JP2012123371A - Concave lens, optical member and illumination device using these - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concave lens and an illumination device using the same with small energy consumption such as an LED and capable of having a display section of a great area irradiated at almost uniform distribution of illuminance over a wide range by effectively using light energy with high directivity.SOLUTION: The concave lens is characterized by having numerous triangular shaped protrusions 16a, 16b, 16c, 16d... with the same height h as a section in the radial direction going through the center formed in the radial direction on one surface of a transparent substrate 14 transmitting light.

Description

  The present invention relates to, for example, a concave lens and an optical member suitable for converting light from a point light source into light having a large area planar intensity distribution, and an illumination device using these.

  Lasers, light emitting diodes (LEDs), and the like are light sources with high directivity, and thus cannot achieve a luminous intensity distribution having a wide light distribution like a light bulb or a fluorescent lamp. For this reason, in order to use an LED or the like as a next-generation light source that replaces a light bulb or a fluorescent lamp, it is necessary to arrange a large number of LEDs, for example, to spread light in a planar shape with a substantially uniform intensity.

  In order to simply spread the light from the light source, conventionally thin light diffusing elements such as diffusing plates and diffusing films, or convex lenses (including bullet-type LED lenses) and concave lenses that use light refraction are made thinner. Fresnel lenses and kinoforms that have been used have been used.

  However, the optical component taken up above is not only an element intended for light distribution control of a point light source, but also has the following problems. That is, for example, if light is diffused by the diffusion plate, the transmittance is deteriorated and the light use efficiency is deteriorated. Moreover, as shown in FIG. 11, since the concave lens 2 is a lens using refraction, its focal length depends on the refractive index and the radius of curvature of the substrate material, and the focal length can be freely controlled. I can't. Furthermore, there is a problem that the lens shape cannot be reduced.

  In view of such a conventional situation, the present invention uses a light energy with low energy consumption and high directivity, such as an LED, so that a large-area display unit can be in a high range with a substantially uniform illuminance distribution. An object of the present invention is to provide a concave lens and an optical member that can irradiate, and an illumination device using these.

  The present inventors have found a technique having high transparency and easy control of the focal length in order to spread and extract as much light as possible to the outside, and have completed the present invention.

  In order to achieve the above object, a concave lens according to the present invention forms a plurality of concentric structures on a surface of a transparent base material that transmits light, and a plurality of structures having a triangular cross section passing through the center. It is characterized by that.

In the concave lens according to the present invention, the triangular structure may exist between an m-th zone radius that satisfies the following expression (1) and an m-1 zone radius. preferable.
m-th zone radius (μm): r _(m) = (m ² λ ₀ ² + 2mλ ₀ f) ^1/2 (1)
(M represents an arbitrary integer of 1 or more, f represents an arbitrary number of focal lengths (μm), and λ ₀ represents an arbitrary number of light source wavelengths (μm).)

Furthermore, in the concave lens according to the present invention, it is preferable that all the heights of the triangular structures are represented by the following formula (2).
Height (μm): h = λ ₀ / (n−1) (2)
(Λ ₀ represents an arbitrary number of light source wavelengths (μm), and n represents a refractive index with respect to λ ₀ of the substance forming the structure.)

  The optical member according to the present invention is characterized in that a plurality of structures having a rectangular cross section are formed on at least one surface of a transparent base material that transmits light.

  Furthermore, in the optical member according to the present invention, it is preferable that the rectangular structure is formed concentrically.

In the optical member according to the present invention, at least one rectangular structure is present between the m-th zone radius and the m-1-th zone radius satisfying the following formula (1). It is preferable to be a group.
m-th zone radius (μm): r _(m) = (m ² λ ₀ ² + 2mλ ₀ f) ^1/2 (1)
(M represents an arbitrary integer of 1 or more, f represents an arbitrary number of focal lengths (μm), and λ ₀ represents an arbitrary number of light source wavelengths (μm).)

  Furthermore, in the optical member according to the present invention, it is preferable that the height T of the rectangular structure is 0.4 μm ≦ T ≦ 1.2 μm.

In the optical member according to the present invention, it is preferable that the rectangular structure is a group of structures that satisfy the following conditions 1) to 5).
1) Width of group of m-th structure (μm): d _m = r _(m) −r _(m−1)
2) Width obtained by dividing the width of the m-th structure into an arbitrary number (μm):
g _m = d _m / x _m
(X _m represents an arbitrary integer of 1 or more in the m-th structure.)
3) i-th height (μm) at a position corresponding to the m-th structure:
_{T m (i) = {T} / (x m -1)} · (i-1)
(T represents the height of the rectangular structure, and i represents an integer of 1 to x _m .)
4) Duty ratio of the i-th structure existing in the group of the m-th structure:
t _{m (i)} = 1−T _{m (i)} / T
5) Width of the i-th structure existing in the group of the m-th structure: t _{m (i)} · g _m

  With a concave lens or optical member having such a configuration, a thin lens has high transparency, easy control of the focal length, and low cost in spreading the illumination intensity with respect to a large area to be substantially uniform. Can be formed.

  In addition, an illumination device according to the present invention includes any one of the concave lenses or optical members described above and a light source.

In the illumination device according to the present invention, the light source is preferably a white LED.
In the lighting device according to the present invention, the light source wavelength λ ₀ is preferably designed to be 0.555 ± 0.020 μm.
Moreover, in the illuminating device which concerns on this invention, it is preferable that the focal distance f is 0.3-0.1 mm.

  If it is an illuminating device of such a structure, effective use can be aimed at as illuminating devices, such as a signboard mounted in a shop front etc., for example.

  According to the present invention, it is possible to convert light from a highly directional point light source into light having a substantially uniform intensity and a large area planar intensity distribution, the focal length can be controlled by the structure, and easy by electron beam drawing. Can be produced. Furthermore, if the lens-shaped mold of the present invention is manufactured and injection molding becomes possible, it can be manufactured at low cost, and irradiation can be performed with substantially uniform illuminance for a large area.

FIG. 1 is a schematic cross-sectional view of a lighting device using a concave lens according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view in the case where the lighting device is used by being incorporated in a store signboard or the like. FIG. 3 is an apparatus diagram of a far-field image for examining how much spread is shown by irradiating a laser beam from a slit toward a wall. 4A, 4 </ b> B, and 4 </ b> C are an initial state of the concave lens shown in FIG. 1, a state in which a convex portion having a triangular cross section is approximated to a stepped convex portion, and a stepped shape. It is explanatory drawing which showed the state which converted the convex part into binarization corresponding to duty ratio. FIGS. 5A and 5B illustrate, for example, a comparison between a state before binarization of the concave lens having a convex section having a triangular cross section shown in FIG. 1 and a state after binarization. FIG. FIG. 6 is a conceptual diagram showing optimization of the number of protrusions according to the periodic position of the diffractive optical member. FIG. 7 is a diagram showing the results of first-order diffracted light intensity measurement using a photodiode of a diffractive optical member and a structure-modulated diffractive optical member with the number N of protrusions per cycle. FIG. 8 is a diagram showing the diffusion of light of the LED when the designed light source wavelength is changed. FIG. 9 shows the measurement of the spatial distribution of chromaticity when the design light source wavelength is changed, and the chromaticity deviations from x = 0.310 and y = 0.316 on the chromaticity coordinates are standard. It is a figure shown as a deviation. FIG. 10 is a diagram illustrating the diffusion of light from the LED when the focal length is changed. FIG. 11 is a cross-sectional view showing a light refraction state by a conventional concave lens.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view of an illumination device 12 using a concave lens 10 according to an embodiment of the present invention.

The concave lens 10 is a Fresnel-type concave lens, and has convex portions 16a, 16b, 16c having a constant height h on one surface of a transparent base plate 14 that is light-transmitting and formed in a flat plate shape. 16d... In the radial direction. The vertical surface 13 forming one side of the triangle of each of the convex portions 16a, 16b, 16c, 16d,... Has a structure that is disposed on the outer side in the radial direction. That is, the triangular slope is inclined outward. Further, in the concave lens 10, the gaps r ₁ , r ₂ , r ₃ , r ₄ between the convex portions are set to be reduced at a predetermined ratio as approaching the outer side in the radial direction.

  In the case of the illuminating device 12 in which the concave lens 10 and the light source 18 formed in this way are combined, when light is irradiated from the light source 18 in the arrow Y direction, the light is structured when the transparent base material 14 is emitted. Since light is diffracted toward the thicker direction, the light spreads in the y direction. Thereby, even if it is the point light source 18, it becomes possible to irradiate a large area. At this time, the light intensity can be made substantially uniform on the exit surface side by the light diffraction phenomenon, so that the spread of the light can be obtained.

Such an illuminating device 12 can be used, for example, as a signboard illumination of a convenience store as shown in FIG.
As shown in FIG. 2, in the signboard illumination 20, for example, the illumination device 12 is accommodated in a plastic housing 22. And in this illuminating device 12, the highly directional light irradiated from the LED lamp 18 is reflected to the opening surface side by the reflector 26, and the light is diverged over a wide range by the concave lens 10, so that milky white Information described on the plate 28 is displayed outward.

  With such ease of use, it is possible to irradiate a large display area with a substantially uniform illuminance distribution by effectively using LED or laser energy with low energy consumption and high directivity, and continuous use over a long period of time Can be operated at low cost.

In the illumination device 20 shown in FIG. 2, the distance E from the top plate of the reflector 26 to the lower surface of the plate body 28 is 6 cm, and the width F of the housing 22 is 20 cm.
Thus, even if the distance between the LED lamp 18 and the illumination plate 28 that emits light is a short distance, the light can be illuminated substantially uniformly outward.

Note that the light source is not limited to the LED lamp 18 and the laser, and the same effect can be obtained even if the light source is an organic EL, a light bulb, a fluorescent lamp, or the like.
The transparent base material 14 constituting the concave lens 10 is not particularly limited as long as it is a transparent organic polymer. Typically, any polymer film made of a cyclic olefin resin, a polycarbonate resin, an acrylic resin, a polyester resin, a polysulfone resin, or the like having high transparency can be used. It is also possible to use a blend of two or more resins. Among these resins, cyclic olefin resins are preferable from the viewpoint of optical properties and heat resistance.

In order to investigate the effect when the concave lens 10 is used for a lighting device for a signboard, an indoor experiment was conducted. In this experiment, as shown in FIG. 3, a monochromatic (green) laser having a light source wavelength of 532 nm was used as the light source 18. Then, a laser beam was irradiated toward the wall 21 that was 20 cm away from the pinhole 19 having a diameter of 1 mm, and it was confirmed how much spread was exhibited in the width direction. It was confirmed that the light spread S was 10 cm, and it was confirmed that the light spreads sufficiently.
Below, when using the concave lens 10 as the illuminating device 12 for signboards shown in FIG. 2, a preferable aspect is demonstrated, referring FIG.

  In the example shown in FIG. 4, for example, the convex portion 16a formed in the center of the concave lens 10, for example, is divided into a plurality of regions (2, 4, 6) and binarized to obtain an equivalent product. The design stages to get are shown in order.

  FIG. 4A shows a concave lens according to an embodiment of the present invention. This concave lens is a concentric structure on one surface of the transparent substrate 14, and a plurality of structures 16a, 16b,.

The triangular structure exists between an m-th zone radius that satisfies the following formula (1) and an m-1 zone radius.
m-th zone radius (μm): r _(m) = (m ² λ ₀ ² + 2mλ ₀ f) ^1/2 (1)
(M represents an arbitrary integer of 1 or more, f represents an arbitrary number of focal lengths (μm), and λ ₀ represents an arbitrary number of light source wavelengths (μm).)

Further, the height h of the triangular structures 16a, 16b... 16m in the concave lens shown in FIG. 4A has a height (μm) represented by the following formula (2).
Height (μm): h = λ ₀ / (n−1) (2)
(N represents the refractive index with respect to λ ₀ of the substance forming the structure.)
With a serrated concave lens having such an annular radius and height, it is possible to obtain light spreading with light having high directivity and light intensity substantially uniform on the exit surface side.

  Therefore, the sawtooth concave lens shown in FIG. 4A and the light source 18 are combined to form an illuminating device, and the illuminating device can be preferably used in the illumination signboard 20 as shown in FIG.

  Furthermore, in the present invention, a binary type diffractive optical member as shown in FIG. 4C is produced based on the concave lens shown in FIG. 4A, and the same function as the concave lens can be obtained. it can.

  Here, in the present invention, in order to process the surface of the flat transparent substrate 14, for example, a photolithography and dry etching technique that is generally used for LSI manufacturing, or a mold is pressed into an ultraviolet curable resin. Technology is adopted.

  When producing by photolithography and dry etching technology, specifically, a photoresist is spin-coated on a transparent substrate, and exposure / development is performed with UV light through a photomask to transfer the fine structure pattern to the photoresist. To do. Then, the substrate is etched to a depth corresponding to radians by dry etching, the fine structure is transferred to the substrate, and finally the resist is removed, as shown in FIG. A cross-sectional shape having is completed.

  When a binary diffractive optical member as shown in FIG. 4C or FIG. 5B is finally produced from the concave lens of FIG. 4A, the following conditions are used.

That is, it is further set to satisfy the conditions 1) to 5).
1) Width of group of m-th structure (μm): d _m = r _(m) −r _(m−1)
2) Width obtained by dividing the width of the m-th structure into an arbitrary number (μm): g _m = d _m / x _m
(X _m represents an arbitrary integer of 1 or more in the m-th structure.)
3) i-th height (μm) at a position corresponding to the m-th structure:
_{T m (i) = {T} / (x m -1)} · (i-1)
(I is an integer of 1 to x _m.
T is the height of the structure, and 0.4 μm ≦ T ≦ 1.2 μm. )
4) Duty ratio of the i-th structure existing in the group of the m-th structure:
t _{m (i)} = 1−T _{m (i)} / T
5) Width of the i-th structure existing in the group of the m-th structure: t _{m (i)} · g _m
(M represents an arbitrary integer of 1 or more, f represents an arbitrary number of focal lengths (μm),
λ ₀ is an arbitrary number and represents the light source wavelength (μm). )

Under the above conditions, the convex portion 16a and the like are divided into a plurality of regions. The number of divisions is arbitrary, but is preferably an even number such as 2, 4, 6.
By applying the above conditions, for example, the width g _m when the width d _m of the group of m-th structure was divided into four is g _m = d _m / 4. The height T _{m (i)} at this time is T _{m (i)} = {T / (x _m −1)} · (i−1) from the above 3).
T _{m (1)} = 0
T _{m (2)} = T / 3
T _{m (3)} = 2T / 3
T _{m (4)} = T
Thus, the height of the group of structures (J, K, L, M) toward the center gradually decreases toward the center, and the height of the structure M is zero.

Further, the duty ratio at this time is t _{m (i)} = 1−T _{m (i)} / T from the above 4).
t _{m (1)} = 1
t _{m (2)} = 2/3
t _{m (3)} = 1/3
t _{m (4)} = 0
It becomes.

Note that the i-th height T _{m (i)} described in the above 3) is, for example, the depth W _i of the protrusion as shown in FIG. 4B.
Thus, as shown in FIG. 4 (C), each width of the structure (O, P, Q, R), from the 5), as demonstrated by the _{t m (i) · g m} , t 1 , T ₂ , t _3, and narrower toward the center, and t ₄ has a width of zero.

That is, when the width of the structure O is 1, the structure P has a ratio of 2/3, the structure Q has a ratio of 1/3, and the structure R has zero.
FIGS. 5A and 5B show an example in which binarization is performed from the sawtooth projections 16a, 16b,...

  As shown in FIG. 5B, in the diffractive optical member 40, the period d becomes shorter toward the outside.

[Example 1]
FIG. 6 is a structural diagram of the right half of the diffractive optical member with the number of protrusions per cycle N = 2 (the above formula 2), x _m = 4). The produced diffractive optical member 50 was irradiated with laser light (diode-excited green solid laser, manufactured by PROPHOTNIX, λ = 0.532 μm), and the focal length was confirmed from the far-field image and light intensity measurement.

  In addition, in order to investigate the relationship between the number N of protrusions per period and the intensity of diffracted light, a diffraction pattern having a periodic structure of the center, middle, and edge portions of each diffractive optical member is prepared, and the first-order diffracted light Intensity measurements were taken.

From this result, in the center structure which is the central portion of the diffractive optical member, when the number of protrusions per period N = 4 (x _m = 6 in the above equation 2), the intermediate region of the diffractive optical member In the middle structure, where N = 2 (in the above formula 2), x _m = 4), in the edge structure near the outside of the diffractive optical member, in the N = 1 (the above formula 2), x _m = In the case of 2), a strong first-order diffracted light intensity was obtained.

  From this result, it is assumed that the first period (center structure) is N = 4, the second period to the 36th period is N = 2, and the 37th period to the 109th period is N = 1. A member was prepared.

  Using the structural modulation type diffractive optical member thus fabricated, the light intensity of the far-field image was measured with a photodiode. As a result, as shown in FIG. 7, by producing a structure-modulating diffractive optical member having different numbers of protrusions per period in the center, middle, and edge portions, N = 1 diffraction type in all periods The most preferable illuminance distribution was obtained as compared with the case where the optical member was produced.

[Example 2]
When the emission peak of a surface mount type LED (GOLDEN DRAGON ULTRA WHITE, LUW W5SM-JZKY-4C8E, manufactured by OSRAM) was measured with an LED light distribution meter (IMS-5000, manufactured by Asahi Spectroscopy), the emission spectrum was It spreads between 0.380 and 0.800 μm, and the peak was a blue LED peak 0.446 μm and a YAG phosphor peak 0.555 μm.

  The light source wavelength is designed to be 0.446 μm, 0.500 μm, 0.555 μm, 0.780 μm, the number N of protrusions per cycle is N = 1 in all cycles, the focal length is 2 mm, and the diameter A 1 mm diffractive optical member was produced.

  A 1 mm diameter pinhole was attached to the LED, the diffractive optical member produced above was mounted on the LED, and the light intensity distribution was measured with a photodiode at a distance of 30 mm from the diffractive optical member. As a result, as shown in FIG. 8, even when the diffractive optical member is designed for any light source wavelength, the diffractive optical member is mounted as compared with the case where the diffractive optical member is not mounted (only the pinhole). It was found that the light from the LED was diffused.

[Example 3]
Instead of the photodiode of Example 2, a screen was installed at a position 0.7 m from the diffractive optical member, and an image projected on the screen was taken. In addition, the spatial distribution of chromaticity is measured with an LED light distribution meter (IMS-5000, manufactured by Asahi Spectroscopy Co., Ltd.), and the color from x = 0.310 and y = 0.316 on the chromaticity coordinates. The degree deviation was calculated as the standard deviation.

As a result, as the diffractive optical member is designed with a light source wavelength of 0.446 μm to 0.555 μm, the color changes from blue to white, and redness increases for the diffractive optical member designed with a light source wavelength of 0.780 μm. I knew it would come. Further, as shown in FIG. 9, it was found that the standard deviation of the diffractive optical member designed with the light source wavelength of 0.555 μm is the smallest over a wide angle range. Thus, in one embodiment of the lighting device according to the present invention, the light source wavelength λ ₀ is designed to be 0.555 ± 0.020 μm, that is, 0.555−0.020 μm ≦ λ ₀ ≦ 0.555 + 0.020 μm. It is preferable that

[Example 4]
A diffractive optical member was prepared in the same manner as in Example 2 except that the light source wavelength was designed to be 0.555 μm and the focal length was set to 0.3 mm, and the same measurement as in Example 2 was performed. As a result, as shown in FIG. 10, even when the focal length is 0.3 mm, the LED light is more light when the diffractive optical member is mounted than when the diffractive optical member is not mounted (only the pinhole). I found that it was spreading. Thus, in one embodiment of the lighting device according to the present invention, the focal length f is preferably 0.3 to 0.1 mm.

DESCRIPTION OF SYMBOLS 10 Concave lens 12 Illumination device 13 Wall surface 16 Transparent base material 16a, 16b, 16c, 16d Projection body 18 Light source (532 nm green laser)
19 Pinhole 20 Signboard 21 Wall 22 Case 26 Reflector

Claims (12)

  A concave lens, wherein a plurality of concentric structures having a triangular cross section passing through the center are formed on at least one surface of a transparent substrate that transmits light. 2. The concave lens according to claim 1, wherein the triangular structure exists between an m-th annular zone radius satisfying the following formula (1) and an m−1-th annular zone radius. .
m-th zone radius (μm): r _(m) = (m ² λ ₀ ² + 2mλ ₀ f) ^1/2 (1)
(M represents an arbitrary integer of 1 or more, f represents an arbitrary number of focal lengths (μm), and λ ₀ represents an arbitrary number of light source wavelengths (μm).) 3. The concave lens according to claim 1, wherein all the heights of the triangular structures are represented by the following formula (2): 3.
Height (μm): h = λ ₀ / (n−1) (2)
(Λ ₀ represents an arbitrary number of light source wavelengths (μm), and n represents a refractive index with respect to λ ₀ of the substance forming the structure.)   An optical member, wherein a plurality of structures having a rectangular cross section are formed on at least one surface of a transparent substrate that transmits light.   The optical member according to claim 4, wherein the rectangular structure is formed concentrically. The said rectangular structure is a group which exists in one or more between the mth ring zone radius which satisfy | fills following formula (1), and the m-1st ring zone radius, It is characterized by the above-mentioned. 4. The optical member according to 4 or 5.
m-th zone radius (μm): r _(m) = (m ² λ ₀ ² + 2mλ ₀ f) ^1/2 (1)
(M represents an arbitrary integer of 1 or more, f represents an arbitrary number of focal lengths (μm), and λ ₀ represents an arbitrary number of light source wavelengths (μm).)   The optical member according to claim 4, wherein a height T of the rectangular structure body is 0.4 μm ≦ T ≦ 1.2 μm. The optical member according to any one of claims 4 to 7, wherein the rectangular structure is a group of structures satisfying the following conditions 1) to 5).
1) Width of group of m-th structure (μm): d _m = r _(m) −r _(m−1)
2) Width obtained by dividing the width of the m-th structure into an arbitrary number (μm):
g _m = d _m / x _m
(X _m represents an arbitrary integer of 1 or more in the m-th structure.)
3) i-th height (μm) at a position corresponding to the m-th structure:
_{T m (i) = {T} / (x m -1)} · (i-1)
(T represents the height of the rectangular structure, and i represents an integer of 1 to x _m .)
4) Duty ratio of the i-th structure existing in the group of the m-th structure:
t _{m (i)} = 1−T _{m (i)} / T
5) Width of the i-th structure existing in the group of the m-th structure: t _{m (i)} · g _m   The illuminating device comprised from the concave lens as described in any one of Claims 1-3, the optical member as described in any one of Claims 4-8, and a light source.   The lighting device according to claim 9, wherein the light source is a white LED. The illumination device according to claim 9, wherein the light source wavelength λ ₀ of the concave lens or the optical member is designed to be 0.555 ± 0.020 μm.   The illuminating device according to claim 9, wherein a focal length f of the concave lens or the optical member is 0.3 to 0.1 mm.

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