JP2009110828A - Led light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LED light source device capable of reducing luminance unevenness in arrangement direction of the LED. <P>SOLUTION: The LED light source device 1 in which a plurality of LEDs 6 are arranged in a row has a reflector 54 in which a reflecting surface 52 of paraboloid of revolution or ellipsoid of revolution is formed for every LED 6, and each of the reflecting surfaces 52 of the reflector 54 is formed so that a part in connection of the paraboloid of revolution or ellipsoid of revolution may be overlapped. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an LED light source device in which LEDs (Light Emitting Diodes) are arranged in a line.

Conventionally, as an inspection device for inspecting the presence or absence of defects such as scratches generated on a transparent body such as a glass substrate of a liquid crystal panel, a linear light source device is disposed opposite to a line sensor, and the space between them is an inspection target. An apparatus is known that transports a transparent body, receives linear light transmitted through the transparent body with a line sensor, and detects a defect based on the distribution of the amount of light received by the line sensor.
In recent years, a linear light source device in which light emitting elements are mounted in a row on a long substrate is known (see, for example, Patent Document 1).
JP 2007-194161 A

However, when the light source is configured by arranging the light emitting elements in a row, there is a problem that large luminance unevenness occurs in the luminance distribution along the arrangement direction of the light emitting elements.
This invention is made | formed in view of the situation mentioned above, and aims at providing the LED light source device which can reduce the brightness nonuniformity of the sequence direction of LED.

  In order to achieve the above object, according to the present invention, in an LED light source device in which a plurality of LEDs are arranged in a line, a reflecting body having a rotating surface of a rotating surface or a rotating ellipsoid is formed for each LED. And each of the reflecting surfaces of the reflector is formed so that a part of the rotating surface of the rotating object or the connecting surface of the ellipsoidal surface overlaps each other.

  Further, the present invention is characterized in that, in the above-mentioned invention, a diffusing material that diffuses light emitted from the reflecting surface and obtains a predetermined uniformity is obtained.

  According to the present invention, in the above invention, a circular diffusing material that diffuses light emitted from the reflecting surface in a circular direction and light diffused by being separated from the circular diffusing material are incident, and the LED is long in the arrangement direction of the LEDs. And an elliptical diffusing material that diffuses in an elliptical direction having an axis.

  Moreover, the present invention is characterized in that, in the above invention, a mirror is provided that reflects light of a component deviated from the elliptical diffuser out of the light diffused by the circular diffuser toward the elliptical diffuser.

  According to the present invention, each of the reflecting surfaces of the reflector is formed such that a part of the rotating surface or the ellipsoidal surface overlaps, so that the emitted light of the LED is collimated by the reflecting surface. In addition, surface light sources are formed on the respective reflecting surfaces, and the surface light sources are overlapped by the overlap, so that unevenness in luminance in the LED arrangement direction is reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration of an LED light source device 1 according to the present embodiment.
The LED light source device 1 includes an LED module 8 in which LEDs 6 are arranged in a row, and is configured as a linear light source device that emits linear line light by lighting each LED 6.
More specifically, the LED light source device 1 is configured by attaching an LED module 8 and an electrical box (not shown) to a long mounting frame 4, and further, the LED module 8 includes a heat radiation fin 32 </ b> A. A heat radiating plate 32 formed with is attached.

2A and 2B are diagrams showing the configuration of the LED module 8. FIG. 2A is a plan view, FIG. 2B is a cross-sectional view taken along the line II in FIG. 2A, and FIG. It is II-II arrow sectional drawing of 2 (A).
The LED module 8 is configured by arranging a plurality of LEDs 6 as light emitting elements in a row at regular intervals, and a plurality of LEDs 6, an LED mounting board 50 in which each LED 6 is mounted at regular intervals, and each LED 6 And a reflector 54 on which a reflecting surface 52 is formed.
The reflector 54 is formed of, for example, a rectangular parallelepiped, for example, an aluminum material, and a concave portion of a rotating ellipsoidal surface or a rotating solid surface is formed at intervals of the LEDs 6 along the longitudinal direction. Is. Each of the recesses constituting the reflecting surface 52 is truncated by the bottom surface of the reflector 54, and a substantially circular opening 56 is formed for each reflecting surface 52. By arranging such a reflector 54 so as to overlap the LED mounting substrate 50, the LED 6 is inserted into the reflecting surface 52 from the opening 56 of the reflector 54, and a spheroid or rotating object constituting the reflecting surface 52 is formed. The LEDs 6 are disposed on the rotation center axis of the surface, and the light emitted from each LED 6 is converted into substantially parallel light by the reflecting surface 52 and emitted.

More specifically, since the LED 6 basically has a point light source property, the LED 6 emits light with a light distribution characteristic of cos θ with respect to the optical axis. The area between the LEDs 6 is dark, and large luminance unevenness occurs in the direction along the array, which is inappropriate as a linear light source.
On the other hand, in the present embodiment, as described above, the LED 6 is disposed on the rotation center axis of the reflection surface 52 of the spheroid or rotating object surface, and as shown in FIG. Since the direct light k2 and the reflected light k1 reflected by the reflecting surface 52 are in the same direction, parallel light is extracted from the entire reflecting surface 52 as shown in FIG.
Thereby, since a surface light source is formed for each reflecting surface 52, the luminance unevenness in the direction along the array of the LEDs 6 is reduced as compared with the case where the LEDs 6 are simply arrayed.

Further, in the present embodiment, each of the reflecting surfaces 52 is not separated and arranged separately, but, for example, as shown in FIG. Each reflection surface 52 is formed so that a part of the surface overlaps (overlap), and as a result, between each of the reflection surfaces 52, as shown in FIG. A cutout 58 is formed.
Then, as shown in FIG. 2C, a part k3 of the light emitted from the LED 6 proceeds in the arrangement direction of the LEDs 6 through the cutout portion 58 of the reflecting surface 52, so that the luminance unevenness between the LEDs 6 is further reduced. It will be.
At this time, since each reflecting surface 52 is formed while overlapping the spheroid surface or rotating object surface, as shown in FIG. 4, the portion 52A having the minimum width in the arrangement direction of the LEDs 6 corresponds to the overlap. As a result, a line-shaped light having a certain width X is formed.

Here, it is as described above that the luminance unevenness between the LEDs 6 is reduced by arranging the reflecting surfaces 52 so as to overlap each other. However, as in the present embodiment, the opening 56 is formed at the bottom of the reflecting surface 52. When the LED 6 is inserted and arranged, for example, as shown in FIG. 4, a gap is generated between the LED 6 and the reflecting surface 52, and uneven brightness occurs. Further, unevenness in luminance also occurs due to non-light emitting portions such as electrodes of the LED 6.
Therefore, in this embodiment, in order to further reduce the luminance unevenness along the arrangement direction of the LEDs 6, a diffusion plate having a lens function (hereinafter referred to as “diffuse lens”) is provided.

FIG. 5 is a cross-sectional view of the LED light source device 1.
In the LED light source device 1, the LED module 8 is disposed by a substantially L-shaped LED support frame 36 between the base frame 30 to which the heat radiating plate 32 is attached and the attachment frame 4. A circuit board 34 on which a driver circuit 86 (see FIG. 8) for driving LEDs is mounted is disposed below the circuit board 34.
As shown in the figure, the LED light source device 1 includes a circular diffusion lens 60 and an elliptical diffusion lens 62 that are spaced apart from each other along the light emission direction of the LED module 8.
More specifically, the circular diffusion lens 60 is a diffusion plate that is placed on the upper surface of the LED module 8 and diffuses the light emitted by the LED module 8 into a circle. As a result, the light emitted from each LED 6 of the LED module 8 is collimated by the reflecting surface 52, further diffused while being spread in the circular direction by the circular diffusion lens 60, and then enters the elliptical diffusion lens 62.
The elliptical diffusion lens 62 is a diffusion plate that is provided from one end to the other end of the mounting frame 4 and diffuses the diffused light diffused by the circular diffusion lens 60 into an ellipse. The major axis direction of the elliptical diffusion is the longitudinal direction of the LED module 8. The direction is the same. Thereby, the light emitted from each LED 6 of the LED module 8 is diffused while being spread in the longitudinal direction of the LED module 8, and uneven brightness between the LEDs 6 is suppressed.

FIG. 6 shows measured values of relative luminance in the LED arrangement direction when five LEDs 6 are arranged in a row at a pitch of 20 mm. FIG. 6A shows a case where LEDs 6 are simply arranged, FIG. 6B shows the case where the reflector 54 is provided on the LED 6, FIG. 6C shows the case where the reflector 54 and the circular diffusion lens 60 are provided on the LED 6, and FIG. A case where a diffusion lens 60 and an elliptical diffusion lens 62 are provided is shown.
As shown in these drawings, it is shown that the luminance is secured between the LEDs 6 by providing the reflectors 54 on the LEDs 6, and further, the circular diffusion lens 60 and the elliptical diffusion that are spaced apart from each other are shown. By using the lens 62 in combination, a substantially uniform luminance distribution can be obtained in the arrangement direction of the LEDs 6 as shown in FIG.
Note that the number of the diffusion lenses is the number (1 to a plurality) of the luminance or illuminance uniformity required for the LED light source device 1 [= (maximum value−minimum value) / maximum value]. It ’s fine.

  Here, since the circular diffusion lens 60 and the elliptical diffusion lens 62 are spaced apart from each other as shown in FIG. 5, the base frame 30 and the LEDs are deviated from the elliptical diffusion lens 62 by the diffused light from the circular diffusion lens 60. A component that is incident on each surface of the support frame 36 and becomes a loss occurs. Therefore, a mirror 64 is affixed between the circular diffusion lens 60 and the elliptical diffusion lens 62 on the opposing surfaces of the base frame 30 and the LED support frame 36, and the light incident on these opposing surfaces is applied to the mirror 64. Then, the light is reflected and incident on the elliptical diffusion lens 62 to suppress the loss of the light amount.

Next, the light amount control of the LED light source device 1 will be described.
In general, when the LED 6 is driven to be lit, a forward current If (= (E−Vf) / R) when the current limiting resistor R and the LED 6 are connected in series with the constant voltage E and Vf is a forward voltage. ) Or the LED 6 is always driven to be lit with a constant current, and in any case, the lit drive is performed by controlling the forward current proportional to the luminous flux.

However, the proportional relationship between the luminous flux and the forward current is established when the temperature is substantially constant, and the proportional relationship between the luminous flux and the forward current is destroyed by the heat generation of the LED 6 or the ambient temperature, and the forward current is constant. As the temperature increases, the luminous flux decreases.
For example, when the temperature of the coupling point (hereinafter referred to as “junction”) between the LED 6 and the LED mounting substrate 50 is 25 ° C., the luminous flux when the LED 6 is driven at 3 W (watts) is set to 100%. If the LED 6 is continuously driven in the state, when the thermal resistance from the air to the junction is 15 ° C / W and the ambient temperature is 25 ° C, the temperature of the junction reaches about 75 ° C and the luminous flux is reduced by about 15%. To do.
That is, in the conventional lighting drive control, there is a problem that when the LED 6 is repeatedly turned on and off, a stable luminous flux cannot be obtained.
Therefore, in the present embodiment, the light quantity of each LED 6 is monitored, and feedback control is performed to increase or decrease the drive current (the forward current) so as to cancel the fluctuation of the light quantity, thereby stabilizing the light flux.

More specifically, the LED module 8 is provided with a light receiving element 70 for detecting the light quantity of a predetermined number of LEDs 6 as shown in FIG. The light receiving element 70 is attached to the base frame 30.
Specifically, as shown in FIG. 7A, the light receiving element 70 is arranged in the arrangement direction of the LEDs 6 for each predetermined number (five in the illustrated example) of LEDs 6 along the longitudinal direction of the LED module 8. The LED 6 (circular diffusion lens 60) is disposed at a predetermined height H from the center, and as shown in FIG. 7B, the emitted light from the LED 6 is shielded in the cross-sectional direction. In order to prevent this, the LED 6 is disposed at a position deviating from the optical axis f of the LED 6 and where the leaked light k4 of the LED 6 is incident.
The height H is a height at which diffused light radiated from the LEDs 6 at both ends of the predetermined number of LEDs 6 and diffused by the circular diffusion lens 60 can reach. The light receiving element 70 is arranged at such height H. By providing, a change in the amount of light of each predetermined number of LEDs 6 can be influenced by the amount of light received by one light receiving element 70.

FIG. 8 is a block diagram showing a functional configuration of the LED unit 2 for feedback control.
The LED light source device 1 includes an LED 80, a reflector 54 having a reflecting surface 52, a circular diffusion lens 60, and a light receiving element 70, an amplifier 80 that outputs a voltage signal corresponding to the amount of light detected by the light receiving element 70, and A reference voltage circuit 82 that outputs, as a reference voltage, a voltage signal when a desired luminous flux is obtained by light emission of the LED 6, a comparator 84 that outputs a difference signal corresponding to the difference between the voltage signal from the amplifier 80 and the reference voltage, A driver circuit 86 that corrects the drive current so as to obtain a desired light flux based on the difference signal and outputs the corrected light to the LED 6 is provided. With these configurations, the drive current of the LED 6 is feedback-controlled.

That is, when the light amount of the LED 6 decreases due to heat generation or an increase in ambient temperature, the voltage signal falls below the reference voltage, so that the driver circuit 86 adds a correction for increasing the current value to the drive current, and the LED 6 emits light. It will be strengthened.
Therefore, even if the proportional relationship between the luminous flux and the driving current is lost due to the heat generation of the LED 6 or the ambient temperature, and the desired luminous flux cannot be obtained, the driving current is feedback-controlled so that the desired luminous flux is obtained. Therefore, a stable light beam can be obtained.

  At this time, there is a risk that the LED 6 will be destroyed if the driving power is increased indefinitely in accordance with the decrease in the luminous flux. Therefore, the LED light source device 1 is provided with an overcurrent protection circuit 88, and the overcurrent protection circuit 88 suppresses the drive current to a predetermined threshold value or less, whereby an overcurrent is applied to the LED 6. It is prevented from being destroyed. The predetermined threshold is a value determined in consideration of a predetermined margin with respect to an overcurrent value that causes destruction of the LED 6.

FIG. 9 is a diagram showing the characteristics obtained by the feedback control, FIG. 9A shows the rise characteristics, and FIGS. 9B and 9C show the temperature characteristics. In these figures, the measured value is expressed by a relative value with the measured value when the ambient temperature is 25 ° C. being 100%.
As shown in FIG. 9A, the above feedback control makes it possible to suppress the time from the start of lighting of each LED 6 until the luminous flux (light quantity) is stabilized within about 1 msec, and the rise is very high. It is shown that it is getting faster.
Further, since the LED 6 has a characteristic that the luminous flux decreases as the temperature rises, as shown in FIG. 9B, when the ambient temperature changes between 0 ° C. and 40 ° C., the ambient temperature increases at a high temperature. Together, the forward current is shown to increase. As a result, as shown in FIG. 9C, even when the ambient temperature changes between 0 ° C. and 40 ° C., the relative luminance fluctuation is suppressed within a range of about 5%, and about 0.125%. A stability of / ° C will be obtained.

  As described above, according to the present embodiment, each of the reflection surfaces 52 of the reflector 54 is formed by overlapping a part of the rotating surface of the rotating object or the ellipsoid of rotation. The radiated light of the LEDs 6 is collimated to form a surface light source on each reflecting surface, and furthermore, the surface light sources are overlapped by the overlap, thereby reducing uneven brightness in the arrangement direction of the LEDs 6.

  Further, according to the present embodiment, since the circular diffusion lens 60 and the elliptical diffusion lens 62 are used as the diffusion that diffuses the light emitted from the reflection surface 52 and obtains a predetermined degree of uniformity, the luminance unevenness in the arrangement direction of the LEDs 6 is determined. And a predetermined uniformity can be obtained.

  Further, according to the present embodiment, since the mirror 64 that reflects the component of the diffused light diffused by the circular diffuser lens 60 so as to be incident on the elliptical diffuser lens 62 is provided, the loss of light amount is reduced. Can be suppressed.

In addition, embodiment mentioned above shows the one aspect | mode of this invention to the last, A deformation | transformation and application are arbitrarily possible within the scope of the present invention.
For example, in the above-described embodiment, the LED modules 8 are configured by arranging the LEDs 6 in a straight line. However, the present invention is not limited to this, and the LEDs 6 may be arranged along a curve as long as the LEDs 6 are arranged in a linear form. May be.

The figure which shows the structure of a LED light source device. It is a figure which shows the structure of an LED module, (A) is a top view, (B) is the II-II arrow sectional drawing of (A), (C) is the II-II arrow sectional drawing of (A). . The figure for demonstrating the parallel light of an LED module. The figure which shows the overlap of the reflective surface of an LED module. It is the figure which looked at the cross section of the LED light source device. The figure which shows the measured value of the relative brightness | luminance in the LED arrangement direction at the time of arranging 5 LED in a line at 20 mm pitch. The figure for demonstrating the arrangement | positioning location of a light receiving element. The block diagram which shows the functional structure of a LED light source device. It is a figure which shows the characteristic of the LED light source device obtained by feedback control, (A) shows a rise characteristic, (B) and (C) show a temperature characteristic.

Explanation of symbols

1 LED light source device 4 Mounting frame 6 LED
8 LED Module 36 LED Support Frame 52 Reflecting Surface 54 Reflector 58 Notch 60 Circular Diffusing Lens 62 Elliptical Diffusing Lens 64 Mirror 70 Light Receiving Element 80 Amplifier 82 Reference Voltage Circuit 84 Comparator 86 Driver Circuit 88 Overcurrent Protection Circuit

Claims (4)

In the LED light source device formed by arranging a plurality of LEDs in a row,
A reflector having a rotating surface or a rotating ellipsoidal reflecting surface is formed for each LED.
Each of the reflective surfaces of the reflector is formed so that the rotating surface of the rotating object or a part of the rotating ellipsoid connected to each other overlaps. The LED light source device according to claim 1,
An LED light source device comprising a diffusing material that diffuses light emitted from the reflecting surface to obtain a predetermined degree of uniformity. The LED light source device according to claim 2,
A circular diffusing material that diffuses light emitted from the reflecting surface in a circular direction;
An LED light source device comprising: an elliptical diffusing material that receives light diffused by being separated from the circular diffusing material and diffuses in an elliptical direction having a major axis in the arrangement direction of the LEDs. The LED light source device according to claim 3.
The LED light source device characterized by providing the mirror of the light diffused by the circular diffusing material to reflect the light deviating from the elliptic diffusing material toward the elliptic diffusing material.

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