JP5481223B2 - Lighting device and lens sheet - Google Patents

Description

  The present invention relates to an illumination device configured by combining a white light source and a sheet-like condenser lens.

  Conventionally, by arranging a sheet-like condensing lens (hereinafter referred to as a lens sheet) such as a Fresnel lens in front of the light source (in the emission direction), the orientation of the emitted light is controlled to increase the illuminance (increase the brightness). The illustrated illuminating device is known (for example, refer patent document 1).

  The illumination device disclosed in Patent Document 1 is configured by arranging a lens sheet (Fresnel lens) 72 in front of the linear light source 71 (upward in the drawing) as shown in FIG. The lens sheet 72 is formed with a plurality of refractive prisms (Fresnel lenses) having a refracting action at the central portion, which is a region near the optical axis 73, and has a reflecting action at the outer peripheral portion (peripheral portion) on the outer peripheral side of the central portion. A plurality of reflection prisms (TIR lenses; Total Internal Reflection lenses) are formed.

  In this way, by forming a refractive prism in the center of the lens sheet and forming a reflective prism on the outer periphery, the lens sheet is higher than when using a lens sheet with only the refractive prism or only the reflective prism. Illumination light with high efficiency (high intensity of emitted light and high illuminance) and excellent intensity uniformity can be obtained. This is because the output light refracted by the refraction prism has a high intensity at the center of the lens sheet, but tends to decrease at the outer periphery, whereas the output light reflected by the reflection prism is the center. This is because the strength is small at the portion, but the strength tends to increase at the outer peripheral portion.

JP 2002-221605 A

  By the way, in recent years, attention has been paid to illumination devices such as downlights and spotlights that use small light emitting diodes (LEDs) excellent in environmental compatibility as light sources. As an LED capable of obtaining white light, an LED chip that emits blue light (center wavelength: 410 nm to 480 nm) (blue light) and a yellow light (wavelength range: 480 nm to 700 nm) light (yellow light) that absorbs blue light. A so-called pseudo white LED, which is a combination of a yellow phosphor that is converted into (1) is widely used.

  Therefore, the present inventors have configured a lighting device by combining a surface-mounted pseudo white LED and a lens sheet for point light source (LED) disclosed in Patent Document 1 (paragraph 0046 of Patent Document 1). Although illumination light with excellent illuminance was obtained, color unevenness was observed in the illumination light and the appearance was poor. Specifically, the light transmitted through the lens sheet was white as a whole, but was somewhat blue at the center and somewhat yellow at the outer periphery.

  As shown in FIG. 9, this uneven color is the light that travels substantially parallel to the optical axis among the blue light emitted from the LED chip 83 mounted on the electrode terminal 82 on the bottom surface of the recess of the lamp house 81. This is because the optical path length passing through the sealing body 85 in which the yellow phosphor 84 is dispersed is different between the light L2 that is inclined and the light L2 that is inclined. That is, the light L1 has a relatively small ratio of being converted into yellow light by the yellow phosphor 84 because the optical path length passing through the sealing body 85 is shorter than the light L2, and thus the light L1 has a blueish white color. It becomes light (blue-white light). On the other hand, the light L2 has a relatively high ratio of being converted to yellow light by the yellow phosphor 84 because the optical path length passing through the sealing body 85 is longer than that of the light L1, so that the yellowish white It is considered to be light (yellowish white light).

  Therefore, the present invention has been made in view of the above situation, and an object of the present invention is to provide an illuminating device that has favorable illuminance (luminance) and reduced color unevenness.

Therefore, in order to solve the above-described problem, an illumination device according to the present invention includes a light source that emits white light radially toward the front, and a plurality of concentric circles that are arranged in front of the light source and have an optical axis as a center. And a lens sheet that controls the orientation of the white light emitted from the light source, the light source emitting light of a predetermined wavelength, and the light emission A phosphor that emits fluorescence upon receiving light of the predetermined wavelength emitted from the element and covers the light emitting element, and the lens sheet has the same wavelength as that of the adjacent prism. It includes the prisms having different focal lengths for light .

According to the invention, a lens sheet disposed in front of the white light source, the focal length contains pulp rhythm different from each other with respect to light of the same wavelength from the adjacent prism. By the way, the light incident on each of the plurality of prisms is guided forward at an angle with respect to the optical axis at an angle corresponding to the focal length of each prism. Therefore, each of the lights incident on the prisms having different focal lengths travels forward so as to cross (mix) each other. Therefore, when light with uneven color emitted from a pseudo-white light source composed of a light emitting element and a phosphor is incident on the lens sheet, color mixing (averaging) is performed according to the focal length of each prism. As a result, illumination light with reduced color unevenness can be obtained.

In this case, the lens sheet, at least a portion of the prism of the plurality of prisms may be formed to include a region in which the focal length varies depending on the distance from the optical axis.

As described above, by changing the focal lengths of a plurality of prisms existing in a predetermined region according to the distance from the optical axis, the effect of reducing color unevenness is effectively exhibited, and the design and production of the lens sheet Becomes easier.

In this case, in a region of an optical axis toward a plurality of refraction prism having a refraction effect, preferably the nearly as focal length away from the optical axis is formed to be larger.
According to this invention, light incident on a plurality of refractive prisms having a refracting action formed in the central portion that is a region near the optical axis is incident on the outer peripheral side at various angles with respect to the optical axis according to the incident position. (Inclination angle with respect to the optical axis increases as each of the plurality of refractive prisms is located on the outer peripheral side in the center). As a result, the light emitted from the central portion and the light emitted from the outer peripheral portion, which is a region on the outer peripheral side (outside of the central portion) of the central portion, are mixed with each other, and the effect of reducing color unevenness is more effectively exhibited. Is done. Further, for the reason described later (paragraph 0047), it is possible to obtain much more efficient illumination light.

A plurality of reflecting prisms having a reflecting action may be formed in a region on the outer peripheral side of the region where the plurality of refractive prisms are formed.
In this case, the plurality of reflecting prisms may be formed such that the focal length increases as the distance from the optical axis becomes closer, or the focal length changes randomly regardless of the distance from the optical axis. May be .
According to this invention, the lens sheet has a refractive prism formed in the center (region near the optical axis) and a plurality of reflecting prisms having a reflecting action on the outer periphery (outside of the center). For this reason, as described in the prior art, it is possible to obtain outgoing light with high efficiency and excellent intensity uniformity, and the effect of reducing color unevenness is more effectively exhibited.
In addition, the lens sheet may include a region in which at least some of the plurality of prisms are formed such that the focal length changes randomly regardless of the distance from the optical axis.
Further, the lens sheet may be formed such that all of the plurality of prisms change in focal length in a mode for each region corresponding to the distance from the optical axis.

  In another embodiment of the present invention, the lens sheet may have a flat surface between the adjacent prisms among the plurality of prisms.

  According to this invention, it can be expected that the effect of reducing color unevenness is effectively exhibited, and the design and production of the lens sheet is facilitated.

The light source preferably includes a blue light emitting diode that emits blue light and a phosphor that receives blue light and converts it into yellow light.
The lens sheet according to the present invention includes a light emitting element that emits light of a predetermined wavelength and a phosphor that emits fluorescence by receiving the light of the predetermined wavelength emitted from the light emitting element. A plurality of concentric prisms for controlling the orientation of the white light emitted from the light source. In the lens sheet, the plurality of prisms include the prisms having different focal lengths with respect to light having the same wavelength as the adjacent prisms.
In this case, the plurality of prisms may include a plurality of refraction prisms having a refraction action, or may include a plurality of refraction prisms having a refraction action and a plurality of reflection prisms having a reflection action.

  According to this invention, the illuminating device in which the said effect is exhibited effectively can be manufactured at low cost.

It is sectional drawing which shows the example of whole structure of the illuminating device which concerns on embodiment of this invention. FIG. 3 is a right half sectional view (hatching process is omitted) from the optical axis for explaining the configuration of the lens sheet and the emitted light of the illumination device. It is sectional drawing for demonstrating the shape of the prism of the lens sheet, (a) is a Fresnel prism, (b) is a TIR prism. It is a graph for demonstrating the specific structure and characteristic of the lens sheet, (a) (b) (c) shows the focal length, angle, and light collection efficiency of each prism, respectively. It is a graph for demonstrating the shape of the conventional lens sheet shown in contrast with FIG. 4, (a) (b) (c) shows the focal distance of each prism, an angle, and condensing efficiency, respectively. (A) is a fragmentary sectional view which shows the structure of the some Fresnel prism in the same lens sheet, (b) is a fragmentary sectional view which shows the structure of the some Fresnel prism in the conventional lens sheet shown for a comparison. . It is a fragmentary sectional view showing the modification of the lens sheet. It is sectional drawing explaining the structure of the conventional Fresnel lens, and emitted light (a hatching process is abbreviate | omitted). It is sectional drawing explaining the structure and emitted light of pseudo | simulation white LED.

  Hereinafter, a lighting device 10 according to an embodiment of the present invention will be described with reference to the accompanying drawings. In each drawing, in order to facilitate understanding of the present invention, some components are schematically exaggerated as appropriate, and the actual dimensions, dimensional ratios, shapes, and the like are accurately reflected. There are parts that are not.

  As shown in FIG. 1, the illuminating device 10 controls the orientation of the white light emitted from the LED 11 that is disposed in front of the LED 11 and the LED 11 as a light source that emits white light forward (lower side in the drawing). A lens sheet 21 and a bowl-shaped or bottomed cylindrical reflecting mirror (not shown) that integrally covers the outer edge of the LED 11 and the outer edge of the lens sheet 21 are provided.

  The LED 11 is a pseudo white LED described in the related art. In this embodiment, the LED 11 includes a lamp house 13 formed of a white resin having a truncated conical recess 12 formed in the center, an LED chip 14 that is mounted on the bottom surface of the recess 12 and emits blue light, and the LED chip 14. And a phosphor 15 that emits yellow light (fluorescence) by receiving blue light that is dispersed in the seal 15 and emitted by the LED chip 14. YAG phosphor) 16.

  The sealing body 15 in which the phosphors 16 are dispersed is formed in a truncated cone shape that expands forward from the LED chip 14 side. Therefore, of the light emitted radially from the light emitting surface 17 that is the opening of the lamp house 13, the light emitted substantially parallel to the optical axis (center axis) C is somewhat blueish for the reason described in the prior art. Tend to be white light (blue white light). Further, the light emitted with an inclination with respect to the optical axis C tends to be white light (yellowish white light) with a slight yellowishness.

  Next, the lens sheet 21, which is a characteristic part of the present invention, is formed into a disk shape having a diameter D using a transparent resin (in this embodiment, acrylic resin (refractive index 1.49)) (in this embodiment). Injection molding). The lens sheet 21 illuminates the center of rotation so that the distance between a surface (hereinafter referred to as an opposing surface) 21a facing the LED 11 and the light emitting surface 17 of the LED 11 becomes a predetermined length (hereinafter referred to as an LED-sheet distance) L. They are arranged so as to coincide with the axis C.

In this embodiment, the LED-sheet distance L is substantially equal to the diameter d of the light emitting surface 17 of the LED 11, but it is small (thin) and has the viewpoint of effectively exhibiting the effects of this embodiment to be described later. Therefore, it is preferable to set the diameter to 0.5 to 1.5 times the diameter d. Moreover, it is preferable to set the diameter D of the lens sheet 21 to TAN < ^-1 > (D / 2L) <80 degrees from the same viewpoint.

  A plurality of (multiple) prisms 21 that are concentric with respect to the optical axis C are formed on the facing surface 21 a of the lens sheet 21. A plurality of prisms 21 are formed in a central part A (region A), which is a region near the optical axis C, in the same manner as in the prior art, and a plurality of prisms (generally referred to as m for convenience) (hereinafter, referred to as “prisms”). A Fresnel prism) 23, and a plurality of (generally referred to as n) prisms 24 (hereinafter referred to as TIR prisms) formed on an outer peripheral portion B (region B) that is an outer peripheral side of the central portion A; It is composed of Thereby, illumination light excellent in illuminance can be emitted from the emission surface 21b of the lens sheet 21 (surface facing the facing surface 21a). Note that the boundary between the Fresnel prism 23 and the TIR prism 24 is determined by selecting a prism having a larger proportion (efficiency) of light emitted as effective light from the two types of prisms 23 and 24. .

  In the plural (m + n) prisms 21, as shown by the vertical axis in FIG. 2, the focal length F of the prism 21 continuously changes according to the distance from the optical axis C for each of the regions A and B. It is formed as follows. The focal length of the Fresnel prism 23 is shown as Fa, and the focal length of the TIR prism 24 is shown as Fb. Further, in the same prism 21, the focal length F is constant regardless of the circumferential position.

  The focal length Fa of the Fresnel prism 23 matches the focal length Fa_1 of the first Fresnel prism 23_1 located on the innermost circumference with the LED-sheet distance L. (Although there is a flat surface portion on the inner side of the Fresnel prism 23_1, this surface portion can also be regarded as the first Fresnel prism.) The second and subsequent Fresnel prisms 23 are located on the outer peripheral side. The Fresnel prism 23 is formed such that the focal length Fa increases continuously. Specifically, the focal lengths Fa_1, Fa_k, and Fa_m of the first, kth, and mth (outermost circumference) Fresnel prisms 23_1, 23_k, and 23_m from the inner circumference side are L = Fa_1. <Fa_k <Fa_m.

  Thus, by setting the focal length Fa of each Fresnel prism 23, the light La_1 passing through the Fresnel prism 23_1 located at the innermost circumference travels substantially parallel to the optical axis C. On the other hand, the light La (La_k, La_m) that passes through the Fresnel prism 23 (for example, Fresnel prisms 23_k, 23_m) positioned on the outer peripheral side is inclined toward the outer peripheral side with respect to the optical axis C. The inclination angle tends to increase as the passing Fresnel prism 23 is positioned on the outer peripheral side.

  On the other hand, the focal length Fb of the TIR prism 24 matches the focal length Fb_n of the nth TIR prism 24_n located on the outermost periphery with the LED-sheet distance L. The plurality of TIR prisms 24 located on the inner side of the TIR prism 24_n are formed such that the focal length Fb continuously increases as the TIR prism 24 located on the inner peripheral side. In other words, the TIR prism 24 located on the outer peripheral side is formed such that the focal length Fb continuously decreases. More specifically, the focal lengths Fb_1, Fb_k, and Fb_m of the first, jth, and nth TIR prisms 24_1, 24_j, and 24_n from the inner periphery side are expressed as Fb_1> Fb_j> Fb_n = L. Are in a relationship.

  In this way, by setting the focal length Fb of each TIR prism 24, the light Lb_n passing through the TIR prism 24_n located at the outermost periphery travels substantially parallel to the optical axis C. On the other hand, the light Lb (Lb_1, Lb_j) passing through the TIR prism 24 (for example, the TIR prisms 24_1, 24_j) positioned on the inner peripheral side travels with an inclination toward the inner peripheral side with respect to the optical axis C. The inclination angle tends to increase as the passing TIR prism 24 is located on the inner peripheral side.

  Next, a specific shape of each prism 22 and a specific method for changing the focal length F will be described with reference to FIGS.

  As shown in FIG. 3A, each of the Fresnel prisms 23 is a first Fresnel surface 23a positioned on the inner peripheral side and substantially parallel to the optical axis C, and a second Fresnel prism 23 positioned on the outer peripheral side and inclined with respect to the optical axis C. The Fresnel surface 23b and a part of the facing surface 21a that is a surface orthogonal to the optical axis C are formed in a triangular cross section. The pitch Pa is constant (in the present embodiment, 50 μm) without depending on the prism (without depending on the distance from the optical axis C). Note that the pitch Pa corresponds to the width of the prism in this embodiment. Here, the angle between the first Fresnel surface 23a and the opposing surface 21a (hereinafter referred to as the tilt angle of the first Fresnel surface) is θa1, and the angle between the first Fresnel surface 23a and the second Fresnel surface 23b (hereinafter referred to as the Fresnel apex angle). Is defined as θa2, and the angle formed by the second Fresnel surface 23b and the facing surface 21a (hereinafter, the inclination angle of the second Fresnel surface) is defined as θa3.

  In the case of the Fresnel prism 23, the light La emitted from the LED 11 is refracted when entering the second Fresnel surface 23 b and is emitted forward from the exit surface 21 b of the lens sheet 21. Therefore, the focal length Fa of each Fresnel prism 23 is adjusted by changing the Fresnel apex angle θa2 and the tilt angle θa3 of the second Fresnel surface while keeping the tilt angle θa1 and pitch Pa of the first Fresnel surface constant. Can do.

  On the other hand, as shown in FIG. 3B, each of the TIR prisms 24 is a first TIR surface 24a located on the inner peripheral side and inclined with respect to the optical axis C, and a first TIR surface 24a located on the outer peripheral side and inclined with respect to the optical axis C. The 2TIR surface 24b and a part of the opposing surface 21a which is a surface orthogonal to the optical axis C are formed in a triangular cross section. The pitch Pb is constant (in this embodiment, 50 μm) without depending on the prism. Here, the angle formed by the first TIR surface 24a and the opposing surface 21a (hereinafter referred to as the tilt angle of the first TIR surface) is θb1, the angle formed by the first TIR surface 24a and the second TIR surface 24b (hereinafter referred to as the TIR apex angle) is θb2, and the second angle. The angle formed by the 2TIR surface 24b and the facing surface 21a (hereinafter, the inclination angle of the second TIR surface) is defined as θb3.

  In the case of the TIR prism 24, the light Lb emitted from the LED 11 enters the TIR prism 24 while being refracted by the first TIR surface 24a, is reflected by the second TIR surface 24b, and exits forward from the exit surface 21b of the lens sheet 21. Is done. Therefore, basically, the focal length Fb of each TIR prism 24 can be adjusted by changing the TIR apex angle θb2 and the inclination angle θb3 of the second TIR surface. In this regard, in the present embodiment, the TIR apex angle θb2 (corresponding to the tip angle of the cutting tool) is made constant in consideration of workability when producing a molding die for the TIR prism 24. That is, the value of the inclination angle θb1 of the first TIR surface is changed according to the value of the inclination angle θb3 of the second TIR surface.

  Next, the effect of the illuminating device 10 comprised as mentioned above is demonstrated.

  The illumination device 10 uses, as a light source, an LED 11 of a type that emits white light by combining an LED chip 14 that emits blue light and a phosphor 16 that receives blue light and emits yellow light. In addition, the lens sheet 21 is arranged in front of the LED 11 with a distance L between the LED and the sheet. In the lens sheet 21, a plurality of Fresnel prisms 23 are formed in the central part A, and a plurality of TIR prisms 24 are formed in the outer peripheral part B. For this reason, the white light emitted from the LED 11 can be efficiently emitted from the entire area of the emission surface 21b of the lens sheet 21 as in the prior art. As a result, the illumination device 10 having excellent illuminance is realized.

  For the Fresnel prism 23, the focal length Fa_1 of the first Fresnel prism 23_1 located at the innermost circumference is made to coincide with the LED-sheet distance L. The plurality of Fresnel prisms 23 are formed such that the focal distance Fa becomes continuously larger than the LED-sheet distance L as the distance from the optical axis C increases. On the other hand, for the TIR prism 24, the focal length Fb_n of the nth TIR prism 24_n located on the outermost periphery is made to coincide with the LED-sheet distance L. The plurality of TIR prisms 24 are formed such that the focal length Fb is continuously larger than the LED-sheet distance L as the optical axis C is approached.

  For this reason, the light emitted forward from the innermost peripheral portion (Fresnel prism 23_1 and its vicinity) and the outermost peripheral portion (TIR prism 24_n and its vicinity) of the lens sheet 21 travels substantially parallel to the optical axis C. On the other hand, the light incident on the region (inner peripheral side region) excluding the innermost peripheral portion of the region A where the Fresnel prism 23 is formed is at various angles with respect to the optical axis C depending on the incident position. It progresses so as to incline toward the outer periphery. On the other hand, the light incident on the region (outer peripheral region) excluding the outermost peripheral portion of the region B where the TIR prism 24 is formed is inclined at various angles with respect to the optical axis C in accordance with the incident position. Proceed as follows. That is, when the light emitted from the lens sheet 21 is viewed over the entire area, the light emitted from the inner peripheral region and the light emitted from the outer peripheral region travel forward so as to mix with each other.

  By the way, as described above, the light emitted radially from the LED 11 toward the lens sheet 21 is blue-white light that is emitted substantially in parallel with the optical axis C and is inclined with respect to the optical axis C. The light that is turned into yellowish white light. Here, as described above, the light emitted from the lens sheet 21 proceeds so that the light emitted from the inner peripheral region of the lens sheet 21 and the light emitted from the outer peripheral region are mixed with each other. Therefore, blue-white light mainly incident on the inner peripheral side region and yellow-white light mainly incident on the outer peripheral side region are mixed to obtain illumination light with reduced color unevenness that has been a problem in the prior art. Can do.

  Next, in order to deepen the understanding of the lighting device 10 according to the present embodiment, a specific configuration example (product of the present invention) of the lens sheet 21 according to the present embodiment is illustrated in FIGS. 4 (a), 4 (b), and 4 (c). Will be described with reference to FIG. For comparison, a configuration example (comparative product) of the prior art is shown in FIGS. 5 (a), 5 (b) and 5 (c). Both the product of the present invention and the comparative product have an LED-sheet distance of 3 mm and a lens sheet diameter of 20 mm. Moreover, the diameter of the light emission surface of LED is 4.3 mm.

  As shown in FIG. 5A, the comparative product has a fixed focal length of 3 mm (matches the distance between the LED and the sheet) regardless of whether the prism is a Fresnel prism or a TIR prism. On the other hand, in the product of the present invention, as shown in FIG. 4A, the focal length of each Fresnel prism is 3 mm on the innermost peripheral side or the vicinity thereof, but increases at a relatively large rate on the outer peripheral side. Is set to Further, the focal length of each TIR prism is set to gradually increase at a constant rate toward the inner peripheral side. The focal length of the TIR prism located at the innermost circumference (a point having a radius of about 2.4 mm serving as a boundary with the Fresnel prism) is 5 mm. In this way, in order to realize a focal length that continuously changes with respect to the radial direction for each region (in accordance with the distance from the optical axis), the angle of each prism is individually set to the numerical value shown in FIG. It is set. Note that the boundary between the Fresnel prism and the TIR prism in the comparative product is a point having a radius of about 1.6 mm.

  When the illumination device is completed by combining the lens sheet configured as described above and the pseudo white LED, it is possible to reduce the color unevenness to a level where the color unevenness is not substantially observed as compared with the case where the comparative product is used. confirmed.

  Further, as can be seen by comparing FIG. 4C and FIG. 5C, the light collection efficiency (efficiency) is further improved by continuously changing the focal lengths of various prisms, particularly the Fresnel prism, in the radial direction. ) Became larger. In addition, in the case of a Fresnel prism, the condensing efficiency in FIG.4 (c) and FIG.5 (c) is the light which injects into each Fresnel prism (1st Fresnel surface and 2nd Fresnel surface) from LED. It is the ratio of light incident on the second Fresnel surface. In the case of a TIR prism, it is the ratio of the light incident on the second TIR surface and reflected from the light incident on each TIR prism from the LED. That is, the greater the light collection efficiency, the greater the intensity of light that is effective as illumination light.

  The reason why the light collection efficiency is increased by continuously increasing the focal length of the Fresnel prism in the radial direction is considered as follows. That is, when FIG. 4B and FIG. 5B are compared, in the comparative product, the Fresnel apex angle θa2 continuously decreases with respect to the radial direction (the inclination angle θa3 of the second Fresnel surface increases). On the other hand, in the product according to the invention, the peculiarity of inflection around a radius of 0.7 mm is recognized. This peculiarity is reflected in the height of each Fresnel prism. In the product of the present invention, as shown in FIG. 6A, the height H1 of the Fresnel prism is substantially constant at a relatively small value in the radial direction. That is, the area of the first Fresnel surface is substantially constant with a relatively small value in the radial direction.

  In contrast, in the comparative product, as shown in FIG. 6B, the height H2 of the Fresnel prism increases toward the outer peripheral side (H2> H1), and the area of the first Fresnel surface increases toward the outer peripheral side. Since the light incident on the first Fresnel surface is basically unnecessary light (light that does not contribute to illuminance), the light collection efficiency decreases on the outer peripheral side where the area of the first Fresnel surface increases. Therefore, it is considered that the product of the present invention suppresses an increase in the area of the first Fresnel surface on the outer peripheral side compared with the comparative product, and as a result, high efficiency is achieved.

  From these, it is clear that by using the lens sheet 21 according to the present embodiment, it is possible to realize a lighting device with less color unevenness and higher illuminance even when a pseudo white LED is used as a light source. Became.

  As mentioned above, although preferable embodiment of this invention was described, about embodiment, it is not limited above, A various change is possible in the range which does not deviate from the main point of this invention.

  For example, in the above embodiment, the focal length F of each prism 22 is continuously changed with respect to the radial direction for each of the Fresnel prism 23 and the TIR prism 24. However, the present invention is not limited to this. For example, the focal length F of the prism 22 arbitrarily selected from the plurality of prisms 22 or all the prisms 22 may be changed randomly. Even when the prisms 22 are configured in this way, color unevenness can be reduced.

  In the above embodiment, the Fresnel prism 23 and the TIR prism 24 increase or decrease the focal length F of each prism 22 in one direction with respect to the radial direction, but the present invention is not limited to this. Depending on the chromaticity distribution state of the light emitted by the LED 11, for example, in each of the regions A and B, a partial region with an increased focal length F, a partial region with a reduced focal length F, and a focal length F A fixed partial area (an area having a prism that does not differ in focal length from an adjacent prism) may be combined with each other.

  Moreover, in the said embodiment, although the focal distance F of the innermost periphery of the lens sheet 21 and the prism 22 of the outermost periphery is substantially made to correspond to the distance L between LED-sheets, it is not limited to this. It can be set to a value different from the LED-sheet distance L according to the required orientation characteristics of the emitted light.

  Moreover, in the said embodiment, although each prism 23 and 24 is formed without space | interval between adjacent prisms 23 and 24, it is not limited to this. For example, a flat surface 25 perpendicular to the optical axis C may be formed between adjacent prisms 23 and 24 as in a lens sheet 21A shown in FIG. Even when the flat surface 25 is formed in this way, it is expected that the color unevenness is reduced and the light collection efficiency is improved, and the production of the lens sheet is facilitated.

  Moreover, in the said embodiment, although pseudo | simulation white LED11 was used as a light source, you may combine with the light source of another form. Also in this case, reduction in color unevenness and improvement in illuminance are expected.

  In the above embodiment, the lens sheet 21 is formed with the Fresnel prism 23 and the TIR prism 24. For example, when using a light source with relatively strong directivity (a narrow radiation angle range), Only the Fresnel prism 23 may be formed on the lens sheet. Also in this case, the effect of reducing color unevenness and the effect of improving illuminance are exhibited.

10 Lighting device 11 LED
DESCRIPTION OF SYMBOLS 12 Recess 13 Lamp house 14 LED chip 15 Sealing body 16 Phosphor 17 Light emitting surface 21, 21A Lens sheet 21a Opposing surface 21b Output surface 22 Prism 23 Fresnel prism (refractive prism)
23a First Fresnel surface 23b Second Fresnel surface 24 TIR prism (reflection prism)
24a First TIR surface 24b Second TIR surface 25 Flat surface C Optical axis L Distance between LED and sheet

Claims (13)

A light source that emits white light radially toward the front;
A lens sheet that is arranged in front of the light source and has a plurality of concentric prisms centered on the optical axis and controls the orientation of the white light emitted from the light source.
The light source includes a light emitting element that emits light of a predetermined wavelength, a sealing body that covers the light emitting element in which a phosphor that emits fluorescence in response to the light of the predetermined wavelength emitted from the light emitting element is dispersed, Have
The illumination device according to claim 1, wherein the lens sheet includes the prisms having different focal lengths for light having the same wavelength as the adjacent prisms.   2. The illumination device according to claim 1, wherein the lens sheet includes a region in which at least some of the plurality of prisms are formed such that a focal length changes according to a distance from the optical axis.   The illuminating device according to claim 2, wherein a plurality of refractive prisms having a refractive action are formed in a region near the optical axis such that the focal length increases as the distance from the optical axis increases.   The lighting device according to claim 3, wherein a plurality of reflecting prisms having a reflecting action are formed in a region on an outer peripheral side of a region where the plurality of refractive prisms are formed.   The illuminating device according to claim 4, wherein the plurality of reflecting prisms are formed such that a focal distance increases as the optical axis approaches the optical axis.   5. The illumination device according to claim 4, wherein the plurality of reflecting prisms are formed such that a focal length randomly changes regardless of a distance from the optical axis.   2. The illumination device according to claim 1, wherein the lens sheet includes a region in which at least some of the plurality of prisms are formed such that a focal length changes randomly regardless of a distance from the optical axis.   2. The illumination device according to claim 1, wherein the lens sheet is formed such that a focal length of each of the plurality of prisms is changed in a mode for each region according to a distance from the optical axis.   The illumination device according to any one of claims 1 to 8, wherein the lens sheet includes a prism in which a flat surface is formed between adjacent prisms among the plurality of prisms.   10. The light source according to claim 1, wherein the light source includes a blue light emitting diode that emits blue light and a phosphor that receives blue light and converts the light into yellow light. 11. Lighting equipment. A light emitting element that emits light of a predetermined wavelength; and a sealing body that covers the light emitting element in which a phosphor that emits fluorescence in response to the light of the predetermined wavelength emitted from the light emitting element is dispersed. A lens sheet that is arranged in front of a light source that emits white light radially and includes a plurality of concentric prisms for controlling the orientation of the white light emitted from the light source,
The lens sheet, wherein the plurality of prisms include the prisms having different focal lengths for light having the same wavelength as the adjacent prisms. The lens sheet according to claim 11, wherein the plurality of prisms include a plurality of refractive prisms having a refractive action. The lens sheet according to claim 11, wherein the plurality of prisms include a plurality of refraction prisms having a refraction action and a plurality of reflection prisms having a reflection action.

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