JP7025683B2 - Light source device - Google Patents

Description

The present invention relates to a light source device, and more particularly to a light source device including a plurality of LED elements.

Conventionally, light processing technology utilizing light has been used in various fields, and for example, an exposure apparatus has been used for microfabrication using light. In recent years, exposure technology has been developed in various fields, and is used for producing relatively large patterns and three-dimensional microfabrication among microfabrication. More specifically, exposure technology is used, for example, in the production of LED electrode patterns and the manufacturing process of MEMS (Micro Electro Mechanical Systems) represented by an accelerometer.

In these light processing techniques, a discharge lamp having high brightness has long been used as a light source. However, with the recent progress in solid-state light source technology, it is being considered to use a light source in which a plurality of LED elements are arranged.

The following Patent Document 1 discloses an optical system in which light emitted from a plurality of LED elements is converted into parallel light, then condensed, and incident on a rod integrator. In Patent Document 2 below, light emitted from a plurality of LED elements is passed through a lens array to generate a magnified real image as a secondary light source, and then the light emitted from the magnified real image is transmitted through a condenser lens. The optical system leading to the irradiated surface is disclosed.

Japanese Unexamined Patent Publication No. 2014-207300 Japanese Unexamined Patent Publication No. 2006-133635

The LED element is an element that emits light by passing a current through the semiconductor layer, and the light emitting surface of the LED element tends to have a region with high luminance and a region with low luminance, and uneven luminance occurs depending on the location. Cheap. For example, in the case of a configuration in which an electrode for supplying a current to the semiconductor layer is arranged on the light emitting surface side of the LED element, the electrode forming portion is a non-light emitting region, so that the portion where the electrode is formed and the electrode are Luminance distribution inevitably occurs in places where it is not formed. Further, even in the case of the configuration in which the electrode for supplying the current to the semiconductor layer is arranged on the surface opposite to the light emitting surface of the LED element, the region in the vicinity where the electrode is arranged and the above-mentioned region. There may be a difference in current density between the region and the region away from the region, and the brightness distribution may occur based on this difference. Further, in the case of a configuration in which an electrode for supplying a current to the semiconductor layer is arranged on the surface opposite to the light emitting surface of the LED element, the electrode on the back surface side is reflected on the light emitting surface side as it is. It is also conceivable to form a region with low brightness on the light emitting surface.

In the technique of Patent Document 1, after collimating the emitted light from each LED element, the light is condensed by the condenser lens, and the rod integrator is arranged at the focal position of the condenser lens. Therefore, high brightness is realized because the emitted light from each LED element is collected at almost one point on the light incident surface of the rod integrator.

However, the light emitting surface itself of each LED element appears as an image on the light incident surface of the rod integrator. Therefore, the above-mentioned luminance unevenness exists on the incident surface. In the rod integrator, the incident light is mixed by repeating reflection, so that it is expected that the illuminance unevenness is suppressed on the light emitting surface of the rod integrator as compared with the light incident surface. However, in order to fully realize this effect, it is necessary to arrange a relatively large rod integrator where it is necessary to secure a sufficient number of reflections.

In the technique of Patent Document 2, a secondary light source is substantially generated by arranging an enlarged real image of each LED element by a lens array provided in front of a condenser lens. Since this secondary light source is arranged in a state where it is narrower than the distance between the adjacent LED elements, the uneven brightness due to the existence of the non-light emitting region due to the distance between the adjacent LED elements is alleviated. Has been done. Then, the light emitted from the condenser lens is formed so as to be focused at different positions according to the divergence angle, so that a smooth illuminance distribution is realized on the irradiation surface. As a result, the illuminance unevenness caused by the luminance unevenness existing on the light emitting surface of each LED element is alleviated.

However, since the optical system collects light at different positions on the irradiation surface, the average brightness in the effective irradiation region is inevitably lower than the maximum brightness in the irradiation region. In the method of Patent Document 2, it is considered that measures against this decrease in brightness are taken by arranging a plurality of stages of lens arrays, but the optical system becomes complicated, the scale of the apparatus is expanded, and complicated optical axis adjustment is required. There is the issue of inviting.

In view of the above problems, it is an object of the present invention to realize a light source device that suppresses a decrease in luminance and suppresses uneven illuminance by a simple optical system configuration.

The light source device according to the present invention is
A light source unit that includes multiple LED elements,
The first optical system that narrows the divergence angle of the light emitted from the light source unit without collimating it.
A second optical system that collects the light emitted from the first optical system and
The incident surface is provided with an integrator optical system arranged at the focal position of the second optical system.

According to the above configuration, the plurality of light rays emitted from the plurality of LED elements and incident on the second optical system are non-parallel. Therefore, at the focal position of the second optical system, these plurality of light rays are not focused at one point, but are focused in a region having a predetermined size. Since the incident surface of the integrator optical system is arranged at this focal position, the image of the LED element itself does not appear clearly on the incident surface of the integrator optical system, but the image appears in a so-called "out of focus" state. ..

The above configuration guides light to the incident surface of the integrator optical system in such a deliberately out-of-focus state. At this time, the luminance unevenness caused by the presence of the light emitting region and the non-light emitting region composed of the electrodes and the like on the light emitting surface of the LED element also appears on the incident surface of the integrator optical system in a blurred state. As a result, a part of the low-luminance region corresponding to the place where the light beam emitted from the place where the electrode was present (non-light emitting region) on the LED element is guided, and the light ray emitted from the light emitting region are guided. A portion of the bright area corresponding to the location overlaps on the incident surface of the integrator optical system. As a result, as compared with the configuration of Patent Document 1, the luminance unevenness on the incident surface of the integrator optical system is reduced, and the illuminance unevenness on the irradiation surface of the light emitted from the integrator optical system is reduced. The term "irradiated surface" as used herein means a region where the light emitted from the light source device of the present invention is planned to be used.

Further, according to the above configuration, the light emitted from a plurality of LED elements can be realized by simply guiding the light emitted from the plurality of LED elements to the incident surface of the integrator optical system in a defocused state, which is extremely simple as compared with the configuration of Patent Document 2. It can be realized with a simple optical system. Further, since the incident surface of the integrator optical system is the focal position of the second optical system, high brightness is guaranteed for the light incident on the incident surface of the integrator optical system. Then, this high-luminance light is emitted onto the irradiation surface via the integrator optical system. That is, it is possible to guide high-intensity light to the irradiation surface as compared with the configuration of Patent Document 2.

Further, according to the above configuration, for example, by adjusting the distance between the first optical system and the second optical system, the focus of the image guided to the incident surface of the integrator optical system can be easily adjusted. If the image is adjusted in the focusing direction, the brightness on the incident surface of the integrator optical system can be increased, but the uneven brightness on the incident surface tends to appear. On the contrary, if the image is adjusted in the direction of being out of focus, the uneven brightness on the incident surface of the integrator optical system can be further eliminated, while the brightness on the incident surface is lowered. It is possible to respond flexibly according to the request of the application that uses the light emitted from the light source device.

The LED element has a light emitting surface and a linear electrode provided so as to separate the light emitting surface on the side facing the first optical system.
The maximum emission angle of the light ray emitted from the center point of the LED element is θ ₁ , the focusing angle after the light ray is emitted from the second optical system is θ ₂ , the width of the electrode is d ₁ , and the light ray is The first is such that the value of L ₁ satisfies the following equation (1), where L ₁ is the length orthogonal to the optical axis when crossing the focal position after the second optical system is ejected. It may be assumed that the positions of one optical system and the second optical system are adjusted.
2d ₁・ (θ ₁ / θ ₂ ) ≦ L ₁ ≦ 50d ₁・ (θ ₁ / θ ₂ ) ‥‥‥ (1)

The integrator optical system may be composed of a fly-eye lens in which a plurality of lenses are arranged in a matrix.

According to the light source device of the present invention, it is possible to suppress both the decrease in luminance and the unevenness of illuminance by using a simple optical system.

It is a drawing which shows an example of the optical system of a light source apparatus schematically. It is a schematic plan view of the LED element. It is a drawing which shows typically the image on the light incident surface of a fly eye lens when the LED element is in focus with respect to a fly eye lens. FIG. 3 is a drawing showing only each region of the fly-eye lens extracted from FIG. 3A. It is a drawing which shows typically the image on the irradiation surface when the LED element is in focus with respect to a fly eye lens. It is a drawing which shows typically the image on the irradiation surface when the LED element is out of focus with respect to a fly eye lens. It is a drawing which shows typically the light ray emitted from one LED element. It is a figure which shows typically the optical system of the light source apparatus of another embodiment. It is a figure which shows typically the optical system of the light source apparatus of another embodiment.

Hereinafter, the light source device of the present invention will be described with reference to the drawings. The dimensional ratio in each figure does not always match the actual dimensional ratio.

FIG. 1 is a drawing schematically showing an example of an optical system of a light source device. The light source device 1 includes a light source unit 2, a first optical system 5, a second optical system 7, and an integrator optical system 8.

The light source unit 2 includes a plurality of LED elements 3. In the present embodiment, as an example, the plurality of LED elements 3 are arranged on a predetermined plane (here, the XY plane). However, in the present invention, any arrangement of the plurality of LED elements 3 may be used. In FIG. 1, the direction of the optical axis 11 is the Z direction.

The first optical system 5 is an optical system that narrows the divergence angle without collimating the light emitted from the plurality of LED elements 3, and is configured by arranging a plurality of lenses 6 corresponding to each LED element 3. There is. In FIG. 1, a configuration in which one lens 6 is arranged corresponding to each LED element 3 is shown, but a plurality of lenses 6 are arranged in the direction of the optical axis 11 corresponding to each LED element 3. It doesn't matter.

The second optical system 7 is an optical system that focuses the light emitted from the first optical system 5 on the focal point 7f of the second optical system 7.

In the present embodiment, the integrator optical system 8 is configured by the fly-eye lens 10. The fly-eye lens 10 is arranged so that its incident surface 10a is at the position of the focal point 7f of the second optical system 7. However, in the present specification, "placed in the focal position" means that the focal length is completely aligned with the focal length, and that the focal length is moved in a direction parallel to the optical axis 11 by ± 10%. It shall be a concept including position. The optical axis 11 in FIG. 1 is an axis orthogonal to the incident surface of the integrator optical system 8, that is, the incident surface 10a of the fly-eye lens 10.

The light emitted from each LED element 3 passes through the first optical system 5 and the second optical system 7 and travels toward the incident surface 10a of the fly-eye lens 10. Since the second optical system 7 is a condensing optical system, each light ray travels toward the focal point 7f of the second optical system 7. However, as described above, the light rays emitted from the first optical system 5 are not collimated. Therefore, the light incident on the incident surface 10a of the fly-eye lens 10 is not focused at one point but is collected in the region 13 having a width.

At this time, the image of the LED element 3 appears in a blurred state on the incident surface 10a of the fly-eye lens 10. That is, the image is displayed in a state where it is out of focus. In FIG. 1, the position where the image of the LED element 3 is formed when the fly-eye lens 10 is not present is indicated by the reference numeral 15.

FIG. 2 is a schematic plan view of the LED element 3 when viewed from the light extraction surface side, that is, the first optical system 5 side in the Z-axis direction. The LED element 3 has a light emitting region 22 from which light generated in the semiconductor layer is taken out, and a linear electrode 21 for supplying a current to the semiconductor layer. In FIG. 2, a wire 14 for supplying a current from the outside to the electrode 21 is connected.

The electrode 21 is composed of, for example, Ni / Al / Ni / Ti / Au, Cr / Au, Ti / Pt / Au, Ti / Pt / Cr / Au / Cr / Pt / Au, and the like. That is, the electrode 21 is made of a material that hardly or hardly transmits the light generated by the LED element 3, and constitutes a non-light emitting region. That is, the light emitting surface of the LED element 3 has a light emitting region 22 and a non-light emitting region including the electrode 21.

As described above, according to the configuration of the present embodiment, an image of the LED element 3 in a defocused state appears on the incident surface 10a of the fly-eye lens 10. As a result, a part of the image of the non-light emitting region consisting of the electrodes 21 overlaps with a part of the image of the light emitting region 22. As a result, light with reduced luminance unevenness is incident on the incident surface 10a.

Further, the incident surface 10a of the fly-eye lens 10 is arranged at the focal position of the second optical system 7. Therefore, the light emitted from all the LED elements 3 is condensed in the narrow region 13 on the incident surface 10a, and the light having high brightness is incident on the fly-eye lens 10. This makes it possible to provide high-luminance light for an application that utilizes the light emitted from the fly-eye lens 10.

3A-3D are drawings schematically showing the operation of the present invention. 3A to 3C are drawings schematically showing an image on the light incident surface of the fly-eye lens 10 when the LED element 3 is in focus with respect to the fly-eye lens 10. The case where the LED element 3 is in focus with respect to the fly-eye lens 10 is, for example, in FIG. 1, when the light emitted from the LED element 3 is collimated and then incident on the second optical system 7. Corresponds.

FIG. 3A is a drawing schematically showing an image on an incident surface of the fly-eye lens 10, and FIG. 3B is a drawing in which only each region of the fly-eye lens 10 is extracted from FIG. 3A. 3A and 3B schematically show how the image 21b of the electrode 21 and the image 22b of the light emitting region 22 appear on the incident surface of each fly-eye lens 10.

As shown in FIGS. 3A and 3B, when the LED element 3 is in focus with respect to the fly-eye lens 10, the light emitted from the fly-eye lens 10 is on the irradiation surface as shown in FIG. 3C. , The image 3b of each LED element 3 is superimposed and displayed. As a result, on the irradiation surface, a difference in brightness is likely to appear between the region where the images 21b of the electrodes 21 overlap and the region where the images 22b of the light emitting region 22 overlap. In FIG. 3C, the image of the outer peripheral portion of the fly-eye lens 10 is represented by 10b.

On the other hand, when the LED element 3 is out of focus with respect to the fly-eye lens 10 as in the present embodiment, the image 10b on the outer peripheral portion of the fly-eye lens 10 is out of focus as shown in FIG. 3D. The image 21b of the electrode 21 and the image 22b of the light emitting region 22 are offset and superposed. As a result, the difference in brightness on the irradiation surface is alleviated as compared with the state of FIG. 3C.

FIG. 4 is a drawing schematically showing a light beam emitted from one LED element 3. In FIG. 4, θ ₁ is the maximum emission angle of the light ray emitted from the center point of the LED element 3, and θ ₂ is the light ray emitted from the center point of the LED element 3 emitted from the second optical system 7. It is the later focusing angle. Further, L ₁ is a length orthogonal to the optical axis 11 when the light beam crosses the focal position 7f of the second optical system 7 after being emitted from the second optical system 7.

In FIG. 2, assuming that the width of the electrode 21 included in the LED element 3 is d ₁ , the positions of the first optical system 5 and the second optical system 7 are preferably adjusted so as to satisfy the following equation (1). ..
2d ₁・ (θ ₁ / θ ₂ ) ≦ L ₁ ≦ 50d ₁・ (θ ₁ / θ ₂ ) ‥‥‥ (1)

If the size of L ₁ is made too small, the brightness of the fly-eye lens 10 on the incident surface 10a increases, but the light emitting region 22 on the LED element 3 and the electrodes 21 constituting the non-light emitting region clearly appear. It ends up. As a result, the brightness variation on the incident surface 10a becomes apparent. On the other hand, if the size of L ₁ is made too large, the boundary between the light emitting region 22 on the LED element 3 and the electrode 21 is blurred, and the brightness variation on the incident surface 10a of the fly-eye lens 10 is eliminated, but the incident surface is eliminated. The brightness on 10a is reduced.

The size of the non-light emitting region depends on the width of the electrode 21. Therefore, in the LED element 3 having a large width of the electrode 21, the brightness variation on the incident surface 10a is likely to appear. In such a case, by increasing the degree of out-of-focus on the incident surface 10a, the performance of reducing the luminance variation is enhanced. On the contrary, in the LED element 3 in which the width of the electrode 21 is small, the degree of defocus is reduced and the brightness on the incident surface 10a is increased. As a result, it is possible to provide an application that uses light with light in which both a decrease in luminance and uneven illuminance are suppressed.

As an example, if θ ₁ = 120 °, θ ₂ = 3 °, and d ₁ = 15 μm, 1.2 mm ≤ L ₁ ≤ 30 mm. As possible values, θ ₁ is 60 ° or more and 150 ° or less, θ ₂ is 1 ° or more and 50 ° or less, and d ₁ is 5 μm or more and 100 μm or less.

[Another Embodiment]
Hereinafter, another embodiment will be described.

<1> In the above-described embodiment, it is assumed that each optical system is arranged so that the position 15 where the image of the LED element 3 is formed is located at a position after the incident surface 10a of the fly-eye lens 10. did. However, as shown in FIG. 5, even if each optical system is arranged so that the position 15 where the image of the LED element 3 is formed is a position before the incident surface 10a of the fly-eye lens 10. I do not care. Even in this case, the image of each LED element 3 appears in the region 13 on the incident surface 10a of the fly-eye lens 10 in a defocused state.

<2> In the above-described embodiment, the case where the integrator optical system 8 is composed of the fly-eye lens 10 has been described. However, as shown in FIG. 6, it is also possible that the integrator optical system 8 is composed of the rod integrator 30.

The rod integrator 30 is a light guide member having a function of equalizing the illuminance distribution of light on the injection surface 30b by guiding the light incident on the incident surface 30a to the injection surface 30b while repeating total reflection on the side surface. This is an example of (optical guide). Such a light guide member is composed of, for example, a columnar member made of a light-transmitting material such as glass or resin, a hollow member whose inner surface is made of a reflecting mirror, or the like. The latter configuration is sometimes referred to as a light tunnel in particular. In the light guide member, a plurality of optical paths may be divided in a direction parallel to the optical axis.

However, the fly-eye lens 10 is an optical member that aims to make the illuminance uniform by superimposing the images of the divided lenses on the irradiation surface, whereas the rod integrator 30 emits light from the light emitting surface. It is an optical member that makes the illuminance uniform by repeatedly reflecting light inside the rod integrator 30. Therefore, the fly-eye lens 10 is more susceptible to the difference in brightness on the light emitting surface of the LED element 3 than the rod integrator 30. Therefore, as described in the above embodiment, when the integrator optical system 8 is composed of the fly-eye lens 10, the effect of eliminating the luminance unevenness can be further ensured.

<3> The present invention does not exclude an aspect in which a reflected optical system is appropriately arranged between the light source unit 2 and the first optical system 5 to change the traveling direction of light. Further, the present invention excludes an embodiment in which each LED element 3 included in the light source unit 2 is generally arranged on an XY plane, and some LED elements 3 are arranged so as to be displaced in the Z direction. is not it. The same applies to the case where the reflective optical system is appropriately arranged between the light source unit 2 and the first optical system 5, and the plane on which each LED element 3 is generally arranged is a plane different from the XY plane.

<4> In the above-described embodiment, the LED element 3 has been described as having the electrode 21 formed on the surface on the same side as the light emitting region 22, but the electrode is formed on the surface on the side opposite to the light emitting region 22. It doesn't matter if it is. Even in this case, the luminance distribution can occur in the plane of the light emitting region 22 depending on the position of the electrode and the distance from the electrode. Such a luminance distribution occurs similarly for each LED element 3 as long as the LED elements 3 are manufactured with the same design. Therefore, when the light emitted from each LED element 3 is collimated and then condensed, the same problem occurs.

Therefore, even when the light source unit 2 has a plurality of LED elements 3 having electrodes formed on the surface opposite to the light emitting region 22, the light emitted from the light source unit 2 can be collected by the first optical system 5. After narrowing the divergence angle without collimating with the light source, the light is focused by the second optical system and incident on the integrator optical system 8 arranged at the position of the focal point 7f of the second optical system 7 to cause the integrator optical system 8 to be incidental. Since the image of the LED element 3 appears on the incident surface in a “blurred” state, the effect of alleviating the unevenness of brightness on the incident surface of the integrator optical system 8 can be obtained.

1: Light source device 2: Light source unit 3: LED element 3a, 3b: Image of LED element 5: First optical system 6: Lens 7: Second optical system 7f: Focus of second optical system 8: Integrator optical system 10: Fly-eye lens 10a: Incident surface of fly-eye lens 10b: Image of outer peripheral surface of fly-eye lens 11: Optical axis 13: Light incident area 14: Wire 15: Position where LED image is imaged 21: Electrode (non-light emission) region)
21b: Image of electrode (non-light emitting region) 22: Light emitting region 22b: Image of light emitting region 30: Rod integrator 30a: Incident surface of rod integrator 30b: Injection surface of rod integrator

Claims (3)

A light source unit that includes multiple LED elements,
The first optical system that narrows the divergence angle of the light emitted from the light source unit without collimating it.
A second optical system that collects the light emitted from the first optical system and
The incident surface is provided with an integrator optical system arranged at the focal position of the second optical system.
A light source device characterized in that the position where an image of the plurality of LED elements is formed is a position shifted to a position before or after the incident surface of the integrator optical system in the optical axis direction . The LED element has a light emitting surface and a linear electrode provided so as to separate the light emitting surface on the side facing the first optical system.
The maximum emission angle of the light ray emitted from the center point of the LED element is θ ₁ , the light source after the light source is emitted from the second optical system is θ ₂ , the width of the electrode is d ₁ , and the light ray is The first is such that the value of L ₁ satisfies the following equation (1), where L ₁ is the length orthogonal to the optical axis when crossing the focal position after the second optical system is ejected. (1) The light source device according to claim 1, wherein the positions of the optical system and the second optical system are adjusted.
2d ₁・ (θ ₁ / θ ₂ ) ≦ L ₁ ≦ 50d ₁・ (θ ₁ / θ ₂ ) ‥‥‥ (1) The light source device according to claim 1 or 2, wherein the integrator optical system is composed of a fly-eye lens in which a plurality of lenses are arranged in a matrix.

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