JP2012174601A - Lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED lighting device in which a light distribution of an arbitrary beam expansion angle from a narrow angle to a wide angle can be obtained in a high front-face luminance and a high light utilization efficiency even in an LED of a chip-on-board (COB) system with a large emission face.SOLUTION: The LED lighting device equipped with two transparent lenses on a front face of an LED is provided with a lens 3 (a first lens) arranged in the vicinity of the LED 1 of a chip-on-board (COB)system, and a lens 4 (a second lens) arranged farther from the LED 1 than the lens 3 (the first lens). The lens 4 (the second lens) is in free movement in an optical axis direction and can adjust a distance from the lens 3 (the first lens), and when an approximate curvature of an LED side surface of the lens 3 (the first lens) is made C1 and an approximate curvature of an emission side surface is made C2, and when an approximate curvature of an LED side surface of the lens 4 (the second lens) is made C3 and an approximate curvature of an emission side surface is made C4, C1<C2 as well as C3<C4 are satisfied.

Description

  The present invention relates to an illuminating device including two transparent lenses in front of an LED (Light Emitting Diode) light source so as to obtain a light distribution with an arbitrary beam divergence angle.

  Conventionally, the light source of the spotlight has been a light bulb such as halogen, but in recent years, a light emitting diode excellent in power consumption and life has come to be used. Another reason for the progress of light source replacement is that light-emitting diodes have a small light source size and do not lead to an increase in the size of the instrument. Hereinafter, the light emitting diode is referred to as LED.

  Although the luminous efficiency and luminous flux of LEDs are improving year by year, at present, the luminous flux per LED is about 100 [lm], and it is a spotlight that requires several hundred [lm] to several thousand [lm] per unit. A plurality of LEDs are mounted. In a spotlight in which the light source is an LED, for example, as shown in Patent Document 1, a compound lens that has a concave portion including an LED and uses both refraction and reflection is generally used. Since this compound lens is put on each LED, the same number of lenses as the LED to be mounted is required per spotlight.

  On the other hand, in recent years, chip-on-board (COB) type LEDs have been introduced that aim to achieve low cost and high light intensity by mounting and wiring semiconductor light-emitting elements directly on a printed circuit board and sealing them with a transparent resin containing phosphor powder. I have done it. In general, COB is an abbreviation for ChipOnBoard, which is a mounting technology in which an integrated circuit chip is directly attached to a circuit board or the like without processing the integrated circuit chip into a package, and the circuit of the integrated circuit chip is connected to the circuit pattern of the board. is there.

  Hereinafter, the semiconductor light emitting element is referred to as a chip, and the chip-on-board type LED is simply referred to as COB. In COB, since a large number of chips are densely arranged, the light emission area is larger than the conventional one, but a light flux exceeding 1000 [lm] is possible with one COB. For this reason, if the spotlight has a relatively low output, one light beam can be satisfied by one COB.

  In an LED used for lighting, COB also generates pseudo white light by covering a chip emitting blue light with a sealing resin containing yellow phosphor powder, as in the past. That is, when the light emitting surface is observed, there is a region where only the yellow phosphor is present between the chips or on the outer periphery of the densely arranged chips.

JP 2007-5218 A JP 2009-205873 A JP 2008-080348 A JP 2004-145269 A JP 2003-2222795 A

  Covering each LED with the composite lens described above is expensive because the number of lenses required is the number of LEDs. COB requires only one lens, but COB has a large light-emitting surface. Therefore, when this composite lens, which originally assumes a very small light-emitting surface, is applied, the lens must be enlarged and thickened. To do. Since this composite lens is manufactured by injection molding, it takes a long time to mold a thick-walled lens, which is also expensive.

  Further, in the spotlight, a plurality of beam divergence angles are required from a narrow angle around 10 [deg] to a wide angle around 40 [deg]. The above-described compound lens is fixed at approximately one beam divergence angle because zoom does not work. For this reason, a plurality of types of lens lineups having different beam divergence angles are required, and there are problems such as complicated management and having to have more stock. Further, in COB, if it is attempted to minimize the increase in size of the lens, it is difficult to design a narrow-angle lens.

  Furthermore, spotlights using a transparent lens have a problem that the light emitting surface of the LED is projected onto the surface to be irradiated and the image of the chip can be seen. The pseudo-white light is projected at a location where a blue light emitting chip is present under the yellow phosphor, but the yellow light is projected only at a location where only the yellow phosphor is absent. For this reason, color unevenness is likely to occur, for example, a yellow lattice pattern can be seen even on the irradiated surface.

  An object of the present invention is to provide an illuminating device corresponding to a light source such as a chip-on-board type LED having a large light emitting surface. It is another object of the present invention to provide an illuminating device that can select an arbitrary beam divergence angle from a narrow angle to a wide angle and suppress uneven color on the surface to be irradiated.

The lighting device of the present invention is
The first lens,
A second lens,
A light source is attached, and the first lens is arranged in the light output direction of the light from the light source, and further includes a fixed cylinder for arranging the second lens,
The approximate curvature of the surface on the light source side of the first lens is C1,
The approximate curvature of the light exit side surface of the first lens is C2,
The approximate curvature of the surface on the light source side of the second lens is C3,
When the approximate curvature of the light exit side surface of the second lens is C4,
C1 <C2 and C3 <C4
It is characterized by being.

  The illuminating device according to the present invention has an effect that light distribution can be obtained with high front luminous intensity and high light utilization efficiency even in a light source having a large light emitting surface.

(A) is side surface sectional drawing showing the lens arrangement | positioning by the side of a narrow angle of the illuminating device 10 which concerns on Embodiment 1 of this invention. (B) is side surface sectional drawing showing the lens arrangement | positioning by the side of the wide angle of the illuminating device 10 which concerns on Embodiment 1 of this invention. (A) is a figure showing the light distribution at the time of Fig.1 (a). (B) is a figure showing the light distribution at the time of FIG.1 (b). (A) is side surface sectional drawing showing the lens arrangement | positioning by the side of a narrow angle of a 1st comparative example. (B) is side surface sectional drawing showing the lens arrangement | positioning of the wide angle side of a 1st comparative example. (A) is a figure showing the light distribution at the time of Fig.3 (a). (B) is a figure showing the light distribution at the time of FIG.3 (b). (A) is side surface sectional drawing showing the lens arrangement | positioning by the side of a narrow angle of the 2nd comparative example. (B) is side surface sectional drawing showing the lens arrangement | positioning of the wide angle side of a 2nd comparative example. (A) is a figure showing the light distribution at the time of Fig.5 (a). (B) is a figure showing the light distribution at the time of FIG.5 (b). (A) is side surface sectional drawing showing the lens arrangement | positioning by the side of a narrow angle of the illuminating device 10 which concerns on Embodiment 2 of this invention. (B) is side surface sectional drawing showing the lens arrangement | positioning by the side of the wide angle of the illuminating device 10 which concerns on Embodiment 2 of this invention. (A) is a figure showing the color of the to-be-irradiated surface in the illuminating device 10 which concerns on Embodiment 1 of this invention. (B) is a figure showing the color of the to-be-irradiated surface in case the aperture_diaphragm | restriction 7 is not arrange | positioned in the illuminating device 10 which concerns on Embodiment 2 of this invention. (C) is a figure showing the color of the to-be-irradiated surface at the time of arrange | positioning the aperture_diaphragm | restriction 7 in the illuminating device 10 which concerns on Embodiment 2 of this invention. (A) is a figure showing the fly-eye lens provided in S3 surface of the lens 4 which concerns on Embodiment 2 of this invention which arranged the spherical lens in the square lattice form. (B) is a figure showing the lens array which arranged the spherical lens in the hexagonal lattice form provided in S3 surface of the lens 4 which concerns on Embodiment 2 of this invention. (C) is a figure showing the lens array which arranged on the S3 surface of the lens 4 which concerns on Embodiment 2 of this invention, and arranged the donut surface from which a diameter differs concentrically. It is a schematic diagram showing a power arrangement | positioning and the locus | trajectory of a light ray of the optical system which consists of two lenses of this Embodiment 1 of this invention. It is a figure which shows the relationship between COB1 of this Embodiment 1 of this invention, and the curvature radius of the lens 3. FIG. It is a figure which shows the relationship between the focal distance f1 of the lens 3 of this Embodiment 1 of this invention, and the focal distance f2 of the lens 4. FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional side view of a lighting apparatus 10 according to Embodiment 1 of the present invention. The illumination device 10 includes a zoom lens using two lenses, that is, the lens 3 and the lens 4. FIG. 1A is a sectional view showing a lens arrangement on the narrow angle side, and FIG. 1B is a sectional view showing a lens arrangement on the wide angle side.

  A chip-on-board LED (hereinafter referred to as COB) 1 as a light source is formed on a substrate 2 made of a metal such as aluminum, glass epoxy resin, ceramic, or the like. On the substrate 2, a plurality of semiconductor light emitting elements, that is, a plurality of LED chips, are arranged in a circular shape (diameter D). The substrate 2 is fixed to a heat sink (not shown), and is supplied with power from a power supply (not shown) via a connector and a cable, and the COB 1 is lit.

  In front of the COB 1, a lens 3 is arranged close to the lens, and a lens 4 is arranged farther than the lens 3. The lens 3 and the lens 4 are formed of a transparent material such as acrylic or polycarbonate, or a transparent material that transmits light emitted from the COB 1 such as glass.

The fixed cylinder 5 has a hollow bottomed cylindrical shape / bottomed cylindrical shape. In the center of the bottom of the fixed cylinder 5, a COB 1, a substrate 2 and a lens 3 are arranged.
The fixed cylinder 5 is a member for holding the lens 3, and the movable cell 6 is a member for holding the lens 4. The movable cell 6 can be moved in the direction of the optical axis Z with respect to the fixed cylinder 5 by electric or manual operation, whereby the lens 4 can be moved closer to or away from the lens 3. The fixed cylinder 5 and the movable cell 6 are made of die cast such as aluminum or magnesium, or a plastic molded product. The inner cylinder surface of the fixed cylinder 5 is black dyed and further subjected to a light shielding rotation, so that the light scattered or specularly reflected by the inner cylinder surface is different from the original light controlled by the lens 3 and the lens 4. By being emitted, the occurrence of glare is prevented.

Hereinafter, the lens 3 and the lens 4 will be described.
The light emitted from the COB 1 with a completely diffusive light distribution (a light distribution with the same luminance when viewed from any direction) is narrowed in its beam divergence angle by the lens 3 disposed close to the COB 1, and then the lens 4. Then, the light is narrowed again, and is emitted as the final beam divergence angle of the illumination device 10.

  When the lens 4 is arranged farther than the lens 3 as shown in FIG. 1A, a narrow-angle beam is obtained, and when the lens 4 is arranged near the lens 3 as shown in FIG. A wide-angle beam can be obtained.

  FIG. 2 (a) shows the light distribution at the time of FIG. 1 (a), and FIG. 2 (b) shows the light distribution at the time of FIG. 1 (b). The beam divergence angle is about 10 [deg] in FIG. 2A and slightly less than 40 [deg] in FIG. Here, the beam divergence angle is defined as the width (full width at half maximum) of two angles at which the maximum peak luminous intensity, usually a radiation angle of 0 deg, that is, half the luminous intensity of the frontal luminous intensity. Hereinafter, the beam divergence angle refers to the width of this angle. At this time, the luminous flux of COB1 was 1450 [lm], and the size of the light emitting surface of COB1 was a diameter φ10 [mm].

  Although illustration is omitted, when the lens 4 is arranged at an appropriate position between the position of the lens 4 shown in FIG. 1A and the position of the lens 4 shown in FIG. 1B, 20 [deg] or 30 An intermediate beam divergence angle of [deg] is obtained. That is, by moving the lens 4 along the optical axis Z, it is possible to obtain an arbitrary beam divergence angle from a narrow angle of about 10 [deg] to a wide angle of about 40 [deg].

The surface on the COB1 side of the lens 3 is the S1 surface, and the opposite side of the S1 surface, that is, the exit side surface is the S2 surface. Similarly, the surface of the lens 4 on the COB1 side is the S3 surface, and the opposite side of the S3 surface, that is, the exit side surface is the S4 surface. The S1 to S4 surfaces may be aspherical surfaces, but the radii of curvature when the S1 to S4 surfaces are approximated by spherical surfaces are R1 to R4, and the curvatures (approximate curvatures) are C1 to C4, respectively. The curvature C is the reciprocal of the curvature radius R of the approximate spherical surface. C1 to C4 take positive values when the S1 surface to S4 surface are convex surfaces, and take negative values when they are concave surfaces. These curvatures (or approximate curvatures) C1 to C4 have the following relationship.
The approximate curvature of the light source side surface of the lens 3 is C1,
The approximate curvature of the light exit side surface of the lens 3 is C2,
The approximate curvature of the surface of the lens 4 on the light source side is C3,
When the approximate curvature of the light exit surface of the lens 4 is C4,
C1 <C2 and C3 <C4 (Formula 1)

Here, the S1 surface may be a concave surface, and C1 may be a negative value.
The S2 surface must be convex and C2 is always a positive value.
The S3 surface may be concave and C3 may be a negative value.
The S4 surface must be convex and C4 is always a positive value.

  In order to explain the necessity of the relationship of (Formula 1), a first comparative example is shown in FIG. In the first comparative example, there is no lens 3 close to the COB 1, and a light distribution from a narrow angle to a wide angle is made only by the lens 4. FIG. 3A is a sectional view showing a lens arrangement on the narrow angle side, and FIG. 3B is a sectional view showing a lens arrangement on the wide angle side.

  Furthermore, the light distribution obtained in the first comparative example is shown in FIG. FIG. 4 (a) shows the light distribution at the time of FIG. 3 (a), and FIG. 4 (b) shows the light distribution at the time of FIG. 3 (b). In FIG. 2, which is the light distribution according to the first embodiment, the front-intensities at the narrow angle and the wide angle are 19000 [cd] and 3200 [cd], respectively, whereas in FIG. 4, 14000 [cd] and 2200 [cd]. And is significantly lower. That is, it can be seen that the ratio of the luminous flux that illuminates the object to be illuminated out of the luminous flux emitted from COB1, that is, the light utilization efficiency is poor.

When the light distribution is made by only one lens 4, the distance L from the light source COB1 to the lens 4 (S4 surface having the main power in the first comparative example) is the size of the light emitting surface of COB1 ( It is determined by the following equation from the diameter D) and the target beam divergence angle θ.
L≈D / 2 × tan (90 [deg] −θ / 2) (Formula 2)

  For example, when the diameter D = φ10 [mm] of the light emitting surface of COB1 and the beam divergence angle θ = 10 [deg], L≈60 [mm], and the lens 4 (S4 surface) is around 60 [mm] from COB1. Must be placed at a distance. In addition, the size of the lens 4 is often limited by, for example, the size of the hole in the ceiling surface where the lighting device 10 is installed, and the size of the lens 4 is compared with the first embodiment. In the case of the example, both are set to φ70 [mm].

  As described above, since the distance from the COB 1 to the lens 4 and the size of the lens 4 are both limited, in the first comparative example using only one lens 4, the light 4 from the COB 1 is naturally captured by the lens 4. The angle is determined and the light utilization efficiency is limited to a low level. For example, if the diameter D of the light emitting surface of the COB 1 is small as in a conventional LED, the lens 4 can be brought closer to the light source, and the light utilization efficiency can be increased. However, when the light emitting surface is large like COB1, when the lens 4 is brought close to the light source, the beam divergence angle spreads larger than the target value, as can be seen from (Equation 2).

  On the other hand, in the first embodiment, the light emitted from the COB 1 is once narrowed by the lens 3 arranged close to the COB 1 and efficiently enters the lens 4. As described above, since the light emitted from the COB 1 is a perfect diffusion type light distribution, the beam divergence angle is 120 [deg]. For this reason, the lens 3 is preferably disposed as close as possible to the COB 1 as long as the surface of the S1 surface is not melted, deformed or burned, and is squeezed before the light emitted from the COB 1 spreads. If these problems such as melting do not occur, the S1 surface and the COB1 surface may be brought into close contact with each other. Since the surface of the COB 1 is a substantially flat surface, the S1 surface of the lens 3 is preferably a flat surface or a concave surface. Even if it is a convex surface, at least a gentle curvature is preferable compared to the S2 surface. Therefore, it is preferable that C1 <C2.

  As described above, in the first embodiment, the lens 3 that satisfies C1 <C2 is disposed close to the COB1, so that the front luminous intensity is higher than that of the first comparative example as shown in FIGS. High light utilization efficiency has been achieved.

A second comparative example is shown in FIG. FIG. 5A is a sectional view showing a lens arrangement on the narrow angle side, and FIG. 5B is a sectional view showing a lens arrangement on the wide angle side.
In the second comparative example, the lens 4 is designed to satisfy the light distribution on the narrow angle side so that the curvature of the S4 surface of the lens 4 is gentler than the curvature of the S3 surface, that is, in a state where C3> C4. is there. The light distribution obtained in the second comparative example is shown in FIG. 6A shows the light distribution at the time of FIG. 5A, and FIG. 6B shows the light distribution at the time of FIG. 5B. As shown in FIG. 6 (b), it can be seen that the front luminous intensity of the light distribution on the wide-angle side has dropped, and so-called hollows have occurred. This phenomenon is also observed when the beam has an intermediate beam divergence angle of 20 [deg] or 30 [deg], and causes the problem that the center of the irradiated surface is darker than the surroundings. For this reason, a relationship of C3 <C4 is necessary.

  That is, according to the illumination device 10 according to the first embodiment, the lens 3 disposed close to the COB 1 that is the light source, the lens 4 disposed farther than the lens 3, and the lens 4 are brought close to the lens 3. Even in a chip-on-board type LED having a large light emitting surface, the light distribution with an arbitrary beam divergence angle from a narrow angle of about 10 [deg] to a wide angle of about 40 [deg] can be achieved with a high front light intensity. Can be realized with high light utilization efficiency.

  FIG. 10 is a schematic diagram showing the power arrangement and the ray trajectory of the optical system including the two lenses of the first embodiment. FIG. 10 shows the arrangement on the narrow angle side. The illustration on the wide-angle side is omitted.

  The lens 3 and the lens 4 are considered as thin lenses having a thickness of zero, and the respective focal lengths are assumed to be f1 and f2. The distance between the lens 3 and the lens 4 is d, and the distance from the light emitting surface of the COB 1 to the lens 3 is s. The solid line in the figure represents the locus of light emitted from the emission center of COB 1, that is, a point on the optical axis Z. On the other hand, the broken line represents the locus of light emitted parallel to the optical axis Z from the position of D / 2, where D is the diameter of the end of COB1, that is, the light emitting surface.

  As described above, it is difficult to obtain a light distribution on the narrow angle side for narrowing the beam, particularly in a chip-on-board LED having a large light emitting surface. If the light distribution on the narrow angle side is obtained, the distance d between the lens 3 and the lens 4 is reduced on the wide angle side, except for the case of C3> C4 as in the second comparative example described above, so that the lens 4 becomes the lens 3. It is often obtained naturally by moving closer. From FIG. 10, when the lens 4 is brought closer to the lens 3, both the solid line light beam and the broken line light beam have an angle in a direction that further spreads with respect to the optical axis Z after being emitted from the lens 4.

  In order to narrow the beam and improve the light utilization efficiency and obtain a high front luminous intensity, it is preferable that the light emitted from one point of the COB 1 represented by the solid line is made substantially parallel by the lens 3 and the lens 4. . That is, the light emitted from the emission center of the COB 1 is preferably substantially parallel to the optical axis Z after passing through the lens 4.

  And the light emitted in parallel to the optical axis Z from the end of COB1 represented by the broken line (because COB1 is a completely diffusive light distribution, its front direction, the direction parallel to the optical axis Z has the highest luminous intensity) After passing through the lens 3, it once intersects with the optical axis Z before entering the lens 4, and after passing through the lens 4, it is emitted in the direction of approximately θ / 2 of the beam divergence angle θ with respect to the optical axis Z. It is good to be.

  As described above, in FIG. 10, f1 <f2, but if f1≈f2 etc. and the broken light beam does not cross the optical axis Z before passing through the lens 3, the broken light beam passes through the lens 4. The emission direction has a large angle with respect to the optical axis Z, and a narrow-angle light distribution cannot be obtained.

When trying to satisfy the above conditions, the following equation holds. In (Expression 3), the combined power of the lens 3 and the lens 4 is Φ, and the power of the lens 4 is Φ2. The power Φ is the reciprocal of the focal length f.
θ / 2 = Φ × D / 2
s × Φ = 1−d × Φ2 (Formula 3)
By transforming (Expression 3), the following (Expression 4) is obtained.
f1 = (s × (f2-d)) / (f2-s-d)
f2 = d / (1−s × θ / D) (Formula 4)

  As described above, f1 <f2 clearly from FIG. 10, but the approximate ratio of f1 and f2 will be described below. The relational expression between f1 and f2 is (Formula 4) above, and the range of each parameter is described below.

  First, since the lens 3 is disposed close to the COB 1, s is set to about 0.1 to 3 [mm]. In (Expression 4), since s = 0 [mm] cannot be calculated, it is assumed from 0.1 [mm] for convenience. Since the beam divergence angle θ depends on whether the distribution shape of the light distribution is a top hat (rectangular) type or a Gaussian (normal distribution) type, it is approximately 0.175 to 0.349 [rad] (10 ~ 20 [deg]). The diameter D of the light emitting surface of COB1 is assumed to be approximately φ9 to 13 [mm].

  Since the distance d between the remaining lens 3 and lens 4 is undetermined, f1 is determined first, and then d and f2 are obtained. The main purpose of the lens 3 is to make the light emitted from the COB 1 enter the lens 4 with high aperture efficiency and to obtain high front luminous intensity and light utilization efficiency. For this reason, the shorter the focal length f1 of the lens 3, the better, and the power of the lens 3 is dominated by the S2 surface from C1 <C2, so the smaller the radius of curvature of the S2 surface, the better. It will be. However, in practice, as shown in FIG. 11, when the radius of curvature is smaller than the radius D / 2 of COB1, the lens 3 becomes smaller than COB1, and light emitted from the peripheral portion of COB1 cannot be collected. Even when the curvature radius of the S2 surface is exactly D / 2, it is difficult to hold the lens 3 or the like. Therefore, it is assumed that the curvature radius R2 of the S2 surface is D / 2 to D, and the refractive index n of the lens 3 is about 1.5, so that f1 takes a value of about D to 2D.

The parameters described above are as follows.
f1: Focal length of lens 3 = greater than D and 2D or less f2: Focal length of lens 4 d: Distance between lens 3 and lens 4 s: Distance from light emitting surface of COB1 to lens 3 = 0.1 to 3.0 [Mm]
D: Diameter of light emitting surface of COB1 = φ9 to φ13 [mm]
θ: Beam divergence angle = 0.175 or more and 0.349 or less [rad] (10 or more and 20 or less [deg])
Φ: Combined power of lens 3 and lens 4 = Φ1 + Φ2-d × Φ1 × Φ2
Φ1: Lens 3 power = 1 / f1
Φ2: Power of lens 4 = 1 / f2
R2: radius of curvature of S2 surface = D / 2 or more and D or less n: refractive index of lens 3 and lens 4 = about 1.5

  FIG. 12 shows the relationship between the focal length f1 of the lens 3 and the focal length f2 of the lens 4 derived from (Equation 4) by setting the parameters as described above. The horizontal axis is f1 / D (that is, takes a value of 1 to 2), and the vertical axis is f2 / f1.

FIG. 12 shows that f2 becomes shorter as f1 becomes longer.
As shown in FIG. 11, when f1 is equal to D, that is, when f1 / D = 1, it is difficult to hold the lens 3, and it is possible to enter the lens 3 out of the light emitted from the peripheral part of the COB1. In addition, since there is a part where light spills in the peripheral portion, f1 / D = 1 is difficult to adopt, and f1 / D> 1.0 is desirable. In the case of f1 / D> 1.0, the approximate ratio of f1 and f2 for narrowing the beam and improving the light utilization efficiency and obtaining high front luminous intensity is as follows.
When f1 / D = 1.25 to 2.0, f2 / f1 is 1.5 to 6.8.
In the case of f1 / D = 1.50-2.0, f2 / f1 is 1.5-5.0.
When f1 / D = 2.0, f2 / f1 is 1.5 to 3.5.
Considering holding of the lens 3 and light spillage in the peripheral portion, it is preferable that f1 / D = 1.50 or more, and f2 / f1 is a suitable ratio of about 1.5 to 5.0.

Further, the power of the lens 3 is substantially controlled by the S2 surface, the power of the lens 4 is substantially controlled by the S4 surface, and the refractive index n of the lens 3 and the lens 4 is about 1.5. f1≈2 / C2 and f2≈2 / C4. Therefore, the following relationship is established between C2 and C4.
C2 / C4 = 1.5 to 5.0 (Formula 5)

Further, FIG. 12 shows the following.
1. The smaller the distance s from the light emitting surface of the COB 1 to the lens 3 is, the smaller f2 / f1 is.
2. The larger the beam divergence angle θ, the smaller f2 / f1.
3. The larger f1 / D is, the smaller f2 / f1 is.

  As described above, the LED illumination device according to the first embodiment is an LED illumination device including two transparent lenses in front of the LED, and the lens 3 (first lens) is placed close to the LED. The lens 4 (second lens) is disposed farther from the LED than the lens 3 (first lens), and the lens 4 (second lens) is movable in the optical axis direction. The distance from the first lens) is adjustable, the approximate curvature of the LED side surface of the lens 3 (first lens) is C1, the approximate curvature of the light output surface is C2, and the lens 4 (second lens). When the approximate curvature of the LED side surface of the lens) is C3 and the approximate curvature of the light exit side surface is C4, the relationship of C1 <C2 and C3 <C4 is satisfied.

  In the LED lighting device according to the first embodiment, high front luminous intensity and high light utilization efficiency can be obtained by the lens 3 (first lens) arranged in proximity. Due to the lens 4 (second lens) having the convex surface facing the emission side, no void occurs.

  The LED illumination device according to the first embodiment has an effect that light distribution with an arbitrary beam divergence angle from a narrow angle to a wide angle can be obtained with high front luminous intensity and high light utilization efficiency even in a COB having a large light emitting surface. .

Embodiment 2. FIG.
FIG. 7 is a side sectional view of the illumination device 10 according to Embodiment 2 of the present invention. FIG. 7A is a cross-sectional view showing a lens arrangement on the narrow angle side, and FIG. 7B is a cross-sectional view showing a lens arrangement on the wide angle side.
In the second embodiment, the thick lens 4 in the illumination device 10 according to the first embodiment is formed into a Fresnel lens. Hereinafter, only differences from the first embodiment will be described.

When the lens 4 is manufactured by injection molding a transparent resin such as acrylic or polycarbonate, there is a problem that sink marks occur in the thick lens and the molding time is long. Therefore, these problems can be solved by making the Fresnel lens thin and uniform.
When the lens 4 is made into a Fresnel lens, the S4 surface having a larger curvature is the Fresnel surface. If the Fresnel surface is approximated by a spherical surface, the curvature becomes moderate. Naturally, C1 to C4 in the above (Equation 1) eliminates the step of the Fresnel surface and indicates the curvature in a state where the Fresnel surface is not formed. Also in the Fresnel lens of the second embodiment, the relationship of (Expression 1) and (Expression 5) is established. In the second embodiment, the surface S3 is substantially planarized with C3 = 0 for another purpose to be described later.

  Further, when the lens 4 is a Fresnel lens, the Fresnel surface is the outermost surface of the lighting device 10, and thus cracking may occur due to the valley portion 4 </ b> V of the Fresnel surface when cleaning with alcohol or the like. In order to prevent this crack, it is necessary to provide the valley portion 4V with a fillet surface having a radius of curvature of 0.2 [mm] or more. Moreover, since the peak portion 4P becomes a valley in the mold, the curvature of the tip of the cutting tool for processing the mold remains. Unlike the controlled light beam that passes through the original lens surface, the light beam that passes through the valley portion 4V and the mountain portion 4P is randomly scattered in various directions. The more these rays are, the lower the front luminous intensity and light utilization efficiency. For this reason, in each annular zone of the Fresnel surface, the height H of the Fresnel lens surface is set to be the curvature of the valley portion 4V and the mountain portion 4P so that the ratio of the valley portion 4V and the mountain portion 4P is reduced. It is desirable to make it sufficiently higher than the radius, and it is preferable to set it to 2 [mm] or more. For example, the height H of the Fresnel lens surface is desirably 5 times or more higher than the curvature radius of the valley portion 4V or the mountain portion 4P, preferably 10 times or more.

  In the second embodiment, as shown in FIG. 9A, the back surface of the Fresnel surface of the lens 4, that is, the S3 surface, and the direction of two axes orthogonal to each other at a pitch of 3 mm or less with a small spherical lens. The fly-eye lenses are arranged in a square lattice pattern. The height of each spherical lens is equal and is about 0.1 to 0.2 [mm]. The fly-eye lens is a means for preventing the phenomenon that the image of the chip in the COB 1 is projected onto the irradiated surface.

  FIG. 8A shows the color of the irradiated surface in the illumination device 10 according to the first embodiment. The distance from the illumination device 10 to the irradiated surface was 1 [m], the beam divergence angle was about 20 [deg], and the size of the irradiated surface was 0.5 [m] square. In the figure, the area shown in white is the area that appears to be slightly bluish white from pseudo white, and the area shown in gray is the area that appears slightly yellow, and the darker the gray, the stronger the yellow. ing. From FIG. 8A, it can be seen that the image of the chip (white portion of the central portion) can be clearly seen in the central portion of the irradiated surface.

On the other hand, FIG. 8B shows the color of the irradiated surface in the illumination device 10 using the fly-eye lens according to the second embodiment. Each condition such as the distance from the illumination device 10 to the irradiated surface is the same as in FIG. It can be seen that the chip image at the center of the irradiated surface disappears and color unevenness is suppressed.
As described above, the fly-eye lens having the surface S3 diffuses light passing through the lens 4 weakly, thereby preventing the image of the chip in the COB 1 from being projected onto the irradiated surface.

  Note that the S3 surface only needs to be able to weakly diffuse the light passing through the lens 4, so that small spherical lenses are not arranged in a square lattice pattern in the directions of two axes perpendicular to each other, but as shown in FIG. They may be arranged in a hexagonal lattice shape, that is, in a honeycomb shape, in the directions of three axes having an angle of 60 [deg].

  Alternatively, instead of a small spherical lens, as shown in FIG. 9C, for example, a lens array in which donut surfaces that are sequentially different at a pitch of 3 [mm] or less are arranged concentrically in multiple layers. good. In this case, the mold nesting corresponding to the lens surface of the S3 surface can be processed with a general NC lathe.

  Furthermore, instead of applying such shapes, the S3 surface may be simply flattened and the surface skin may be roughened by sandblasting.

  When a chip-on-board type LED is used for a spotlight, a yellow ring may be generated around a bright white irradiation region on the irradiated surface. It can be seen that the above-described occurrence also occurs in FIGS. 8A and 8B. In FIG. 7, a diaphragm 7 indicated by a broken line on the exit side of the lens 4 is a member that shields this yellow ring and suppresses the generation. Similarly to the fixed cylinder 5 and the movable cell 6, the diaphragm 7 is also a die-cast or plastic molded product such as aluminum or magnesium. After all, it is preferable to dye black.

  FIG. 8B shows the color of the irradiated surface when the diaphragm 7 is not arranged. FIG. 8C shows the color of the irradiated surface in the illumination device 10 according to the second embodiment when the diaphragm 7 is arranged. It can be seen that the yellow ring disappeared by the diaphragm 7 and the uneven color of the irradiated surface was further suppressed.

  That is, according to the illumination device 10 according to the second embodiment, the thick lens 4 is made into a Fresnel lens so as to be thin and uniform, thereby shortening the molding time, preventing the occurrence of sink marks, and being inexpensive and stable. Can be manufactured.

  Further, by providing a fly-eye lens on the back side of the Fresnel surface of the lens 4, the image of the chip in the COB 1 projected on the irradiated surface is eliminated, and color unevenness can be suppressed.

  Further, the diaphragm 7 disposed on the exit side of the lens 4 can prevent a yellow ring from being generated on the irradiated surface, and can further suppress color unevenness.

  As described above, in addition to the configuration of the LED lighting device of the first embodiment, the LED lighting device of the second embodiment has a Fresnel lens on the light output side surface of the lens 4 (second lens). It is characterized by. For this reason, when the lens 4 (second lens) is thin and uniform, the lens 4 (second lens) can be injection-molded stably at low cost.

  Further, the lens height in each annular zone of the Fresnel lens is 2 [mm] or more. For this reason, the fall of the utilization efficiency of the light accompanying Fresnel lens conversion can be suppressed.

  Alternatively, in the LED lighting device of the second embodiment, the surface of the lens 4 (second lens) on the LED side is a lens array in which small spherical lenses are arranged in a square lattice or a hexagonal lattice. It is characterized by. For this reason, it can suppress that the image of the chip | tip in COB1 is projected on a to-be-irradiated surface.

  Alternatively, in the LED illumination device of the second embodiment, the lens side of the lens 4 (second lens) is a lens array in which donut surfaces having different diameters are arranged in multiple layers concentrically. It is characterized by that. For this reason, it can suppress that the image of the chip | tip in COB1 is projected on a to-be-irradiated surface.

  Furthermore, the LED lighting device of the second embodiment is characterized in that a diaphragm is provided on the light output side of the lens 4 (second lens). For this reason, generation | occurrence | production of the yellow ring in a to-be-irradiated surface can be suppressed.

  In Embodiments 1 and 2, the COB 1 is used as the light source. However, instead of the COB method, LEDs arranged in an array may be used as the light source. Moreover, it may not be LED. Further, the LED arrangement may not be circular, but may be polygonal.

  DESCRIPTION OF SYMBOLS 1 COB, 2 board | substrate, 3 lens, 4 lens, 4P The part of the peak of a Fresnel surface, 4V The part of the valley of a Fresnel surface, 5 Fixed cylinder, 6 Movable cell, 7 Diaphragm, 10 Illumination device.

Claims (10)

The first lens,
A second lens,
A light source is attached, and the first lens is arranged in the light output direction of the light from the light source, and further includes a fixed cylinder for arranging the second lens,
The approximate curvature of the surface on the light source side of the first lens is C1,
The approximate curvature of the light exit side surface of the first lens is C2,
The approximate curvature of the surface on the light source side of the second lens is C3,
When the approximate curvature of the light exit side surface of the second lens is C4,
C1 <C2 and C3 <C4
A lighting device characterized by the above.   The relationship between the approximate curvature C2 of the light output side surface of the first lens and the approximate curvature C4 of the light output side surface of the second lens is C2 / C4 = 1.5 to 5.0. The lighting device according to claim 1. 3. The illumination device according to claim 1, wherein the focal length f1 of the first lens and the focal length f2 of the second lens have the following relationship.
f1 = (s × (f2-d)) / (f2-s-d)
f2 = d / (1-s × θ / D)
f1: Focal length of the first lens f2: Focal length of the second lens d: Distance between the first lens and the second lens s: Distance from the light emitting surface of the light source to the first lens D: Light emission of the light source Surface diameter θ: Beam divergence angle   The lighting device according to claim 1, wherein the light source is a chip-on-board (COB) type LED.   The illumination device according to claim 1, wherein the fixed cylinder includes a movable cell that changes a distance between the first lens and the second lens.   The lighting device according to claim 1, wherein a surface on the light output side of the second lens is formed as a Fresnel lens.   The lighting device according to claim 6, wherein a lens height in each annular zone of the Fresnel lens is 2 mm or more.   The illumination device according to any one of claims 1 to 7, wherein a surface of the second lens on the light source side is a lens array in which small spherical lenses are arranged in a square lattice shape or a hexagonal lattice shape.   The illumination device according to any one of claims 1 to 7, wherein the light source side surface of the second lens is a lens array in which donut surfaces having different diameters are arranged concentrically in multiple layers. .   The illumination device according to claim 1, further comprising a diaphragm on a light output side of the second lens.