Light source device

Abstract

Provided is a light source device which irradiates a fluorescent element with laser light, has high intensity and emits substantially parallel fluorescent light.　Luminous flux from a laser array consisting of vertically and horizontally arranged laser elements is temporarily made into a beam having a uniform luminance distribution, and by means of a first lens array, the beam is then divided into a plurality of beams, which are each condensed and respectively radiated at a plurality of points on one surface of the fluorescent element. The fluorescent element emits fluorescent light having a Lambertian distribution from a plurality of points on the other surface. A second lens array converts the fluorescent light having the Lambertian distribution, emitted from the plurality of points, into substantially parallel light.

Description

light source device

[0001] The present invention relates to a light source device that irradiates a laser beam onto a phosphor element to convert the wavelength of the laser beam and convert the wavelength-converted light into substantially parallel light.

[0002] 2. Description of the Related Art A light source device that converts wavelengths by irradiating one surface of a plate-shaped phosphor element with laser light as excitation light and causing the other surface to emit fluorescent light is known from Patent Document 1 and the like.

[0003] In such a light source device, the intensity of the fluorescence increases depending on the intensity of the light irradiated per unit area of ​​the phosphor element, but when the excitation light intensity per unit area reaches a certain value, the emitted fluorescence intensity saturates. Furthermore, since the size of the area from which fluorescence is emitted from the phosphor element depends on the irradiation size of the excitation light, as the irradiation size of the excitation light increases, it becomes difficult to efficiently capture the fluorescence into a projection optical system, etc.

[0004] In Patent Document 1, multiple laser light sources are arranged vertically and horizontally, and a collimator lens is provided for each laser light source. The collimated multiple light beams are then passed through multiple lenses and a diffuser to form a rectangular light spot of a desired size with a uniform intensity distribution. This rectangular light spot with a uniform intensity distribution is then focused and irradiated onto one point on one surface of a wheel-shaped phosphor element. This causes fluorescence with a uniform intensity distribution to be emitted from a rectangular area on the other surface of the phosphor element.

[0005] Patent document 1 also discloses a projector that irradiates a display element with fluorescent light of a rectangular light spot with a uniform intensity distribution emitted from a phosphor element using lenses and mirrors, and enlarges and projects the image of the display element onto a projection surface.

[0006] International Publication No. 2015 / 189947

[0007] The light source device of Patent Document 1 forms a light spot at one location on a wheel-shaped phosphor element.

[0008] To increase the light output from a light source device, it is necessary to increase the intensity of the light irradiated onto the phosphor element. However, in the configuration of Patent Document 1, which forms a light spot at a single location on the phosphor element, increasing the power of the laser light increases the energy density per unit area of ​​the spot on the phosphor element, causing the location of the phosphor element irradiated with the light spot to become hot, potentially damaging the phosphor element or the substrate. To prevent this, the spot image irradiated onto the phosphor element is enlarged, causing each point within the excitation light spot to emit fluorescence with a Lambertian light distribution. Therefore, the fluorescence generation point is not a point source but a source with a certain area, and due to the etendue law, the beam diameter cannot be reduced no matter how the subsequent optical system is modified.

[0009] Furthermore, the device of Patent Document 1 is configured to irradiate a fluorescent spot onto a display element and project an image on the display element, so the fluorescent light emitted by the phosphor element does not need to be parallel.

[0010] If the light whose wavelength has been converted by the phosphor element can be scanned by a mirror or the like, it can be used as a light source for a scanning fundus camera or a scanning microscope.

[0011] An object of the present invention is to provide a light source device that irradiates a phosphor element with laser light and emits fluorescent light that is high in intensity and approximately parallel.

[0012] To achieve the above object, the present invention provides a light source device including a laser array in which laser elements are arranged vertically and horizontally, a first lens array, plate-shaped phosphor elements that are excited by the wavelength of light emitted by the laser elements and emit fluorescence, and a second lens array. The first lens array includes a predetermined number of condenser lenses. The first lens array splits a beam emitted by the laser array into a predetermined number of beams using the condenser lenses, and focuses each beam using the condenser lenses to irradiate a predetermined number of points on one surface of the phosphor element. The phosphor element emits fluorescence with a Lambertian distribution from points on the other surface opposite to the points where the beams were focused and irradiated by the first lens array. The second lens array includes a predetermined number of collimator lenses. The collimator lenses are arranged so that their optical axes coincide with the emission points of the fluorescence on the other surface of the phosphor element, and convert the fluorescence with a Lambertian distribution emitted from the emission points into approximately parallel light.

[0013] According to the present invention, it is possible to provide an apparatus that irradiates a phosphor element with laser light and emits fluorescent light, the apparatus emitting fluorescent light that is high in intensity and is substantially parallel.

[0014] 1A and 1B are explanatory diagrams of a light source device according to an embodiment of the present invention as viewed from the X-axis direction and the Y-axis direction, respectively; an explanatory diagram showing spot images on a phosphor element 40 of the light source device according to an embodiment; a block diagram showing the configuration of a first lens array 30, a phosphor element 40, and a second lens array 50 of the light source device according to an embodiment; and (a) and (b) are diagrams showing an example of a light source module using the light source device according to an embodiment. A block diagram showing a light source device of a comparative example.

[0015] A light source device according to one embodiment of the present invention will be described below.

[0016] 1A and 1B are views of the light source device 1 of this embodiment as viewed from the X-axis direction and the Y-axis direction, respectively, Fig. 2 is a diagram showing a light spot image on a phosphor element, and Fig. 3 is a diagram showing light rays from the first lens array, the phosphor element, and the second lens array.

[0017] As shown in Figures 1(a) and (b), the light source device 1 of this embodiment is configured to include a laser array 10 in which laser elements are arranged vertically and horizontally (Y and X axis directions), a first lens system 20, a first lens array 30, phosphor elements 40, and a second lens array 50.

[0018] The laser array 10 includes a lens array module (not shown) in addition to the laser elements, and converts the laser light emitted by each laser element into parallel light and emits it.

[0019] The phosphor elements 40 are plate-shaped elements that emit fluorescence when excited by the wavelength of light emitted by the laser elements of the laser array 10. For example, plate-shaped phosphor ceramic, phosphor glass, or the like can be used as the phosphor elements 40. The phosphor elements 40 may include a substrate that transmits the wavelength of light emitted by the laser elements and the fluorescence.

[0020] The arrangement of the laser elements of the laser array 10 in the Y and X axis directions is, for example, 5 x 4. The arrangement of the condenser lenses of the first lens array 30 and the collimator lenses of the second lens array 50 in the Y and X axis directions is, for example, 5 x 2.

[0021] The first lens system 20 includes a fly-eye lens 21 , a first cylindrical lens 22 , and a second cylindrical lens 23 .

[0022] The fly-eye lens 21 divides and superimposes the laser light emitted from the laser array 10 to form a beam with a uniform brightness distribution. The first cylindrical lens 22 and the second cylindrical lens 23 reduce the range of the laser light group emitted from the laser array 10 to correspond to the size of the incident surface of the first lens array 30.

[0023] 3, the first lens array 30 includes a predetermined number (N=10) of condenser lenses 31. The first lens array 30 splits the beam 120 emitted from the first lens system 20 into the same number of beams 131 as the predetermined number (N) by the condenser lenses 31, and each of the split beams 131 is condensed by the condenser lenses 31 to form spot images at N points 41 on one surface 40 a of the phosphor element 40.

[0024] As a result, the phosphor element 40 emits fluorescent light 142 with a Lambertian distribution from a point 42 opposite to the point 41 where the spot image is formed on the surface 40b opposite the surface 40a.

[0025] The second lens array 50 includes N collimating lenses 51. The collimating lenses 51 are arranged so that the optical axes 51a of the respective collimating lenses 51 coincide with the emission points 42 of the fluorescence 142 on the surfaces 40b of the phosphor elements 40. As a result, the second lens array 50 converts the fluorescence 142 with a Lambertian distribution emitted from the emission points 42 into approximately parallel light 143.

[0026] At this time, the lens effective diameter 51b of the multiple collimator lenses 51 of the second lens array 50 is designed to be a size that allows a predetermined percentage (e.g., 70%) or more of the Lambertian-distributed fluorescence 142 emitted from the emission point 42 to be incident.

[0027] Furthermore, the spacing 51c between the plurality of collimator lenses 51 of the second lens array 50 is designed to be equal to or larger than the effective lens diameter 51b.

[0028] The intervals between the points 41 onto which the plurality of condenser lenses 31 of the first lens array 30 irradiate light are designed to match the intervals between the collimator lenses 51 of the second lens array 50 .

[0029] 3, for convenience of illustration, the N collimating lenses 51 of the second lens array 50 are depicted as not being connected to one another, but in reality, the N collimating lenses 51 are connected to one another in the second lens array 50. Similarly, the N condensing lenses 31 of the first lens array 30 are also actually connected to one another.

[0030] In the light source device 1 of this embodiment configured as described above, the light emitted from the laser array 10 is converted into parallel light beams in the Z-axis direction by the lens array module provided in the laser array 10, the number of which corresponds to the number of laser elements. The parallel light beams are then converted into a rectangular beam 120 with a substantially uniform luminance distribution by the fly-eye lens 21 and cylindrical lenses 22 and 23.

[0031] The first lens array 30 forms spot images at points 41 on the surface 40 a of the phosphor element 40 , the number of which is equal to the number (N) of lenses that make up the first lens array 30 .

[0032] As a result, the laser power has an intensity divided by the number of spot images, so that the energy per unit area on the phosphor can be reduced.

[0033] Furthermore, before being split by the first lens array 30, the beam is split and superimposed by the fly-eye lens 21 to form the beam 120, so the luminance distribution of the beam 120 is averaged and uniform. Therefore, the beam 131 obtained by splitting and converging the beam 120 also has a uniform luminance distribution, and the luminance of the spot image of the point 41 on the phosphor element 40 is also averaged.

[0034] The phosphor element 40 emits fluorescent light 142 with a Lambertian distribution from a point 42 opposite to the point 41 .

[0035] The fluorescent light 142 emitted from the phosphor element 40 is condensed by the second lens array 50 and converted into, for example, two substantially parallel beams of light 143 .

[0036] Thereafter, the two substantially parallel beams 143 are guided to the twin lens 60 and combined, as shown in FIGS. 4( a ) and 4 ( b ), and are then emitted from the light source device 1 after passing through the aperture 70 .

[0037] The reduction ratio of the cylindrical lenses 22 and 23 can be set appropriately depending on the size of the incident surface of the first lens array 30. If reduction is required in only one direction, only one of them may be used.

[0038] It is also possible to configure the system without the dichroic mirrors 1 and 2 and the diaphragm #4 shown in FIGS.

[0039] As described above, the light source device 1 of this embodiment has high power when the laser beams emitted from the multiple laser elements are superimposed. However, the high-power laser beam is not irradiated directly onto the phosphor element 40, but is instead split into multiple beams 131 by the first lens array 30 and irradiated. This makes it possible to reduce the light energy per unit area of ​​the light spot image irradiated onto the point 41 of the phosphor element 40. Therefore, the light can be converted into fluorescent light 142 with high efficiency without saturating the phosphor element 40, emitted, and converted into a beam of approximately parallel light 143 by the second lens array 50. Therefore, the light source device 1 of this embodiment is capable of emitting a beam of high-brightness and approximately parallel light 143.

[0040] The beam of the substantially parallel light 143 has a high degree of parallelism, so that by converging it with a lens, it is possible to narrow the beam diameter to a size equivalent to the spot diameter on the phosphor element 40 .

[0041] 5 shows an example of a comparative example in which beams from multiple laser elements in a CAN package are not combined into one uniform beam, but are individually focused onto a phosphor element 540 to irradiate a light spot image 541. This configuration can disperse the spot image on the phosphor element 540, and can increase the overall light amount (luminous flux) without increasing the energy density per unit area of ​​the light spot image 541 on the phosphor element 540.

[0042] However, the CAN-packaged laser element itself is physically large, measuring approximately 3 mm in diameter as a package. If multiple CAN packages were arranged to form a laser array, the spacing between beams would be 3 mm or more, which would require a correspondingly large first lens system.

[0043] Furthermore, even if a single lens 501 is provided to collimate the light emitted from the phosphor element 540, the light will still be divergent, making it difficult to collimate the light in the device structure of the comparative example shown in FIG.

[0044] <Modifications of the embodiment> A modification of the embodiment will be described. The plate-shaped phosphor element 40 of the light source device 1 in Fig. 1 may have a structure in which the area of ​​the main plane is divided into a plurality of regions, and each region is made of one of two or more types of phosphor. For example, a structure in which a portion of the area of ​​the main plane of the phosphor element 40 is made of a yellow phosphor and the remaining region is made of a green phosphor may be used.

[0045] By using such phosphor elements 40 that combine two or more types of phosphors, it is possible to emit fluorescence from each of the regions of the multiple types of phosphors while using the laser array 10 in which laser elements of a single wavelength are arranged. This makes it possible to emit parallel light that is a mixture of fluorescence of multiple wavelengths. This allows the wavelength band of the light emitted by the light source device 1 to be broadened.

[0046] The light source device of this embodiment can be used as various light source modules that require approximately parallel light after wavelength conversion by a phosphor. For example, the light source device of this embodiment can be suitably used as a light source that scans approximately parallel light, such as a light source module for a scanning fundus camera or a light source module for a scanning microscope.

[0047] REFERENCE SIGNS LIST 1 Light source device 10 Laser array 20 First lens system 21 Fly's eye lens 22 First cylindrical lens 23 Second cylindrical lens 30 First lens array 31 Condenser lens 40 Phosphor element 40a Surface 40b Surface 41 Point 42 Point 50 Second lens array 51 Collimator lens 51a Optical axis 51b Lens effective diameter 51c Distance between collimator lenses 120 Beam 131 Beam 142 Fluorescent light 143 Approximately parallel light 541 Light spot image

Claims

1. A laser array having laser elements arranged vertically and horizontally, a first lens array, plate-shaped phosphor elements that are excited by the wavelength of light emitted by the laser elements and emit fluorescence, and a second lens array, wherein the first lens array includes a predetermined number of condenser lenses, and the first lens array divides the beams emitted by the laser array into the same number of beams as the predetermined number using the condenser lenses, and condenses each of the beams using the condenser lenses to irradiate the same number of points on one surface of the phosphor elements, the number of points being the same as the predetermined number, and the phosphor elements emit fluorescence with a Lambertian distribution from points on the other surface opposite to the one surface that are irradiated by the beams condensed by the first lens array, the second lens array includes the same number of collimating lenses as the predetermined number, and the collimating lenses are arranged so that their optical axes coincide with the emission points of the fluorescence on the other surface of the phosphor element, and the fluorescence having a Lambertian distribution emitted from the emission points is converted into approximately parallel light.

2. A light source device according to claim 1, characterized in that a first lens system is disposed between the laser array and the lens array, which converts the multiple beams emitted from the multiple laser elements of the laser array into beams with a uniform brightness distribution.

3. A light source device according to claim 2, characterized in that the first lens system has the function of reducing the range of the laser light emitted from the laser array that is irradiated onto the lens array.

4. A light source device according to claim 1, characterized in that the effective lens diameter of the plurality of collimating lenses of the second lens array is a size that allows a predetermined percentage or more of the fluorescence having a Lambertian distribution emitted from the fluorescence emission point to be incident, and the spacing between the plurality of collimating lenses of the second lens array is set to be equal to or greater than the effective lens diameter.

5. A light source device according to claim 1, characterized in that the spacing between the points at which the light of the plurality of condenser lenses of the first lens array is irradiated is equal to the spacing between the collimator lenses of the second lens array.

6. A light source device according to claim 2, wherein said first lens system includes a fly's eye lens and a cylindrical lens.

7. A light source device according to claim 1, characterized in that the phosphor element has a main surface divided into a plurality of regions, and the plurality of regions are made of one of two or more different types of phosphors.

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