JP2015050028A - Lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a condition for making the in-plane luminance of light irradiated by an illumination device uniform. An illuminating device (1) is disposed opposite to a light source (2) having a predetermined divergence characteristic, a reflector (3) that specularly reflects light emitted from the light source (2), and opposed to the reflector (3). The direct light 21 directly incident on the light emitted from the light source 2 and the reflected light 22 incident on the light emitted from the light source 2 after being reflected by the reflecting plate 3 are incident on the opposite side of the reflecting plate 3. A light direction control plate 4 that emits light, and the light source 2 and the reflection plate 3 are installed such that the illuminance distribution on the light direction control plate 4 by the reflected light 22 has a peak at the center. . [Selection] Figure 1

Description

  The present invention relates to a planar illumination device.

  In recent years, lighting devices using LEDs have become widespread. However, since the LED is a point light source, it has not been used so much in lighting or the like that is attached to a ceiling surface or a wall surface where a lighting device having a large area such as a fluorescent lamp is required. In view of this, there has been disclosed an illuminating device having a structure in which elongated light emitting devices in which a plurality of LEDs are arranged in a row are arranged so as to face the inside of a thin casing and are radiated to the outside by a light direction control plate on the surface (Patent Document 1). And Patent Document 2).

  The techniques described in Patent Documents 1 and 2 attempt to make the luminance distribution uniform by forming parallel light by attaching a collimator lens to the LED and causing it to emit light, and reflecting the parallel light with a mountain-shaped scattering reflector. ing.

International Publication No. 2010-001604 JP 2008-060061 A

  In general, when there is unevenness in luminance of a lighting fixture, unevenness in illuminance occurs in the illuminated object, and therefore it is preferable that the in-plane luminance is uniform. For example, the techniques described in Patent Documents 1 and 2 make the in-plane luminance uniform when the parallel light emitted from the LED is diffused by a mountain-shaped scattering reflector and irradiated outside.

  However, the lighting devices disclosed in Patent Documents 1 and 2 have conditions such as a light emission angle determined by tests and the like, and it has been difficult to find the optimum conditions. In addition, it is possible to use an optical simulation such as a ray tracing method, but similarly, it is difficult to find an optimum condition. Therefore, it has been difficult to determine specific specifications of the lighting device. Furthermore, since parallel light is used for the light source and a diffuser plate is used for the reflector, it is difficult to make the in-plane luminance uniform.

  The present invention provides a condition for making the in-plane luminance of the light irradiated by the lighting device uniform. In particular, the in-plane luminance is made closer to uniform by utilizing the divergence characteristics of the light source and making the reflector a specular reflection.

An illumination device according to an embodiment of the present invention includes:
A light source disposed oppositely and having a predetermined divergence characteristic;
A reflector that specularly reflects the light emitted from the light source;
Directly incident light that is disposed facing the reflecting plate and directly incident on the light emitted from the light source and reflected light that is incident on the light reflected from the reflecting plate is incident on the reflecting plate. A light direction control plate that emits light on the opposite side of the plate;
With
The light source and the reflection plate are installed such that an illuminance distribution on the light direction control plate by the reflected light has a peak at the center.

Moreover, in the illuminating device of one Embodiment concerning this invention,
The reflection plate is formed in a convex shape toward the light direction control plate.

ただし、

であって、Ir(R)は、反射光による光方向制御板上の照度分布、
Ｌ０は、光方向制御板４の長さの半分、
Ｙは、光方向制御板４から光源２の中心までの距離、
θは、光源２の仰角、
σは、光源の配光分布の半値半幅の0.849倍、
αは、反射板３の傾斜角、
ｋは、比例定数、
である。 Moreover, in the illuminating device of one Embodiment concerning this invention,
The following formula is satisfied.

However,

Ir (R) is the illuminance distribution on the light direction control plate by the reflected light,
L0 is half the length of the light direction control plate 4,
Y is the distance from the light direction control plate 4 to the center of the light source 2,
θ is the elevation angle of the light source 2,
σ is 0.849 times the half width at half maximum of the light distribution of the light source,
α is the inclination angle of the reflector 3,
k is a proportionality constant,
It is.

ただし、Ｉｄは、前記直達光による前記光方向制御板上の照度分布のピーク値、
Ｉｒは、前記反射光による前記光方向制御板上の照度分布の中央における値、
である。 An illumination device according to an embodiment of the present invention includes:
A light source disposed oppositely and having a predetermined divergence characteristic;
A reflector that specularly reflects the light emitted from the light source;
Directly incident light that is disposed facing the reflecting plate and directly incident on the light emitted from the light source and reflected light that is incident on the light reflected from the reflecting plate is incident on the reflecting plate. A light direction control plate that emits light on the opposite side of the plate;
With
In the light source and the reflector, the peak value of the illuminance distribution on the light direction control plate by the direct light and the value at the center of the illuminance distribution on the light direction control plate by the reflected light satisfy the following expressions: Features.

However, Id is a peak value of illuminance distribution on the light direction control plate by the direct light,
Ir is a value at the center of the illuminance distribution on the light direction control plate by the reflected light,
It is.

ただし、

であって、Ir(R)は、反射光による光方向制御板上の照度分布、
Id(R)は、直達光による光方向制御板上の照度分布、
Ｌ０は、光方向制御板４の長さの半分、
Ｙは、光方向制御板４から光源２の中心までの距離、
θは、光源２の仰角、
σは、光源の配光分布の半値半幅の0.849倍、
αは、反射板３の傾斜角、
ｋは、比例定数、
である。 Moreover, in the illuminating device of one Embodiment concerning this invention,
The following formula is satisfied.

However,

Ir (R) is the illuminance distribution on the light direction control plate by the reflected light,
Id (R) is the illuminance distribution on the light direction control plate by direct light,
L0 is half the length of the light direction control plate 4,
Y is the distance from the light direction control plate 4 to the center of the light source 2,
θ is the elevation angle of the light source 2,
σ is 0.849 times the half width at half maximum of the light distribution of the light source,
α is the inclination angle of the reflector 3,
k is a proportionality constant,
It is.

  According to the present invention, the specific specification of the lighting device can be obtained, and the in-plane luminance of the light emitted by the lighting device can be made to be uniform.

It is a figure which shows the illuminating device of one Embodiment which concerns on this invention. The light direction control board of the illuminating device of one Embodiment which concerns on this invention is shown. The concept which makes the in-plane brightness | luminance of the illuminating device of one Embodiment which concerns on this invention approach uniformly is shown. The in-plane luminance of Reference Example 1 is shown. The in-plane luminance of Reference Example 2 is shown. It is a figure for demonstrating the conditions 1 of the reflected light of the illuminating device of one Embodiment which concerns on this invention. The mirror image of the light source 2 by the reflecting plate 3 of the illuminating device of one Embodiment which concerns on this invention is shown. The illuminance distribution of Comparative Example 1 is shown. The illuminance distribution of Example 1 of the illuminating device of one Embodiment which concerns on this invention is shown. The illuminance distribution of Comparative Example 2 is shown. The illumination intensity distribution of Example 2 of the illuminating device of one Embodiment which concerns on this invention is shown. An example in which the light source 2 is not in the middle of the reflecting plate 3 and the light direction control plate 4 in the y direction is shown.

  Hereinafter, a lighting device 1 according to the present invention will be described with reference to the drawings.

  FIG. 1 shows an illumination device 1 according to an embodiment of the present invention.

  The illumination device 1 of the present embodiment includes a light source 2, a reflection plate 3, and a light direction control plate 4. Here, one end of the light direction control plate 4 on the reflection plate 3 side is set as the origin, the direction toward the other end of the light direction control plate 4 on the reflection plate 3 side is the x direction, the direction toward the reflection plate 3 is the y direction, and x , The direction toward the back with respect to the paper surface forming the right-handed coordinate system with respect to the y direction is defined as the z direction.

  The light source 2 preferably uses two LED rows extending opposite to each other in the z direction. Each LED is provided with a lens 2a having photo-alignment characteristics. The optical orientation characteristic of the lens 2a is preferably widened in the z direction in order to reduce luminance unevenness in the z direction. Further, it is preferable that the photo-alignment characteristic of the lens 2a is moderately narrow in the y direction in order to ensure high luminance up to a position away from the light source 2.

  The reflection plate 3 is disposed to face the light direction control plate 4, and reflects toward the light direction control plate 4 when a part of the light emitted from the light source 2 is incident. The reflector 3 is preferably a metal reflective film such as aluminum or silver. The reflection plate 3 in the example shown in FIG. 1 has an inclined surface bent in a convex shape toward the light direction control plate 4 in the middle of the light source 2. The reflector 3 may be a flat surface.

  FIG. 2 shows the light direction control plate 4 of the illumination device 1 according to the embodiment of the present invention.

  The light direction control plate 4 is a member that emits an obliquely incident light beam in the front direction. For example, the light direction control plate 4 is preferably a prism sheet as shown in FIG. 2A or a diffusion sheet mixed with scattering particles 4a as shown in FIG. Further, as shown in FIG. 2C, both a prism sheet and a diffusion sheet mixed with the scattering particles 4a may be used.

  FIG. 3 shows a concept of making the in-plane luminance of the illumination device according to the embodiment of the present invention uniform. FIG. 4 shows the in-plane luminance of Reference Example 1. FIG. 5 shows the in-plane luminance of Reference Example 2.

  The illumination device 1 of the present embodiment has two lights that reach the light direction control plate 4 from the light source 2. As shown in FIG. 3, the two light beams are a direct light 21 that the light emitted from the light source 2 directly reaches the light direction control plate 4 and a light that is emitted from the light source 2 is reflected by the reflection plate 3 so that the light direction control plate. 4 is reflected light 22 that reaches 4. The direct light 21 and the reflected light 22 have peaks at different positions, respectively, and the peak of the reflected light 22 occurs at a position farther from the light source 2 than the peak of the direct light 21. The total distribution of the direct light 21 and the reflected light 22 is the sum of the direct light 21 and the reflected light 22. In this figure and subsequent figures, the thin solid line represents the illuminance distribution by the direct light 21, the dotted line represents the distribution by the reflected light 22, and the thick solid line represents the total distribution. Unless otherwise specified, each distribution represents the sum of two light sources.

  In the illumination device 1 of the present embodiment, it is preferable to satisfy two conditions in order to make the total distribution of the direct light 21 and the reflected light 22 uniform.

  The first condition is to form the total distribution of the direct light 21 and the reflected light 22 reaching the light direction control plate 4 from the light source 2 so as to be uniform near the center. When this condition is not satisfied, as shown in FIG. 4 shown as Reference Example 1, two peaks are generated at positions off the center. In this case, the peaks of the direct light 21 and the reflected light 22 overlap, the center becomes dark, and it is difficult to make the total distribution uniform.

  The second condition is to make the peak intensity of the direct light 21 reaching the light direction control plate 4 from the light source 2 and the peak intensity of the reflected light 22 substantially equal to the first condition. If this condition is not satisfied, the left and right peaks are different from the central peak as shown in FIG. 5 shown as the reference example 2, and it is difficult to make the total distribution uniform.

  In the coordinates shown in FIG. 1, Y is a constant indicating the position of the light source 2. Here, in FIG. 1, the illuminance at the coordinate X of the light direction control plate 4 by the light source 2 on the left side is divided into direct light 21 and reflected light 22.

  Strictly speaking, it is necessary to consider the distribution in the Z direction in FIG. 1, but considering that the light sources 2 are closely arranged and the light distribution in the Z direction is sufficiently wide, It can be considered uniform. In other words, in the present embodiment, only the illuminance distribution in the paper plane needs to be considered.

ただし、ｋは、比例係数、
G(X)は、光源２の配光特性、
D(X)は、光源２からの距離の二乗の逆数、
S(X)は、光方向制御板４に対する入射角の効果、
である。 First, the illuminance by the direct light 21 will be described. The illuminance by the direct light 21 is given by the following formula (1).

Where k is a proportional coefficient,
G (X) is the light distribution characteristic of the light source 2,
D (X) is the reciprocal of the square of the distance from the light source 2,
S (X) is the effect of the incident angle on the light direction control plate 4,
It is.

ただし、φは、光源２から測定点Ｘに向かう線分がＸ軸となす角、
θは、光源２の仰角、
σは、正規分布の標準偏差、
である。 G (X) is represented by the following formula (2). Here, the light distribution of the light source 2 is assumed to follow a normal distribution because it may be approximated to a normal distribution in general when the light distribution is narrowed using a lens.

However, φ is an angle formed by a line segment from the light source 2 to the measurement point X and the X axis,
θ is the elevation angle of the light source 2,
σ is the standard deviation of the normal distribution,
It is.

以下、標準偏差σを用いて説明するが、光源の配向分布が正規分布から外れる場合は、半値半幅σｈに置き換えて考えればよい。 Further, the standard deviation σ of the normal distribution and the half value half width σh have the relationship of the following formula (3).

In the following description, the standard deviation σ will be used. However, if the orientation distribution of the light source deviates from the normal distribution, it can be considered by replacing it with the half-value half-width σh.

Φ is expressed by the following equation (4).

Next, D (X) is expressed by the following equation (5). From the equations (1) and (5), it can be seen that the illuminance Id (X) by the direct light 21 is inversely proportional to the square of the distance from the light source 2.

Next, S (X) is represented by the following formula (6). It can be seen from the equations (1) and (6) that the illuminance Id (X) by the direct light 21 is proportional to the cosine of the incident angle.

Here, when the following parameter R≡X / Y is introduced for the sake of simplicity, the illuminance Id (X) by the direct light 21 is given by the following equation (7).

  Next, the illuminance by the reflected light 22 will be described.

  FIG. 6 is a diagram for explaining condition 1 of the reflected light 22 of the illumination device 1 according to the embodiment of the present invention. FIG. 7 shows a mirror image of the light source 2 by the reflector 3 of the illumination device 1 according to the embodiment of the present invention.

It can be seen from FIG. 7 that the illuminance Ir (X) by the reflected light 22 may be replaced by Y → 3Y and θ → 2α−θ, respectively, with respect to the equation (7). However, it is assumed that the distance from the light direction control plate 4 to the light source 2 and the distance from the light source 2 to the reflection plate 3 are equal and Y. By this replacement, the following equation (8) is obtained. Α is the inclination angle of the reflecting plate 3 and may be zero.

In the case of reflected light, when R≡X / 3Y and differentiated in order to investigate the shape of the Ir (R) graph shown in FIG. 6, the following equation (9) is obtained.

Expression (9) has the following characteristics as Expression (10) and Expression (11).

However, Rpr is R satisfying the following formula (11).

  This indicates that Ir (R) monotonously increases as R increases, and monotonically decreases after Rpr. It can be seen that Ir (R) has a single peak.

ただし、R0rは、光方向制御板４の中央におけるＲの値であって、以下の式（１４）で表す。

ただし、Ｌ０は、光方向制御板４の長さの半分、
Ｙは、光方向制御板４から光源２の中心までの距離、
である。 Therefore, Condition 1 is given by the following equation (13).

However, R0r is the value of R at the center of the light direction control plate 4, and is represented by the following formula (14).

However, L0 is half the length of the light direction control plate 4,
Y is the distance from the light direction control plate 4 to the center of the light source 2,
It is.

  The left side of Expression (13) represents the central illuminance, and the right side represents the illuminance at the peak position. Both sides of the equation (13) consider the contribution of the right light source 2 in addition to the left light source 2. This expression represents that the illuminance at the center of the left side is larger than the illuminance at the peak position on the right side.

Specific numerical examples of Comparative Example 1 that does not satisfy Condition 1 and Example 1 that satisfies Condition 1 are shown below. However, the value of Ir (R) was obtained by ignoring the first k / 9Y ^{2 on the} right side, which is a constant.

Comparative Example 1 Example 1
L0 300mm 300mm
Y 29mm 29mm
σ 5.1deg 5.1deg
(Equivalent to half-width half-width 6deg)
θ 0deg 0deg
α 0deg 3deg
result
R0 3.45 3.45
Rp 6.5 4.6
Ir (R0) 0.00014 0.0029
Ir (Rp) 0.00081 0.0045
Ir (2R0-Rp) 0.0000 0.0002
Left side of equation (13) 0.00028 0.0059
Right side of formula (13) 0.00081 0.0047
Condition 1 does not meet meets
(Left side <Right side) (Left side> Right side)

  FIG. 8 shows the illuminance distribution of Comparative Example 1. FIG. 9 shows an illuminance distribution of Example 1 of the lighting apparatus according to the embodiment of the present invention.

  Ir (R) represents the illuminance distribution due to the contribution of the left light source 2, and Ir (R) + Ir (2R0r-R) represents the illuminance distribution due to the contribution of the light sources 2 on both sides. In Comparative Example 1 that does not satisfy Condition 1, no peak occurs in the center, while in Example 1 that satisfies Condition 1, a peak occurs in the center. It can also be seen that it is possible to approximate the desired distribution by providing the reflecting plate 3 with an inclination α.

  Next, the second condition will be described.

ただし、Rpdは、直達光２１のピークを与えるＲであり、以下の式（１６）の解である。

また、R0dは、光方向制御板４の中央におけるＲの値であって、以下の式（１７）で表す。

The peak intensity of the direct light 21 is given by the following equation (15).

However, Rpd is R giving the peak of the direct light 21 and is a solution of the following formula (16).

R0d is a value of R at the center of the light direction control plate 4 and is expressed by the following equation (17).

When the peak of the direct light 21 and the median value of the reflected light 22 are equal, that is, when the ratio of the two satisfies the following formula (18), the illuminance is uniform.

However, since the luminance ratio of about 0.5 to 2 is an allowable range, the following expressions (19) and (20) are obtained as the condition 2.

In addition, it is more preferable when the following formula | equation (21) is satisfy | filled.

Specific numerical examples of Comparative Example 2 that does not satisfy Condition 2 and Example 2 that satisfies Condition 2 are shown below. However, the value of Ir (R) was obtained by ignoring the first k / Y ^{2 on the} right side, which is a constant.

Comparative Example 2 Example 2
L0 300mm 300mm
Y 29mm 29mm
σ 8.49deg 8.49deg
(Equivalent to half-width half-width of 10deg)
θ 0deg 0deg
α 0deg 5deg
result
R0r 3.45 3.45
Rpr 3.9 2.7
Ir (R0) 0.00353 0.0166
Ir (Rpr) 0.00365 0.0200
Ir (2R0r-Rpr) 0.00292 0.0115
Left side of formula (19) 0.00705 0.0332
Right side of formula (19) 0.00665 0.0315
Condition 1 Satisfy Meet

Rpd 3.9 3.9
Id (Rpd) 0.00365 0.00365
Id (2R0-2Rpd) 0.00019 0.00019
Molecule of formula (19) 0.00385 0.00385
Denominator of equation (19) 0.000783 0.00369
Ratio of formula (19) 4.91 1.04
Condition 2 does not meet meets
(2 <ratio of equation (19)) (0.5 <ratio of equation (19) <2)

  FIG. 10 shows the illuminance distribution of Comparative Example 2. FIG. 11 shows an illuminance distribution of Example 2 of the lighting apparatus according to the embodiment of the present invention.

  In Comparative Example 2, which does not satisfy the condition 2, the peak of the reflected light is in the center, but the peak of the direct light is stronger, so the total distribution is not uniform. In Example 2 that satisfies Condition 2, the peak of direct light and reflected light have the same value, so the total distribution approaches uniform.

  FIG. 12 shows an example in which the light source 2 is not in the middle between the reflector 3 and the light direction control plate 4 in the y direction.

For example, if the distance from the center of the light source 2 to the light direction control plate 4 is Yt, and the distance from the center of the light source 2 to the reflector 3 is Yb, Equation (7) is Equation (22) and Equation (8) is Expression (23) and Expression (14) are changed to Expression (24), and Expression (17) is changed to Expression (25).

  As described above, according to the present embodiment, specific specifications of the lighting device can be obtained, and the in-plane luminance of the light emitted by the lighting device can be made close to uniform.

  As mentioned above, although the illuminating device was demonstrated based on some Examples, this invention is not limited to these Examples, A various deformation | transformation is possible.

DESCRIPTION OF SYMBOLS 1 ... Illuminating device 2 ... Light source 21 ... Direct light 22 ... Reflected light 3 ... Reflecting plate 4 ... Light direction control board

Claims (5)

A light source disposed oppositely and having a predetermined divergence characteristic;
A reflector that specularly reflects the light emitted from the light source;
Directly incident light that is disposed facing the reflecting plate and directly incident on the light emitted from the light source and reflected light that is incident on the light reflected from the reflecting plate is incident on the reflecting plate. A light direction control plate that emits light on the opposite side of the plate;
With
The illumination device according to claim 1, wherein the light source and the reflection plate are installed such that an illuminance distribution on the light direction control plate by the reflected light has a peak at the center. The lighting device according to claim 1, wherein the reflection plate is formed in a convex shape toward the light direction control plate. The illuminating device of Claim 1 or Claim 2 which satisfy | fills the following formula | equation.

However,

Ir (R) is the illuminance distribution on the light direction control plate by the reflected light,
L0 is half the length of the light direction control plate 4,
Y is the distance from the light direction control plate 4 to the center of the light source 2,
θ is the elevation angle of the light source 2,
σ is 0.849 times the half width at half maximum of the light distribution of the light source,
α is the inclination angle of the reflector 3,
k is a proportionality constant,
It is. A light source disposed oppositely and having a predetermined divergence characteristic;
A reflector that specularly reflects the light emitted from the light source;
Directly incident light that is disposed facing the reflecting plate and directly incident on the light emitted from the light source and reflected light that is incident on the light reflected from the reflecting plate is incident on the reflecting plate. A light direction control plate that emits light on the opposite side of the plate;
With
In the light source and the reflector, the peak value of the illuminance distribution on the light direction control plate by the direct light and the value at the center of the illuminance distribution on the light direction control plate by the reflected light satisfy the following expressions: A lighting device.

However, Id is a peak value of illuminance distribution on the light direction control plate by the direct light,
Ir is a value at the center of the illuminance distribution on the light direction control plate by the reflected light,
It is. The illuminating device of Claim 4 which satisfy | fills the following formula | equation.

However,

Ir (R) is the illuminance distribution on the light direction control plate by the reflected light,
Id (R) is the illuminance distribution on the light direction control plate by direct light,
L0 is half the length of the light direction control plate 4,
Y is the distance from the light direction control plate 4 to the center of the light source 2,
θ is the elevation angle of the light source 2,
σ is 0.849 times the half width at half maximum of the light distribution of the light source,
α is the inclination angle of the reflector 3,
k is a proportionality constant,
It is.

Images