface is a rectangular plane having a width of 4 mm and a length of 1 mm. Here, the horizontal means the x direction and the vertical means the y direction (the same applies hereinafter).
(B) The first toroidal lens 2 is made of glass (S-LAH53), the xy plane figure of the lens is a rectangle of 8 mm in width × 3.2 mm in length, and the lens thickness on the optical axis is 2.3 mm. The radius of curvature of the incident surface was 10 mm in width × infinity in length, and the radius of curvature of the exit surface was 5.5 mm in width × 2 mm in length.
(C) The second toroidal lens 3 is made of glass (SK5), the xy plane figure of the lens is a rectangle of width 54 mm × length 24 mm, the lens thickness on the optical axis is 15 mm, and the curvature of the incident surface. The radius was set to infinity in width × infinity in length, and the radius of curvature of the exit surface was set to 42 mm in width × 21 mm in length.
(D) The distance between the first and second toroidal lenses 2 and 3 was set to 17.3 mm on the optical axis.
(E) The positions of the front focal points Fyz and Fxz of the synthetic lens system 5 are positions such that Fyz is 0.656 mm and Fxz is 7.368 mm on the front side from the incident surface of the first toroidal lens 2 in paraxial theory. Therefore, the position of the exit surface of the surface light source 1 is set to 0.4 mm.
(F) In the reflection mirror 8, the focal length f ₂ of the reflection surface 8A is 238 mm, the distance from the second toroidal lens 3 is f ₂ (= 238 mm), the x-direction size is 230 mm, and the y-direction size is 30 mm (however). , When the tilt angle θ was 0 ° before tilting), and the tilt angle θ was set to about 3 °.

At this time, the illumination distance from the surface light source 1 to the position of the reflecting surface 8A is about 273 mm.
(G) In the reflective prism sheet 9, the surface of the sheet substrate 9B on the prism-shaped ridge 9A side is parallel to the x-z plane, and is 9.5 mm above the z-axis with the second toroidal lens 3 and the reflective mirror. The height of the prism-shaped ridge 9A is arranged so as to cover the space between the lens 8 and the prism-shaped ridge 9A so that the primary reflected light beam from diagonally lower right is reflected and becomes the secondary reflected light beam traveling in the downward optical path in the z-axis direction. Now, the apex angle and the arrangement spacing are designed.

An optical simulation was performed on the lighting device of Example 1. FIG. 4 is a light ray tracking diagram by optical simulation of Example 1, FIG. 5 is a two-dimensional intensity diagram of an illumination area (illumination distance = 273 mm) immediately before a reflection mirror, and FIG. 6 is a two-dimensional intensity diagram of a secondary reflected light flux. be. The two-dimensional intensity of the secondary reflected light beam in FIG. 6 is 14.5 mm directly below the sheet substrate surface of the reflecting prism sheet 9.

According to the ray output data of the optical simulations of FIGS. 4 and 5, the light utilization efficiency of the illumination area immediately before the reflection mirror was about 96%.

In FIG. 5, the illumination area immediately before the reflection mirror has a rectangular shape (long side about 200 mm × short side about 24 mm, rectangular shape ratio about 99%), and the variation in illuminance is according to the incoherent irradiance in the optical simulation. It was about 0.01 to about 0.02 W / cm ² (about 0.015 W / cm ² ± 33%), which was within ± 40%, and the brightness was uniform. If the incoherent irradiance of the light spot in the black background is about 5 × 10 ^-8 W / cm ² or more, the light spot can be visually recognized.

In FIGS. 5, 6 and 7 to 10 described later, the “illuminance” refers to incoherent irradiance (light energy distribution).

Further, in FIG. 6, the illumination area of the secondary reflected light beam is rectangular (long side about 238 mm × short side about 200 mm, rectangular shape ratio about 96%), and the illuminance is about 1.0 × 10 ^-3 to about. The brightness was uniform at 1.8 × 10 ^-3 W / cm ² (about 1.4 × 10 ^-3 W / cm ² ± 29%).
[Example 2] As the second embodiment, in order to investigate the dependence of the shape and brightness of the illumination area of the illumination optical system 7 only on the illumination distance, the specifications of the illumination optical system 7 are used in the embodiment of FIG. The same as in Example 1, the shape and brightness of the illumination area were obtained by optical simulation when the illumination distances were 1 m, 10 m, and 100 m. The results are shown in FIGS. 7 to 9, respectively.

In FIG. 7 (illumination distance = 1 m), the illumination area has a rectangular shape (long side of about 890 mm × short side of about 140 mm, rectangular shape ratio of about 98%), and the illuminance is about 4.0 × 10 ^-4 to about 8. The brightness was uniform to be .2 × 10 ^-4 W / cm ² (about 6.1 × 10 ^-4 W / cm ^{2 ± 34%).}

In FIG. 8 (illumination distance = 10 m), the illumination area has a rectangular shape (long side about 6.0 m × short side about 1.3 m, rectangular shape ratio about 96%), and the illuminance is about 4.4 × 10 ^{−. The} brightness was uniform, ranging from 6 to about 9.8 × 10 ^-6 W / cm ² (about 7.1 × 10 ^-6 W / cm ^{2 ± 38%).}

In FIG. 9 (illumination distance = 100 m), the illumination area has a rectangular shape (long side about 88 m × short side about 12 m, rectangular shape ratio about 93%), and the illuminance is about 6.5 × 10 ^-8 to about 9. The brightness was uniform at 0.9 × 10 ^-8 W / cm ² (about 8.2 × 10 ^-8 W / cm ² ± 21%).

As described above, the illumination optical system 7 makes a rectangular illumination area having uniform brightness appear even if the illumination distance is increased. Therefore, by applying the illumination optical system 7 to the headlights of vehicles such as automobiles and trains, obstacles in front can be found faster and more reliably at night, which improves driving safety. Can contribute.
[Example 3] Example 3, in Example 1, change the lighting distance 1 m, the reflection mirror 8, the focal length f ₂ of the reflecting surface 8A 965 mm, the distance between the second toroidal lens 3 f ₂ (= 965 mm), the x-direction size was changed to 890 mm, the y-direction size was changed to 150 mm (however, when the tilt angle θ was 0 ° before tilting), and the tilt angle θ was changed to about 4 °. Further, regarding the reflective prism sheet 9, the distance above the z-axis was changed to 75 mm.

As a result of investigating the shape and brightness of the illumination area of the secondary reflected light flux at the position 75 mm directly below the z-axis by the optical simulation of the lighting device of the third embodiment, the shape is rectangular (long side about 965 mm × short side). (Approximately 890 mm, rectangularity ratio of approximately 96%), the brightness was uniform at a level of about 1/10 of that immediately before the reflection mirror 8 (FIG. 7) (however, not shown).
[Example 4] As a fourth embodiment, in the embodiment of FIG. 3 (a mode in which three illumination optical systems 7 are used), the specifications of the illumination optical system 7 are the same as those of the first embodiment, and the illumination distance is 1 m. The shape and brightness of the lighting area of the above were obtained by optical simulation. The results are shown in FIG. In this optical simulation, the reflection mirror 8 and the reflection prism sheet 9 were ignored.

In FIG. 10 (illumination distance = 1 m), the illumination area has a rectangular shape (long side about 890 mm × short side about 180 mm, rectangular shape ratio about 94%), and the illuminance is about 1.1 × 10 ^-3 to about 2. The brightness was uniform at .5 × 10 ^-3 W / cm ² (about 1.8 × 10 ^-3 W / cm ² ± 39%).

That is, when three illumination optical systems 7 are used (FIG. 10), the brightness of the illumination area at an illumination distance of 1 m is about three times as high as that when one is used (FIG. 7).
[Example 5] As the fifth embodiment, in the fourth embodiment, the focal length f ₂ of the reflecting surface 8A is 965 mm, the distance from the second toroidal lens 3 is f ₂ (= 965 mm), and the size in the x direction. 890 mm, the y-direction size was 190 mm (however, when the tilt angle θ was 0 ° before tilting), and the tilt angle θ was about 5 °. Further, the distance above the reflective prism sheet 9 from the z-axis was set to 95 mm.

As a result of investigating the shape and brightness of the illumination area of the secondary reflected light flux at the position 95 mm directly below the z-axis by the optical simulation of the lighting apparatus of Example 5, the shape is rectangular (long side about 965 mm × short side). (Approximately 890 mm, rectangularity ratio of approximately 96%), the brightness was uniform at a level of about 1/10 of that immediately before the reflection mirror 8 (FIG. 10) (however, not shown).

1 Surface light source 2 First toroidal lens 3 Second toroidal lens 5 Synthetic lens system 7 Illumination optical system 8 Reflective mirror 8A Concave reflective surface 8B Reflective substrate 9 Reflective prism sheet 9A Reflective prism-shaped ridge 9B Sheet substrate

Claims (4)

In a lighting device consisting of a surface light source, a synthetic lens system, a reflection mirror, and a reflection prism sheet.
The synthetic lens system is composed of three dimensions of x-axis, y-axis, and z-axis that are orthogonal to each other.
The optical axis of the synthetic lens system is provided on the z-axis.
A first toroidal lens that captures the luminous flux emitted from the surface light source from the concave incident surface and emits it from the toroidal surface-shaped exit surface whose radius of curvature in the x direction is larger than the radius of curvature in the y direction.
A second toroidal lens that takes in the luminous flux emitted from the first toroidal lens from the incident surface and emits it from an emitting surface having a toroidal surface shape in which the radius of curvature in the x direction is larger than the radius of curvature in the y direction is provided.
It has a front focal point Fyz in the yz plane and a front focal point Fxz in the x-z plane in order from the side closer to the first toroidal lens, and the front focal point Fxz and the incident surface of the first toroidal lens. The position of the surface light source is set between and near the front focal point Fyz.
The illumination optical system including the surface light source and the synthetic lens system has a rectangular illumination area on the xy plane on the emission side of the synthetic lens system.
Moreover,
The reflection mirror has a focal length f ₂ , and a means for reflecting a light flux emitted from the second toroidal lens in a direction inclined with the z-axis, with the distance from the second toroidal lens being approximately f _2. Have and
The reflecting prism sheet is a lighting device having a means for changing an optical path of a light flux reflected from the reflecting mirror. The normal projection of the emission surface of the surface light source and the incident surface of the first toroidal lens on the xy plane is formed into a rectangular shape in which the x direction and the y direction are the long side direction and the short side direction, respectively. The lighting device according to claim 1. The lighting device according to claim 1 or 2, wherein a plurality of the illumination optical systems are provided. The lighting device according to any one of claims 1 to 3, wherein the lighting device is a backlight device for a liquid crystal display.

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