Surface light source illumination device and method for manufacturing surface light source illumination device

Abstract

To provide a surface light source illumination device that can irradiate an object with a sufficient amount of observation light while suppressing increase in inhibition light that directly exits from a prism plane.SOLUTION: For a plurality of first prisms 32a, 32b provided in a surface light source illumination device, equations 35≤α≤65, H / h≤0.2 are satisfied when an average angle formed by inclined surfaces 132a, 133a and a light emission surface 33 is α, a depth of the first prisms 32a, 32b is H, a width of a prism opening is D, and a distance to an intersection point C when a second virtual line having a point A as a starting point is drawn so that an angle formed by a first virtual line connecting the point A and a point B of the prism opening is the same as the average angle α of the first prisms 32a, 32b, a point E located on a side of a light emission plane 33 with respect to bottom surfaces 132b, 133b on the second virtual line is at a position where a third virtual line connected to the point E with the point B as a starting point and the second virtual line are perpendicular, and a perpendicular line is drawn to the first virtual line from the point E, is h.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a surface light source illumination device and a method for manufacturing the surface light source illumination device, and more particularly to a surface light source illumination device using a light guide plate and a method for manufacturing the surface light source illumination device. [Background technology]

[0002] In recent years, illumination devices that emit light for purposes such as visual inspection of products have become known. For example, Patent Document 1 discloses an illumination device that includes a first light guide plate having LEDs that emit light from at least two directions, a first surface that emits light incident from the LEDs, and a second surface that faces the first surface and has a plurality of prisms arranged thereon that reflect and / or refract the light. As a result, light that enters the first light guide plate is reflected by the second surface and emitted to the outside from the other, first surface, to illuminate a predetermined object, and the object can be observed through the light guide plate from the second surface side of the light guide plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-95239 Summary of the Invention [Problem to be solved by the invention]

[0004] When inspecting the appearance of an object, for example, a light source is disposed on an end face of a light guide plate, the object is disposed on the first surface side of the light guide plate, and an imaging device or an observer for observing the object is disposed on the second surface side of the light guide plate. In this case, since a prism or the like is formed on the second surface side of the light guide plate, light emitted from the light source is reflected by the prism formed on the light guide plate toward the first surface side and is irradiated onto the object from the first surface. The observation light irradiated onto the object is reflected by the object and passes through the light guide plate, allowing the imaging device or the observer to recognize the object.

[0005] In such a configuration, some of the light emitted from the light source may be emitted from the second surface by the prism and may directly enter the image capture device or the observer. The light that directly enters the image capture device or the observer's eyes becomes interference light. If the amount of interference light increases, the accuracy of the appearance inspection decreases.

[0006] Furthermore, if the amount of inhibiting light increases, the signal-to-noise ratio, which is the ratio between the inhibiting light directly emitted from the second surface and the controlled observation light emitted from the first surface, decreases, resulting in a decrease in the illumination rate for the object.

[0007] Therefore, the present disclosure provides a surface light source illumination device and the like that can irradiate an object with a sufficient amount of observation light while suppressing an increase in the interfering light that is directly emitted from the prism surface. [Means for solving the problem]

[0008] A surface light source illumination device according to one aspect of the present disclosure includes a light source; a first light guide plate having a light incident end surface into which light emitted from the light source is introduced, a light exit surface that outputs the introduced light, and a first prism surface that faces the light exit surface and has a plurality of first prisms that reflect and / or refract light formed thereon, wherein the plurality of first prisms are recesses having an inclined surface that reflects and / or refracts the light introduced from the light source and a bottom surface that is approximately parallel to the first prism surface, and in a cross section when the plurality of first prisms are cut along a plane perpendicular to the first prism surface, where H is the depth of the first prism, D is the width of the prism opening, a second imaginary line is drawn starting from point A so that the angle formed with a first imaginary line connecting point A, which is one of the two ends of the prism opening, and point B, which is the other end, is the same as the average angle α of the first prism, and point E, which is on the second imaginary line closer to the light exit surface than the bottom surface of the first prism, is at a position where a third imaginary line connecting point E with point B as the starting point, and the second imaginary line are perpendicular to each other, and h is the distance from point E to point C when a perpendicular line is drawn from point E to the first imaginary line, 35 ≦ α ≦ 65 H / h ≦0.2

number

[0009] Furthermore, a method for manufacturing a surface light source illumination device according to one embodiment of the present disclosure is a method for manufacturing a surface light source illumination device including a first light guide plate having a first prism surface on which a plurality of first concave prisms are formed, and a second light guide plate having a second prism surface on which a plurality of second convex prisms are formed, wherein the first light guide plate and the second light guide plate are manufactured using stampers made from the same master. [Effects of the Invention]

[0010] According to the surface light source illumination device and the like of the present disclosure, it is possible to irradiate an object with a sufficient amount of observation light while suppressing an increase in the interfering light that is directly emitted from the prism surface.

[0011] Further advantages and effects of one aspect of the present disclosure will become apparent from the specification and drawings. Such advantages and / or effects are provided by some embodiments and features described in the specification and drawings, but not all of them necessarily need to be provided to obtain one or more identical features. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view of a surface light source illumination device according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the surface light source illuminating device taken along the line AA in FIG. [Figure 3] FIG. 3 is a cross-sectional view of the first light guide plate for explaining the first prism. [Figure 4] FIG. 4 is a diagram showing the relationship between the luminous flux ratio of effective light and the average angle of the first prism. [Figure 5] FIG. 5 is a diagram showing the relationship between the luminous flux ratio of the inhibiting light and H / h. [Figure 6] FIG. 6 is a cross-sectional view showing the first prism for explaining (Equation 1). [Figure 7A]FIG. 7A is a cross-sectional view of a surface light source illuminating device having a first light guide plate and a second light guide plate. [Figure 7B] FIG. 7B is a cross-sectional view of the first light guide plate and the second light guide plate for explaining the first prism and the second prism. [Figure 8] FIG. 8 is a diagram showing the light distribution of a surface light source illuminating device having a first light guide plate and a second light guide plate. [Figure 9] FIG. 9 is a diagram illustrating a method for producing the first light guide plate and the second light guide plate. [Figure 10] FIG. 10 is a diagram illustrating the inhibiting light emitted from the first prism of the light guide plate of the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0014] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in the independent claims are described as optional components.

[0015] In addition, each drawing is a schematic diagram and is not necessarily an exact illustration. In addition, the same components are denoted by the same reference numerals in each drawing.

[0016] 1, a predetermined direction parallel to the first prism surface and the light exit surface along which the flat surface light source illumination device extends is defined as the X-axis positive direction, a direction perpendicular to the X-axis positive direction is defined as the Y-axis positive direction, and a direction perpendicular to the X-axis positive direction and the Y-axis positive direction is defined as the thickness direction of the flat surface light source illumination device, and the imaging device side with respect to the surface light source illumination device is defined as the Z-axis positive direction. The directions in FIG. 1 may also be applied to FIG. 2 and subsequent figures.

[0017] Furthermore, in the following embodiments, expressions such as trapezoid, Z-axis direction, and approximately rectangular are used. For example, trapezoid, Z-axis direction, and approximately rectangular do not only mean a perfect trapezoid, Z-axis direction, and rectangle, but also mean a substantial trapezoid, Z-axis direction, and rectangle, i.e., with an error of a few percent. Furthermore, trapezoid, Z-axis direction, and approximately rectangular mean a trapezoid, Z-axis direction, and rectangle within the scope in which the effects of the present disclosure can be achieved. The same applies to other expressions using "shape," "direction," and "approximately."

[0018] (Embodiment) <Configuration> Hereinafter, a surface light source illuminating device 3 according to an embodiment will be described with reference to FIGS.

[0019] FIG. 1 is a perspective view of a surface light source illumination device 3 according to an embodiment. FIG. 2 is a cross-sectional view of the surface light source illumination device 3 taken along line AA in FIG. 1. FIG. 3 is a cross-sectional view of first light guide plates 30, 30a for illustrating first prisms 32a, 32b. FIG. 3(a) shows a case where the cross section of first prism 32a, when the first light guide plate 30 is cut at first prism surface 32, has a trapezoidal shape that tapers from the first prism surface 32 toward the light exit surface 33. FIG. 3(b) shows a case where the cross section of first prism 32b, when the first light guide plate 30a is cut at first prism surface 32, has an inclined surface 133a of first prism surface 32 that is a concave curve (e.g., a part of a spherical surface).

[0020] As shown in FIG. 1 , a surface light source illumination device 3 according to an embodiment is used for visual inspection and is mounted on a visual inspection system 1. The visual inspection system 1 can perform visual inspection of an object. The object to be observed is disposed facing the light exit surface 33 of the first light guide plate 30, and the imaging device 5 or an observer is disposed facing the first prism surface 32 of the first light guide plate 30. In this case, when light emitted from the light exit surface 33 of the first light guide plate 30 illuminates the object, observation light, which is light irradiated onto the object, is reflected by the object and passes through the first light guide plate 30, allowing the imaging device 5 or observer to recognize the object via the first light guide plate 30. The observation light is light irradiated onto the object, reflected by the object, passes through the first light guide plate 30, and is observed by the imaging device 5 or observer.

[0021] The visual inspection system 1 of this embodiment includes a surface light source illumination device 3, an imaging device 5, and an image analysis device.

[0022] The surface light source illuminating device 3 is a light guide plate illuminating fixture using a first light guide plate 30.

[0023] As shown in FIGS. 1 and 2, the surface light source luminaire 3 includes a first light guide plate 30, a light source module 20, and a housing .

[0024] The light source module 20 is disposed so as to face a light incident end surface 31 which is an end surface of the first light guide plate 30 , and can cause emitted light to be incident on the light incident end surface 31 of the first light guide plate 30 .

[0025] The light source module 20 has a substrate 22 and a plurality of light sources 21. The substrate 22 has a generally rectangular plate shape that is elongated along the Z-axis direction. The substrate 22 is formed of, for example, a ceramic substrate, a resin substrate, or a metal-based substrate. Electrode terminals and metal wiring in a predetermined pattern are formed on the substrate 22. The electrode terminals are provided to receive DC power from a power supply device for causing the plurality of light sources 21 to emit light. The power supply device will not be described in detail, but for example, converts AC power from a commercial power source into DC power, and steps down the voltage to an appropriate voltage before supplying it to the light source module 20. The metal wiring in the predetermined pattern is provided to electrically connect the plurality of light sources 21.

[0026] The plurality of light sources 21 are mounted on the mounting surface of the substrate 22 at predetermined intervals along the longitudinal direction of the substrate 22. Each of the plurality of light sources 21 is, for example, an LED (Light Emitting Diode) module.

[0027] Each of the plurality of light sources 21 has a light-emitting element, which is an LED chip, and a phosphor that emits fluorescence by wavelength-converting the light emitted by the light-emitting element. The light-emitting element is an LED chip placed in a cavity molded from resin, and emits light that becomes the emitted light of the surface light source illumination device 3. The light-emitting element is sealed in the cavity by a sealing member that contains a phosphor. For example, if the light-emitting element is a blue LED chip that emits blue light, the sealing member is made of a phosphor-containing resin in which phosphor particles are dispersed in a silicone resin, and the phosphor particles are made of, for example, a YAG-based yellow phosphor.

[0028] The first light guide plate 30 is a light-transmitting member that receives light emitted from the light source 21 and emits the incident light as illumination light. The first light guide plate 30 is made of a light-transmitting material such as acrylic resin or glass.

[0029] The first light guide plate 30 has a flat plate shape. In this embodiment, the first light guide plate 30 has a rectangular shape in a plan view. The shape of the first light guide plate 30 may be a circle or another polygonal shape. The shape of the first light guide plate 30 may also be another known shape and is not limited to this embodiment.

[0030] The first light guide plate 30 has a light incident end surface 31 , a first prism surface 32 , and a light exit surface 33 .

[0031] The light incident end surface 31 is a surface facing the light emitting surface of the light source 21. Light emitted by the light source 21 is introduced into the light incident end surface 31. The specific arrangement of the light source 21 relative to the light incident end surface 31 will be described later.

[0032] The first prism surface 32 is a surface that is parallel to the light exit surface 33 and perpendicular to the light incident end surface 31. The first prism surface 32 is the surface opposite the light exit surface 33. The first prism surface 32 has a plurality of first prisms 32a formed thereon that reflect and / or refract the light introduced from the light incident end surface 31 toward the light exit surface 33.

[0033] The multiple first prisms 32a are arranged two-dimensionally on the first prism surface 32 of the first light guide plate 30. That is, the multiple first prisms 32a are arranged along the X-axis direction, and also along the Y-axis direction that is perpendicular to the X-axis direction.

[0034] In this embodiment, the coverage of the multiple first prisms 32a formed on the first prism surface 32 is 20% or more and 50% or less. The coverage of the first prisms 32a is calculated as the total area of ​​all the first prisms 32a on the first prism surface 32 of the first light guide plate 30. The coverage can also be considered as the density of the first prisms 32a. If the coverage is higher than 50%, the light extraction efficiency from the first light guide plate 30 improves, but the transparency of the first light guide plate 30 decreases, making it difficult for the imaging device 5 or the observer to recognize the object through the first light guide plate 30. On the other hand, if the coverage is less than 20%, the light extraction efficiency from the first light guide plate 30 decreases, and an insufficient amount of light is irradiated onto the object, making it difficult for the imaging device 5 or the observer to recognize the object through the first light guide plate 30. For this reason, the coverage of the plurality of first prisms 32a is set to 20% or more and 50% or less so that the imaging device 5 or the observer can recognize the object while obtaining the desired light extraction efficiency. In this case, the imaging device 5 and the observer can irradiate the object with light from the light emitting surface 33, so that they can see the object and recognize the object irradiated with light through the first light guide plate 30. The specific configuration of the first prisms 32a will be described later.

[0035] An anti-reflection coating, anti-reflection film, or anti-reflection plate may be laminated on first prism surface 32. The anti-reflection coating, anti-reflection film, or anti-reflection plate is made of a material that has a reflectance equal to or lower than a predetermined value for return light reflected and / or scattered by an object. In this case, it is possible to prevent external light from being reflected by first prism surface 32 and becoming interfering light that is irradiated onto image capture device 5 or the observer.

[0036] The light exit surface 33 is a surface disposed on the opposite side to the first prism surface 32. The light exit surface 33 outputs the light introduced from the light incident end surface 31, that is, the light reflected by the first prism surface 32.

[0037] An anti-reflection coating or anti-reflection film may be laminated on the light exit surface 33. The anti-reflection coating or anti-reflection film is made of a material that has a reflectance equal to or lower than a predetermined value with respect to return light reflected and / or scattered by an object. In this case, it is possible to prevent a portion of the light that is reflected and / or refracted by the first prism 32a and transmitted through the light exit surface 33 from being further reflected by the light exit surface 33 and becoming interfering light that interferes with the imaging device 5 or the observer.

[0038] The housing 10 is a frame having a first opening 11 and a second opening 12 facing the first opening 11. The housing 10 is disposed along the edge portion of the first light guide plate 30 and is capable of supporting the edge portion of the first light guide plate 30 and the light source module 20. The housing 10 supports the first light guide plate 30 so that the first prism surface 32 is exposed from the first opening 11 and the light exit surface 33 of the first light guide plate 30 is exposed from the second opening 12.

[0039] In this case, the imaging device 5 or the observer is positioned facing the first opening 11, and the object is positioned facing the second opening 12. Light emitted from the light exit surface 33 and passing through the first opening 11 is reflected by the object, passes through the first light guide plate 30, and passes through the second opening 12 to be incident on the imaging device 5 or the observer. This allows the imaging device 5 or the observer to recognize the object.

[0040] In this embodiment, since the first light guide plate 30 has a rectangular shape, the housing 10 is a rectangular frame body arranged along the edge portion of the rectangular first light guide plate 30. Groove portions 15 capable of sandwiching and supporting the first light guide plate 30 are formed on the inner peripheral surface side of the housing 10 (the inner peripheral surface side of the frame body). The groove portions 15 have a first groove edge portion 15a that is along the edge portion of the first prism surface 32 of the first light guide plate 30, and a second groove edge portion 15b that faces the first groove edge portion 15a and is along the edge portion of the light exit surface 33 of the first light guide plate 30. When the edge portion of the first light guide plate 30 is fitted into and connected to the groove portion 15, the first groove edge portion 15a and the second groove edge portion 15b of the housing 10 can support the first light guide plate 30 so as to sandwich the first prism surface 32 and the light exit surface 33 at the edge portion of the first light guide plate 30.

[0041] When the housing 10 supports the first light guide plate 30, a gap for arranging the light source module 20 is formed between the end face of the first light guide plate 30 and the bottom face of the groove 15. Therefore, the light source module 20 is arranged at the bottom of the groove 15. The groove 15 of the housing 10 can support the light source module 20. In other words, the groove 15 of the housing 10 supports and accommodates the light source module 20 so that light is introduced to the end face of the first light guide plate 30. Therefore, when each of the multiple light sources 21 in the light source module 20 emits light, the light can enter from the end face of the first light guide plate 30.

[0042] The inner surface of the housing 10 may be subjected to a surface treatment of a black material or a light-absorbing surface treatment. This can absorb leak light, stray light, etc. from the light source 21, and can prevent the leak light from interfering with the imaging device 5 or the observer.

[0043] The imaging device 5 captures an image of an object illuminated with illumination light from the surface light source illumination device 3, and acquires the image. The imaging device 5 has a lens and an imaging element (neither of which are shown). The imaging element is a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor.

[0044] The image analysis device includes an image processing unit, a storage unit, a display unit, etc. The image processing unit is a CPU and / or a GPU (Graphics Processing Unit). The image processing unit is configured to receive an image acquired by the imaging device 5 as an electrical signal (hereinafter also referred to as an image signal) and perform various signal processing on the image signal, such as noise removal processing and edge enhancement processing. These signal processing functions are realized by the CPU and / or GPU executing predetermined sequences, etc.

[0045] The storage unit is configured with a storage device such as a RAM (Random Access Memory), an SSD (Solid State Device), or an HDD (Hard Disk Drive), etc. The storage unit can store image signals before and after signal processing.

[0046] The display unit is a display device such as a liquid crystal display, an organic EL (Electro-Luminescence) display, etc. The display unit displays the image of the object after signal processing by the image processing unit.

[0047] Next, the specific arrangement of the light source 21 relative to the light incident end surface 31 in this embodiment will be described in detail.

[0048] Each of the plurality of first prisms 32a has a frustum shape. In this embodiment, each of the plurality of first prisms 32a has a frustum shape of a circular cone or a truncated pyramid. When the first light guide plate 30 is cut at the first prism surface 32, the cross section of the first prism 32a has a trapezoidal recess that tapers from the first prism surface 32 toward the light exit surface 33.

[0049] When each of the plurality of first prisms 32a has a truncated cone shape, the plurality of first prisms 32a has a circular shape in a plan view. In this case, the plurality of light sources 21 may be arranged so that light is introduced into the first light guide plate 30 from at least two directions. That is, one or more first light sources of the plurality of light sources 21 may be arranged to face a first light incident end face of the plurality of light incident end faces 31, and one or more second light sources of the plurality of light sources 21 may be arranged to face a second light incident end face of the plurality of light incident end faces 31.

[0050] When each of the plurality of first prisms 32a has a truncated pyramidal shape, the plurality of first prisms 32a have a polygonal shape in a planar view. In this embodiment, the plurality of first prisms 32a have a rectangular shape in a planar view. In this case, the plurality of light sources 21 may be arranged to introduce light into the first light guide plate 30 from two or four directions. That is, one or more first light sources of the plurality of light sources 21 may be arranged to face a first light-entering end face of the plurality of light-entering end faces 31, one or more second light sources of the plurality of light sources 21 may be arranged to face a second light-entering end face of the plurality of light-entering end faces 31, one or more third light sources of the plurality of light sources 21 may be arranged to face a third light-entering end face of the plurality of light-entering end faces 31, and one or more fourth light sources of the plurality of light sources 21 may be arranged to face a fourth light-entering end face of the plurality of light-entering end faces 31. FIG. 1 illustrates an example in which the plurality of light sources 21 are arranged so as to introduce light into the first light guide plate 30 from four directions.

[0051] Next, with reference to FIGS. 3(a), 3(b) and 4, the configuration of each of the plurality of first prisms 32a of this embodiment will be specifically described.

[0052] FIG. 4 is a diagram showing the relationship between the luminous flux ratio of the effective light and the average angle of the first prism 32a.

[0053] The plurality of first prisms 32a have an inclined surface 132a that reflects and / or refracts light introduced from the light source 21, and a bottom surface 132b that is approximately parallel to the first prism surface 32.

[0054] The bottom surface 132b is a flat surface that is substantially parallel to the first prism surface 32. The bottom surface 132b is preferably a smooth flat surface.

[0055] The slope 132a is inclined so as to gradually narrow the width of the first prism 32a from the first prism surface 32 toward the bottom surface 132b. When the first light guide plate 30 is cut at the first prism surface 32, the cross section of the first prism 32a at the slope 132a is a straight line.

[0056] 3(b) may be used in place of the first prism 32a in the first light guide plate 30. The first prism 32b may have an inclined surface 133a that reflects and / or refracts light introduced from the light source 21, and a bottom surface 133b that is approximately parallel to the first prism surface 32. In this case, the inclined surface 133a may be a curve (e.g., a part of a spherical surface) such that the cross section of the first prism 32b when the first light guide plate 30a is cut at the first prism surface 32 is recessed in an arc shape with respect to a second imaginary line described later.

[0057] As shown in (a) and (b) of Figure 6 described later, in a cross section of the multiple first prisms 32a, 32b cut by a plane perpendicular to the first prism surface 32, the depth of the first prisms 32a, 32b is H, the width of the prism opening is D, a second imaginary line is drawn starting from point A so that the angle formed by the second imaginary line connecting point A, which is one of the two ends of the prism opening, and point B, which is the other, is the same as the average angle α of the first prisms 32a, 32b, and point E, which is located on the second imaginary line closer to the light exit surface 33 than the bottom surfaces 132b, 133b of the first prisms 32a, 32b, is at a position where a third imaginary line starting from point B connecting point E and the second imaginary line is perpendicular to the third imaginary line, and 35≦α≦65 H / h≦0.2

number

[0058] The first virtual line is a straight line connecting point A and point B. The second virtual line is a straight line connecting point A and point E. The second virtual line includes one end of bottom surfaces 132b, 133b and the end portions of bottom surfaces 132b, 133b on the point A side. The third virtual line is a straight line connecting point E and point B. The perpendicular line is a straight line connecting point E and point C.

[0059] The average angle α is represented by the angle averaged over the first prisms 32a and 32b between the inclined surfaces 132a and 133a of the first prisms 32a and 32b and the approximate first prism surface 32 (first prism surface 32 considered as a plane). Specifically, the average angle α is represented by the angle between a line connecting point A and the end of the bottom surface 132b or 133b on the point A side, and the opening surface of the first prisms 32a and 32b. In FIGS. 6(a) and 6(b), which will be described later, the average angle α is represented by the angle between a first virtual line and a second virtual line. Therefore, even if the inclined surface 133a shown in FIG. 6(b) has a curved, concave arc shape, the average angle is represented by the angle between the first virtual line connecting points A and B and the second virtual line connecting points A and E.

[0060] Furthermore, point E is the intersection of the first and second virtual lines when the angle between the first and second virtual lines is set to be a right angle. In other words, when the average angle α of first prisms 32a, 32b at point A and a straight line (second virtual line) connecting point A and the end of bottom surfaces 132b, 133b on the point A side are set, point E is the intersection of a perpendicular line drawn from point B to this straight line.

[0061] Here, the reason for determining 35≦α≦65 will be explained with reference to FIG.

[0062] 4, the horizontal axis represents the average angle of the first prism 32a, and the vertical axis represents the luminous flux ratio of effective light (effective luminous flux ±10° / total luminous flux). The effective luminous flux ±10° is the luminous flux within a field angle of ±10° with respect to the normal to the first prism surface 32. The open circles represent the average angle and luminous flux ratio of effective light when the first prism 32a is frustum-shaped, and the closed circles represent the average angle and luminous flux ratio of effective light when the first prism 32a is frustum-shaped with a portion of the spherical surface on the slope 132a.

[0063] For example, when the luminous flux ratio of effective light at which the imaging device 5 or the observer can visually recognize the object is set as 4% to 5% or more, the average angle of the first prism 32a is 35 to 65°. For this reason, the range 35≦α≦65 is set.

[0064] Next, the reason for setting H / h≦0.2 will be explained with reference to FIG.

[0065] FIG. 5 is a diagram showing the relationship between the luminous flux ratio of the inhibiting light and H / h.

[0066] 5, the horizontal axis represents H / h, and the vertical axis represents the luminous flux ratio of the inhibited light (inhibited luminous flux ±10° / effective luminous flux ±10°). The inhibited light includes light that is not emitted from the light emitting surface 33 but is introduced into the first light guide plate 30, and is then directly emitted from the first prism 32a, external light reflected by the first prism surface 32, etc. The inhibited luminous flux ±10° is the luminous flux within a viewing angle of ±10° with respect to the normal to the first prism surface 32. The open circles indicate the case where the average angle when the first prism 32a is in a truncated cone shape is 37.5°, the black circles indicate the case where the average angle when the first prism 32a is in a truncated cone shape is 47.5°, the open squares indicate the case where the average angle when the first prism 32a is in a truncated cone shape is 55°, the black squares indicate the case where the average angle when the first prism 32a is in a truncated cone shape is 62.5°, and the black diamonds indicate the case where the first prism 32a is in a truncated cone shape with part of the spherical surface on the inclined surface 132a.

[0067] In order to obtain a small ratio of inhibited light to effective luminous flux and a constant effective luminous flux, H / h was set to 0.2 or less.

[0068] Furthermore, with reference to FIG. 6, a method for deriving (Equation 1) will be described.

[0069] Fig. 6 is a cross-sectional view showing first prisms 32a and 32b for explaining formula 1. Fig. 6(a) shows a case where the cross section of first prism 32a when first light guide plate 30 is cut at first prism surface 32 has a trapezoidal shape that tapers from first prism surface 32 toward light exit surface 33. Fig. 6(b) shows a case where the cross section of first prism 32b when first light guide plate 30a is cut at first prism surface 32 has a trapezoidal shape that tapers with an inclined surface 133a and a bottom surface 133b that are concave in an arc shape (for example, a part of a spherical surface).

[0070] Given point E, which is perpendicular to the aperture surfaces of first prisms 32a and 32b and is located at the right corner (tip) of an imaginary right-angled triangle, point C, where a perpendicular line drawn from point E to the aperture surfaces of first prisms 32a and 32b intersects with the aperture surfaces of first prisms 32a and 32b, point A, which is located at one end of the width of the prism aperture, and point B, which is located at the other end of the width of the prism aperture, distance D1 between point A and intersection C and distance D2 between intersection C and point B are as follows: D=D1+D2 (Formula 2) The aperture plane is an imaginary plane that forms the apertures of the first prisms 32a and 32b.

[0071] The angle β of the imaginary right triangle at point B is β=90-α (Equation 3) It is shown as follows.

[0072] In this case, the distance D1 is calculated from equations (2) and (3).

number

[0073] Distance D2 is calculated from equations (2) and (3).

number

[0074] In this case, the distance D is calculated from equations (4) and (5).

number

[0075] Then, (Equation 1) is derived from (Equation 6).

[0076] Next, as shown in FIGS. 7A and 7B, the surface light source luminaire 3a may further include a second light guide plate 230. As shown in FIG.

[0077] Fig. 7A is a cross-sectional view of a surface light source illuminating device 3a having a first light guide plate 30 and a second light guide plate 230. Fig. 7B is a cross-sectional view of the first light guide plates 30, 30a and the second light guide plates 23, 230a0 for explaining first prisms 32a, 32b and second prisms 232, 233.

[0078] 7B(a) shows a case where a cross section of a first prism 32a when the first light guide plate 30 is cut at the first prism surface 32 forms a trapezoidal shape tapered by a linear inclined surface 132a and a bottom surface 132b. Also, a cross section of a second prism 232 when the second light guide plate 230 is cut at the second prism surface 234 forms a trapezoidal shape tapered by a linear inclined surface 232a and a top surface 232b. FIG. 7B(b) shows a case where a cross section of a first prism 32b when the first light guide plate 30a is cut at the first prism surface 32 forms a trapezoidal shape tapered by a curved inclined surface 133a that is recessed in an arc shape (for example, a part of a spherical surface) and a bottom surface 133b. In addition, in the cross section of the second prism 233 when the second light guide plate 230a is cut at the second prism surface 234, the slope 233a is an arc-shaped concave curve (e.g., part of a spherical surface) and the tip surface 233b form a tapered trapezoidal shape.

[0079] 7A and 7B (a), the second light guide plate 230 has a second prism surface 234 that is inversion symmetric with respect to the first prism surface 32 of the first light guide plate 30, and a light exit surface 235. Light that has passed through the second light guide plate 230 is emitted from the light exit surface 235. The light exit surface 235 is the surface opposite to the second prism surface 234, and faces the imaging device 5 or the viewer. A plurality of convex second prisms 232 are formed on the second prism surface 234.

[0080] The plurality of second prisms 232 have an inclined surface 232 a that reflects and / or refracts light introduced from the light source 21 and a tip surface 232 b that is approximately parallel to the second prism surface 234 .

[0081] The tip surface 232b is substantially parallel to the first prism surface 32 and is flat and substantially parallel to the second prism surface 234. The tip surface 232b is preferably a smooth flat surface.

[0082] The slope 232a is inclined from the second prism surface 234 toward the tip surface 232b so as to gradually narrow the width of the second prism 232. The slope 232a is such that when the first light guide plate 30 is cut at the first prism surface 32, the cross section of the first prism 32a is a straight line.

[0083] 7B(b) may be used in place of the first prism 32a and the second prism 232 in the first light guide plate 30 and the second light guide plate 230. The first prism 32b and the second prism 233 may have an inclined surface 133a that reflects and / or refracts the light introduced from the light source 21 and a bottom surface 133b that is approximately parallel to the first prism surface 32. The second prism 233 may have an inclined surface 233a that reflects and / or refracts the light introduced from the light source 21 and a tip surface 233b that is approximately parallel to the second prism surface 234. In this case, the inclined surfaces 133a, 233a may be curves (e.g., parts of spherical surfaces) such that the cross sections of the first prism 32b and the second prism 233 when the first light guide plate 30 and the second light guide plate 230a are cut at the first prism surface 32 and the second prism surface 234 are concave in an arc shape relative to the second imaginary line.

[0084] 7A and 7B (a), there is a one-to-one correspondence between the multiple convex second prisms 232 of the second light guide plate 230 and the multiple concave first prisms 32a of the first light guide plate 30. Therefore, the multiple second prisms 232 of the second light guide plate 230 and the multiple first prisms 32a of the first light guide plate 30 are the same in number and are formed at the same positions.

[0085] Furthermore, when the plurality of second prisms 232 of the second light guide plate 230 and the plurality of first prisms 32a of the first light guide plate 30 are fitted together, a small gap is formed between the second prisms 232 and the first prisms 32a. In other words, an air layer is disposed between the plurality of first prisms 32a of the first light guide plate 30 and the plurality of second prisms 232 of the second light guide plate 230.

[0086] Therefore, the first light guide plate 30 and the second light guide plate 230 have surface shapes in which the concaves and convexes are essentially reversed, and the shape and size of the multiple first prisms 32a of the first light guide plate 30 are similar to the shape and size of the multiple second prisms 232 of the second light guide plate 230.

[0087] Therefore, the average angle α of the first prisms 32a of the first light guide plate 30 and the average angle α of the second prisms 232 of the second light guide plate 230 are the same.

[0088] The plurality of first prisms 32a may be convex, or the plurality of first prisms 32a may be concave.

[0089] A light-absorbing material 240 that absorbs light may be arranged on the end face of the second light guide plate 230. The light-absorbing material 240 may be a light-absorbing layer applied to the end face of the second light guide plate 230, or a sheet-like or film-like light-absorbing member may be arranged on the end face of the second light guide plate 230. In other words, the light-absorbing material 240 may not be arranged on the incident end face of the first light guide plate 30, but the light-absorbing material 240 may be arranged on the end face of the second light guide plate 230.

[0090] The case of FIG. 7B(b) is similar to the case of FIG. 7B(a) described above.

[0091] The surface light source luminaire 3a having the first light guide plate 30 and the second light guide plate 230 has a light distribution as shown in FIG.

[0092] FIG. 8 is a diagram showing the light distribution of a surface light source illuminating device 3a having a first light guide plate 30 and a second light guide plate 230. As shown in FIG.

[0093] In the surface light source illuminating device 3a having the first light guide plate 30 and the second light guide plate 230, the luminous flux ratio of the inhibiting light emitted to the outside from the second light guide plate 230 was approximately 11%. This is thought to be because, in a structure in which the first light guide plate 30 and the inversion-symmetric second light guide plate 230 are fitted together, light directly emitted from the first prism 32a of the first light guide plate 30 is reflected by the second prism 232 of the second light guide plate 230 through an air layer, increasing the amount of light returned to the first prism surface 32 of the first light guide plate 30. Therefore, in the surface light source illuminating device 3a having the first light guide plate 30 and the second light guide plate 230, an increase in the inhibiting light can be further suppressed.

[0094] The first light guide plate 30 and the second light guide plate 230 of the surface light source illuminating device 3a are manufactured using stampers made from the same master, as shown in FIG.

[0095] FIG. 9 is a diagram illustrating a method for manufacturing the first light guide plate 30 and the second light guide plate 230. As shown in FIG.

[0096] First, as shown in FIG. 9(a), a master substrate 100 is prepared, which serves as a master for producing the first light guide plate 30 and the second light guide plate 230.

[0097] 9(b), a father stamper 101 is produced as a first stamper based on this master substrate 100. The concave-convex shape of the father stamper 101 is an inverted shape of the concave-convex shape of the master substrate 100.

[0098] 9(c), a mother stamper 102 is produced as a second stamper based on the father stamper 101. The concave-convex shape of the mother stamper 102 is an inverted shape of the concave-convex shape of the father stamper 101. In this case, it is preferable to produce multiple mother stampers 102 from one father stamper 101.

[0099] 9(d), a son stamper 103 is fabricated as a third stamper based on the mother stamper 102. The recessed and projected shape of the son stamper 103 is an inverted shape of the recessed and projected shape of the mother stamper 102. In this case, it is preferable to fabricate multiple son stampers 103 from one mother stamper 102.

[0100] The first light guide plate 30 can be produced by a transfer method using a sun stamper 103. For example, the first light guide plate 30 can be produced by injection molding using a mold incorporating the sun stamper 103. In this case, by using multiple sun stampers 103, multiple first light guide plates 30 can be produced simultaneously.

[0101] The second light guide plate 230 can be produced by a transfer method using a mother stamper 102. For example, the second light guide plate 230 can be produced by injection molding using a mold incorporating the mother stamper 102. In this case, by using a plurality of mother stampers 102, a plurality of second light guide plates 230 can be produced simultaneously.

[0102] In this way, the first light guide plate 30 and the second light guide plate 230 are manufactured using stampers made from the same master. In other words, the first light guide plate 30 and the second light guide plate 230 can be manufactured simply by switching the stampers. In this embodiment, the first light guide plate 30 and the second light guide plate 230 are manufactured by injection molding using a mold incorporating stampers made from the same master. The first light guide plate 30 and the second light guide plate 230 manufactured in this way have shapes in which concave prisms and convex prisms fit together.

[0103] <Action and effect> Next, the effects of the surface light source illumination devices 3, 3a in this embodiment will be described.

[0104] First, the problems encountered in the past will be described with reference to FIG.

[0105] 10 is a diagram for explaining the interfering light emitted from the first prism of the light guide plate of the comparative example, in which the observation light is indicated by a solid line and the interfering light is indicated by a dashed line.

[0106] As shown by the solid line in Figure 10, if the cross section of the first prism when cutting the first light guide plate at the first prism surface is triangular (e.g., conical or triangular grooved), the light that becomes the observation light is reflected by the slope on one side and proceeds toward the light exit surface. However, as shown by the dashed line in Figure 10, the light that becomes the interference light is directly emitted from the slope on one side to the outside of the light guide plate. In this case, the light that enters the slope on one side near the bottom of the first prism is directly emitted from the slope on one side to the outside of the light guide plate, reflected by the slope on the other side, and proceeds toward the imaging device or the observer. In this case, the amount of interference light directed toward the imaging device or the observer increases, making it difficult for the imaging device or the observer to recognize the object due to the interference light, resulting in a decrease in the accuracy of the appearance inspection.

[0107] Therefore, as described above, the surface light source illumination device 3, 3a of technique 1 according to this embodiment includes the light source 21, the first light guide plate 30, 30a having the light source 21, the light incident end surface 31 into which the light emitted by the light source 21 is introduced, the light exit surface 33 that outputs the introduced light, and the first prism surface 32 that is a surface facing the light exit surface 33 and on which a plurality of first prisms 32a, 32b that reflect and / or refract light are formed, and the plurality of first prisms 32a, 32b are recesses having inclined surfaces 132a, 133a that reflect and / or refract the light introduced from the light source 21 and bottom surfaces 132b, 133b that are approximately parallel to the first prism surface 32, and the plurality of first prisms 32a, 32b is cut along a plane perpendicular to first prism surface 32, the depth of first prisms 32a and 32b is H, the width of the prism opening is D, a second imaginary line is drawn starting from point A so that the angle between it and a first imaginary line connecting point A, which is one of the two ends of the prism opening, and point B, which is the other end, is the same as the average angle α of first prisms 32a and 32b, and point E, which is located on the second imaginary line closer to light exit surface 33 than bottom surfaces 132b and 133b of first prisms 32a and 32b, is located at a position where a third imaginary line connecting point E with point B as the starting point, and the second imaginary line are perpendicular to each other, and the distance from point E to point C when a perpendicular line is drawn from point E to the first imaginary line is h. 35≦α≦65 H / h≦0.2

number

[0108] 3(a) and 3(b), the light indicated by the dashed lines that is directly incident on the inclined surfaces 132a and 133a on one side is likely to be emitted directly to the outside of the first light guide plates 30 and 30a without being reflected by the inclined surfaces 132a and 133a on the other side. This makes it possible to suppress an increase in the interfering light that is reflected by the inclined surfaces 132a and 133a on the other side and heads toward the imaging device 5 or the viewer.

[0109] 3(a) and 3(b), light indicated by a solid line that is incident on first prism surface 32 is reflected and further reflected by inclined surfaces 132a and 133a on one side toward light exit surface 33, and is emitted from light exit surface 33 to illuminate the object. The light irradiated onto the object is reflected and passes through first light guide plates 30 and 30a, and is irradiated onto imaging device 5 or an observer. This allows imaging device 5 or an observer to observe the object through first light guide plates 30 and 30a.

[0110] Therefore, according to the present disclosure, it is possible to irradiate the object with a sufficient amount of observation light while suppressing an increase in the interfering light that directly exits from the first prism surface 32.

[0111] Furthermore, the surface light source illumination device 3, 3a of Technique 2 according to this embodiment is the surface light source illumination device 3, 3a described in Technique 1. In this case, the coverage of the multiple first prisms 32a, 32b arranged on the first prism surface 32 is 20% or more and 50% or less.

[0112] According to this, if the coverage of the multiple first prisms 32a, 32b arranged on the first prism surface 32 is 20% or more, the imaging device 5 or the observer can irradiate the object with enough light to observe the object.

[0113] Furthermore, if the coverage rate of the multiple first prisms 32a, 32b arranged on the first prism surface 32 is 50% or less, the bottom surfaces 132b, 133b of the first prisms 32a, 32b are flat, smooth surfaces, so that the imaging device 5 or the observer can observe the object through the first light guide plates 30, 30a.

[0114] Furthermore, the surface light source illumination device 3, 3a of Technology 3 according to this embodiment is the surface light source illumination device 3, 3a described in Technology 1 or 2. In this case, a plurality of light sources 21 are provided so that light is introduced into the first light guide plate 30, 30a from at least two directions, and a plurality of first prisms 32a, 32b are circular in plan view.

[0115] For example, if light emitted by the light source 21 is introduced into one incident end face of the first light guide plate 30, 30a and the other incident end face of the first light guide plate 30, 30a, it is possible to impart symmetry to the brightness of the light emitted from the light exit surface 33. This makes it possible to suppress problems when the imaging device 5 or the observer observes an object through the first light guide plate 30, 30a.

[0116] Furthermore, the surface light source illumination device 3, 3a of Technology 4 according to this embodiment is the surface light source illumination device 3, 3a described in Technology 1 or 2. In this case, a plurality of light sources 21 are provided so that light is introduced into the first light guide plate 30, 30a from two or four directions, and a plurality of first prisms 32a, 32b are rectangular in plan view.

[0117] For example, if light emitted by the light source 21 is introduced into one incident end face of the first light guide plate 30, 30a and the other incident end face of the first light guide plate 30, 30a, it is possible to impart symmetry to the brightness of the light emitted from the light exit surface 33. This makes it possible to suppress problems when the imaging device 5 or the observer observes an object through the first light guide plate 30, 30a.

[0118] The surface light source illuminating device 3, 3a of Technique 5 according to the present embodiment is the surface light source illuminating device 3, 3a according to any one of Techniques 1 to 4. In this case, an anti-reflection coating or an anti-reflection film is laminated on the light exit surface 33.

[0119] This allows a portion of the light that is reflected or refracted by the first prisms 32a and 32b and passes through the light exit surface 33 to be reflected by the light exit surface 33, thereby suppressing an increase in the interfering light that is irradiated onto the imaging device 5 or the observer. The surface light source illuminating device 3, 3a of Technology 6 according to the present embodiment is the surface light source illuminating device 3, 3a according to any one of Technologies 1 to 4. In this case, an anti-reflection coating, an anti-reflection film, or an anti-reflection plate is laminated on the first prism surface 32.

[0120] This makes it possible to prevent external light from being reflected by the first prism surface 32 and becoming interfering light that interferes with the imaging device 5 or the observer.

[0121] The surface light source illumination device 3, 3a of Technology 7 according to this embodiment is the surface light source illumination device 3, 3a according to any one of Technologies 1 to 6. In this case, the surface light source illumination device 3, 3a includes a housing 10 that houses the light source 21 so that light emitted by the light source 21 is introduced to the light incident end surface 31 and supports the edges of the first light guide plates 30, 30a, and the inner surface of the housing 10 is subjected to surface treatment with a black material or a light absorbing surface treatment.

[0122] This makes it possible to absorb leak light, stray light, and the like from the light source 21, and thus to prevent the light from becoming an obstruction that would obstruct the imaging device 5 or the observer.

[0123] Furthermore, the surface light source illumination device 3, 3a of Technology 8 according to this embodiment is the surface light source illumination device 3, 3a described in Technology 7. In this case, the housing 10 is a frame having a first opening 11 and a second opening 12 facing the first opening 11, and supports the first light guide plates 30, 30a so that the first prism surface 32 is exposed from the first opening 11 and the light exit surface 33 is exposed from the second opening 12.

[0124] According to this, the imaging device 5 or the observer can observe the object by positioning the imaging device 5 or the observer so as to face the first opening 11 and positioning the object so as to face the second opening 12. Therefore, the surface light source illumination device 3, 3a is useful as an illumination device for inspection.

[0125] Furthermore, the surface light source illumination device 3a of Technology 9 according to this embodiment is the surface light source illumination device 3a according to any one of Technologies 1 to 8. In this case, the plurality of first prisms 32a, 32b are concave, and a plurality of convex second prisms 232, 233 are formed on a second prism surface 234, and second light guide plates 230, 230a are provided with the convex second prism surface 234 that is inversion-symmetric with respect to the first prism surface 32 of the first light guide plate 30, 30a, and the plurality of first prisms 32a, 32b of the first light guide plate 30, 30a and the plurality of second prisms 232, 233 of the second light guide plate 230, 230a are arranged to fit together with an air layer interposed therebetween.

[0126] This makes it possible to suppress light emitted from the first prism surfaces 32 of the first light guide plates 30, 30a while maintaining the transparency and light transmittance of the surface light source illuminating device 3a.

[0127] Moreover, the surface light source illuminating device 3a of Technique 10 according to the present embodiment is the surface light source illuminating device 3a described in Technique 9. In this case, a light absorbing material 240 that absorbs light is disposed on the end faces of the second light guide plates 230 and 230a.

[0128] This makes it possible to absorb light that is repeatedly reflected within the second light guide plates 230, 230a.

[0129] Furthermore, the manufacturing method of the surface light source illumination device 3, 3a of Technology 11 relating to this embodiment is a manufacturing method of the surface light source illumination device 3, 3a including a first light guide plate 30, 30a having a first prism surface 32 on which a plurality of concave first prisms 32a, 32b are formed, and a second light guide plate 230, 230a having a second prism surface 234 on which a plurality of convex second prisms 232, 233 are formed, and the first light guide plate 30, 30a and the second light guide plate 230, 230a are manufactured using stampers made from the same master.

[0130] This allows the first light guide plates 30, 30a and the second light guide plates 230, 230a to be manufactured at low cost.

[0131] (Other variations, etc.) Although the surface light source illumination device according to the present disclosure has been described above based on the above-mentioned embodiments, the present disclosure is not limited to these embodiments. As long as the modifications do not deviate from the spirit of the present disclosure, modifications that are conceivable by those skilled in the art may also be included in the scope of the present disclosure.

[0132] In addition, this disclosure also includes forms obtained by making various modifications to the embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions of the embodiments within the scope that does not deviate from the intent of this disclosure. [Explanation of symbols]

[0133] 3, 3a surface light source lighting device 10. Cabinet 11 First opening 12 Second opening 21 Light source 30, 30a 1st light guide plate 31 Light incident end face 32 First prism surface 32a, 32b First prism 33 Light exit surface 132a, 133a slopes 132b, 133b bottom 230, 230a 2nd light guide plate 232, 233 Second prism 234 Second prism surface 240 Light-absorbing materials

Claims

1. A light source and a first light guide plate having a light incident end surface into which light emitted from the light source is introduced, a light exit surface that outputs the introduced light, and a first prism surface that faces the light exit surface and has a plurality of first prisms that reflect and / or refract light formed thereon; the plurality of first prisms are recesses each having an inclined surface that reflects and / or refracts light introduced from the light source and a bottom surface that is approximately parallel to the first prism surface, In a cross section obtained by cutting a plurality of the first prisms along a plane perpendicular to the first prism surface, the depth of the first prism is H, the width of the prism opening is D, a second imaginary line is drawn starting from point A so that the angle formed with a first imaginary line connecting point A, which is one of the ends of the prism opening, and point B, which is the other end of the prism opening, is the same as the average angle α of the first prism, and point E on the second imaginary line, which is located closer to the light exit surface than the bottom surface of the first prism, is at a position where a third imaginary line connecting point E with point B as the starting point is perpendicular to the second imaginary line, and h is the distance to an intersection C when a perpendicular line is drawn from point E to the first imaginary line, ３５ ≦ α ≦ ６５ H / h≦0.2 [Equation 1] fulfill Surface light source lighting device.

2. The coverage of the first prisms arranged on the first prism surface is 20% or more and 50% or less.

2. The surface light source lighting device according to claim 1.

3. a plurality of the light sources arranged so that light is introduced into the first light guide plate from at least two directions; The first prisms are circular in plan view.

3. The surface light source lighting device according to claim 1 or 2.

4. a plurality of the light sources arranged so that light is introduced into the first light guide plate from two or four directions; The plurality of first prisms are rectangular in plan view.

3. The surface light source lighting device according to claim 1 or 2.

5. An anti-reflection coating or an anti-reflection film is laminated on the light exit surface.

3. The surface light source illumination device according to claim 1 or 2.

6. An anti-reflection coating, an anti-reflection film, or an anti-reflection plate is laminated on the first prism surface.

3. The surface light source illumination device according to claim 1 or 2.

7. a housing that accommodates the light source so that light emitted from the light source is introduced into the light incident end surface and supports an edge of the first light guide plate; The inner surface of the housing is subjected to a surface treatment of a black material or a light-absorbing surface treatment.

3. The surface light source illumination device according to claim 1 or 2.

8. The housing includes: a frame having a first opening and a second opening opposite the first opening, The first light guide plate is supported so that the first prism surface is exposed from the first opening and the light exit surface is exposed from the second opening.

8. The surface light source illumination device according to claim 7.

9. the first prisms are concave; a second light guide plate having a second prism surface that is inversion symmetric with respect to the first prism surface of the first light guide plate; a plurality of convex second prisms are formed on the second prism surface; The first prisms of the first light guide plate and the second prisms of the second light guide plate are arranged to fit together with an air gap therebetween.

3. The surface light source illumination device according to claim 1 or 2.

10. A light absorbing material that absorbs light is disposed on an end surface of the second light guide plate. The surface light source illumination device according to claim 9 .

11. A method for manufacturing a surface light source illumination device including a first light guide plate having a first prism surface on which a plurality of first concave prisms are formed, and a second light guide plate having a second prism surface on which a plurality of second convex prisms are formed, the method comprising: The first light guide plate and the second light guide plate are manufactured using stampers made from the same master. A method for manufacturing a surface light source lighting device.

Images