JP2006066800A - Light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device which is constituted of a plurality of semiconductor lasers for being miniaturized as a device, and can cool the semiconductor lasers and a collimater lens with a simple structure. <P>SOLUTION: The light source device comprises a light guide; a plurality of semiconductor lasers surrounding the outer periphery of the light guide; a casing which has an opening in a light emitting direction, and houses the plurality of semiconductor lasers internally; a collimater lens unit which clogs the opening of the casing, and fixes the light guide so as to expose at least a light entering surface; and a concave surface reflector which reflects a parallel beam which is emitted from the plurality of semiconductor lasers and passes the collimater lens unit to be gathered on the light guide. In an internal space formed with the casing and the collimater lens unit, a cooling medium is filled for cooling the plurality of semiconductor lasers, the collimater lens unit, and the light guide. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light source device that combines light emitted from a plurality of semiconductor lasers with a concave reflecting mirror, and more specifically, includes a plurality of semiconductor lasers, a collimator lens, and a light guide by a cooling medium filled in a casing. The present invention relates to a light source device capable of cooling at the same time.

  In a conventional exposure apparatus, a discharge lamp such as a high-pressure mercury lamp or a metal halide lamp is used as a light source, and light emitted from the discharge lamp is converted into parallel light using, for example, a reflection mirror or a collimator lens. Irradiates the workpiece.

  However, since such a discharge lamp generally has a short service life, it has to be frequently replaced, and there is a problem that the replacement work and the work for adjusting the light quantity after replacement take time and the throughput is low. In addition, the discharge lamp has a problem that it is not economical because of the high power consumption.

In recent years, in order to solve the above problems, instead of a discharge lamp such as a high pressure mercury lamp or a metal halide lamp, a light emitting element such as a semiconductor laser having a longer service life, lower power consumption, and a smaller size. Is being studied as a light source for an exposure apparatus. Since such a semiconductor laser element alone has a small light output, for example, as described in Patent Document 1, it is known to construct a light source device by collecting and combining a plurality of semiconductor lasers.
JP 2002-202442 A JP 2004-6096 A

  However, the technique described in the above publication uses an optical fiber as a light guide after condensing light emitted from a plurality of semiconductor lasers in a light emitting direction by a condensing optical system including a collimator lens and a condensing lens. Are combined and combined. Therefore, it is necessary to provide a considerable distance between each semiconductor laser and the optical fiber according to the distance necessary for condensing by the optical system, and there is a problem that the apparatus becomes large.

  In addition, the collimator lens for making the light emitted from each of the plurality of semiconductor lasers into parallel light is not cooled by a predetermined cooling means, and is thus thermally deteriorated by receiving light from the semiconductor laser, or Problems such as non-uniform temperature occurred. In this case, since the optical characteristics of the collimator lens change, there is a problem that light from all semiconductor lasers cannot be collected on the optical fiber as a light guide.

  Usually, in a light source device including a plurality of semiconductor lasers, it is known that heat generated from the semiconductor laser is radiated by a predetermined means, or the semiconductor laser is cooled by a predetermined means (Patent Document 2). In order to solve the above problems, providing a mechanism for cooling the collimator lens in addition to the cooling means for the semiconductor laser causes an increase in the size of the apparatus and is disadvantageous in terms of cost. This is not preferable.

  The present invention has been made based on the circumstances as described above, and the object thereof is to be able to be downsized as an apparatus even with a plurality of semiconductor lasers, and with a simple structure. An object of the present invention is to provide a light source device capable of cooling a semiconductor laser and a collimator lens.

The present invention includes a light guide, a plurality of semiconductor lasers surrounding the outer periphery of the light guide, a casing having an opening in the light emitting direction, and housing the plurality of semiconductor lasers therein, and an opening of the casing. A collimator lens unit that closes and fixes the light guide so that at least a light incident surface thereof is exposed, and reflects light emitted from the plurality of semiconductor lasers and passed through the collimator lens unit to the light guide. A concave reflecting mirror for condensing,
An internal space formed by the casing and the collimator lens unit is filled with a cooling medium for cooling the plurality of semiconductor lasers, the collimator lens unit, and the light guide.

  Furthermore, the casing has a cooling mechanism for cooling the cooling medium.

  Furthermore, the cooling medium is a fluorine-based inert liquid.

  The light guide is made of a liquid fiber.

  According to the present invention, a light guide, a plurality of semiconductor lasers surrounding the outer periphery of the light guide, a casing having an opening in the light emitting direction and housing the plurality of semiconductor lasers therein, and an opening of the casing A collimator lens unit for closing the light guide and fixing the light guide so that at least a light incident surface thereof is exposed, and reflecting the light emitted from the plurality of semiconductor lasers and passing through the collimator lens unit. A cooling medium for cooling the plurality of semiconductor lasers, the collimator lens unit, and the light guide in an internal space formed by the casing and the collimator lens unit. Compared to conventional light source devices, the optical system By being able to shorten the distance required to condensing Te, it is possible to reduce the size of the light source device. In addition, since the collimator lens is cooled at the same time as the semiconductor laser, the light from all the semiconductor lasers caused by thermal degradation or non-uniform temperature of the collimator lens is collected on the light guide. Since it is possible to surely prevent the problem that light cannot be emitted, the output of the light source device can be increased.

  In addition, the casing is filled with a fluorinated inert liquid as a cooling medium, and a cooling mechanism for efficiently cooling the cooling medium is provided, so that a plurality of semiconductor lasers, collimator lens units, and light guides can be provided. It can be cooled efficiently.

  Furthermore, since the cooling medium is made of a fluorine-based inert liquid having excellent thermal characteristics, the cooling effect on the semiconductor laser, the collimator lens unit, and the light guide is improved, and the fluorine-based inert liquid having a higher refractive index than air. Is present between the semiconductor laser and the collimator lens unit, the surface reflection can be reduced and the transmission loss in the optical system can be reduced.

  And, by using a light guide made of a liquid fiber with a large NA, more semiconductor lasers can be arranged without increasing the focusing distance, so that the output of the light source device can be increased without increasing the size. Can do.

  The light source device of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic view for explaining a light source device of the present invention. FIG. 2 is a diagram for explaining the collimator lens unit.

  The light source device 100 includes a light guide 1, 36 semiconductor lasers 2 arranged in an annular shape so as to surround the outer periphery of the light guide 1, a concave reflecting mirror 3 arranged in the light emitting direction of the semiconductor laser 2, and a semiconductor A casing 4 having an opening in the light emitting direction of the laser 2 and housing the semiconductor laser 2 therein, the light guide 1 is fixed in the vicinity of the center portion, and the casing 4 is spaced from the semiconductor laser 2 at a predetermined interval. A collimator lens unit 5 arranged so as to close the opening of the semiconductor laser 2. In an internal space S formed by the casing 4 and the collimator lens unit 5, the semiconductor laser 2 and the collimator lens unit 5 are provided. A cooling medium 6 for cooling is filled.

  The semiconductor laser 2 used in the light source device 100 has a wavelength range of 350 nm to 450 nm, and emits light having a peak wavelength at, for example, 405 nm. The beam diameter is 4 mm and the maximum output is all common. 30 mW. The material constituting each semiconductor laser 2 is, for example, a gallium nitride (GaN) system. The semiconductor laser 2 is fixed to the casing 4 with its power supply terminal connected to a power supply substrate 8 disposed outside the casing 4 and with its light emitting surface 21 protruding into the internal space S.

The light guide 1 is made of a liquid fiber that transmits light using a light-transmitting high refractive index liquid as a core material. This liquid fiber has a very large NA, for example, 0.6, a large core diameter (quartz is a few hundred microns at most, the liquid is about 1 mm to 5 mm) and a single core, The filling rate can be 100%, and so on.
Such a light guide 1 is fixed to the collimator lens unit 5 so that at least the light incident surface 11 is exposed (not in the internal space S of the casing 4).

The light emitted from the semiconductor laser 2 is reflected by the concave reflecting mirror 3 and enters the light incident surface 11 of the light guide 1. The concave reflecting mirror 3 is made of, for example, quartz glass, calcium fluoride (CaF ₂ ), aluminum, BK7, or the like. The surface of the concave reflecting mirror 3 is coated with, for example, a dielectric multilayer film so that 95% or more of the incident light is reflected to form a reflecting surface. The shape of the reflecting surface of the concave reflecting mirror 3 is preferably an aspherical surface because the propagation characteristics (beam spread) of the horizontal component and the vertical component of the emitted light of the semiconductor laser 2 are different, but may be a spherical surface.

  The casing 4 is made of a highly heat conductive material such as copper (material), for example, from the viewpoint of efficiently cooling the cooling medium 6, and is provided with a cooling mechanism 7 made of, for example, a Peltier element for cooling the cooling medium 6. Yes. The casing 4 has an opening in the light emitting direction of the semiconductor laser 2, and a collimator lens unit 5 is fixed so as to close the opening. A sealed internal space S is formed between the casing 4 and the collimator lens unit 5 by interposing a sealing member 9 such as an O-ring made of silicon resin, for example.

As shown in FIG. 2, the collimator lens unit 5 used in the light source device 100 is formed with a raised curved surface to be a lens portion on one surface of a plate member 51 made of, for example, methacrylic resin (PMMA). It has been done. The 36 lens portions 52 are formed so that the light emitted from one semiconductor laser can be converted into parallel light by one lens portion. By doing so, it is advantageous in terms of the cost required for manufacturing as compared to the case where collimator lenses are prepared independently.
Each lens portion 52 of the collimator lens unit 5 has a common focal length f of 2.75 mm and NA of 0.65, for example.

  The cooling medium 6 filled in the internal space S is a fluorine-based inert liquid (FLUORINERT) (registered trademark) manufactured by 3M. Fluorine-based inert liquids are (1) excellent in thermal properties and have a large heat transfer coefficient, so that heat can be transferred quickly, (2) excellent in electrical insulation, (3) thermochemically stable. It is highly resistant to alteration, (4) inert to constituent materials such as metals, and does not attack metals, and (5) non-flammable, non-toxic, odorless and safe. Therefore, when a fluorine-based inert liquid is used as the cooling medium for the light source device 100, the cooling efficiency of the semiconductor laser, the collimator lens unit, and the light guide is improved, and further, copper that is a constituent material of the casing 4 is used. Does not invade.

  According to the light source device 100 of the present invention as described above, the cooling medium 6 is filled in the internal space S formed between the casing 4 and the collimator lens unit 5, and the cooling medium 6 is cooled in the casing 4. By providing the cooling mechanism 7 for this purpose, the semiconductor laser 2 and the collimator lens unit 5 are in contact with the cooling medium 6 and can be cooled simultaneously. Therefore, it is possible to surely prevent the problem that the light from all the semiconductor lasers cannot be condensed on the light guide, which is caused by the heat deterioration or non-uniform temperature of the collimator lens. Therefore, high output of the light source device can be achieved.

  Further, according to the light source device 100 of the present invention, the structure is such that the emitted light from the semiconductor laser 2 is reflected by the concave reflecting mirror 3 arranged in the light emitting direction and is incident on the light incident surface 11 of the light guide 1. Therefore, the distance required for condensing light by the optical system can be shortened as compared with the conventional light source device, so that the light source device can be downsized.

  Furthermore, since the cooling medium 6 is made of a fluorine-based inert liquid having excellent thermal characteristics, the cooling effect on the semiconductor laser 2 and the collimator lens unit 5 is improved.

  According to the light source device 100 of the present invention, by using a liquid fiber having a large NA, the effective radiation area is expanded without increasing the focal length f, that is, light from a large number of semiconductor lasers is incident on the light guide. There is an effect that light can be condensed on the surface. The reason is considered as follows.

In the following formula (1), S represents the effective radiation area (cm ² ) of the light source, f represents the focal length of the concave reflecting mirror, NA represents the numerical aperture and is a constant.
The light source device 100 using the light guide 1 made of liquid fiber has a large effective radiation area S due to a large NA value, as shown in Expression (1). That is, if a light guide made of a liquid fiber is used, more semiconductor lasers can be arranged without increasing the condensing distance f, so that the output of the light source device can be increased without increasing the size.

For example, the light source device 100 using the light guide 1 made of a liquid fiber has an NA of 0.6 and an effective value calculated by the equation (1) when the focal length of the concave reflecting mirror 3 is 30 mm. The area S is 15.6 cm ² . At this time, since 36 semiconductor lasers having a beam diameter of 4 mm and a maximum output of 30 mW can be arranged, assuming that the loss in the optical system is 5%, 1026 mW (30 mW × 0.95 × 36 = 1026 mW) Output is obtained.
As a comparative example, the light source device 100 using the light guide 1 made of quartz glass has an effective area calculated by Expression (1) when NA is 0.3 and the focal length of the concave reflecting mirror 3 is 30 mm. S is 2.4 cm ² . At this time, since six semiconductor lasers with a beam diameter of 4 mm and a maximum output of 30 mW can be arranged, assuming that the loss in the optical system is 5%, 171 mW (30 mW × 0.95 × 6 = 171 mW) Output is obtained.

  The light guide 1 made of a liquid fiber is reliably cooled by the cooling medium 6 when used in the light source device 100 shown in FIG. Therefore, the problem that the light incident surface 11 is thermally deteriorated by receiving the radiated light from the semiconductor laser 2 does not occur.

The light source device of the present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the light source device 100 of the present invention, the collimator lens unit 5 is not limited to a single member obtained by processing a curved surface to be a lens portion on one plate member as shown in FIG. A member formed by fixing the same number of collimator lenses as the number of semiconductor lasers to the member can also be used.

  Moreover, according to the said embodiment, although 36 semiconductor lasers are used, it is not restricted to this, The number of semiconductor lasers can be changed suitably.

  Furthermore, in the light source device 100 of the present invention, the light guide 1 is not limited to a liquid fiber, and an optical fiber made of, for example, quartz glass can also be used. In this case, the optical fiber made of quartz glass is transparent for light having a wavelength of 200 nm or more, and particularly has a small transmission loss and has a small beam spread for light having a wavelength of 400 nm or more. There is an effect that combined light with high density can be obtained.

It is a figure for demonstrating the light source device of this invention. It is a figure for demonstrating the collimator lens unit which concerns on the light source device of this invention.

Explanation of symbols

1 Light Guide 2 Semiconductor Laser 3 Concave Reflector 4 Casing 5 Collimator Lens Unit 6 Cooling Medium 7 Cooling Mechanism 8 Power Supply Substrate 9 Sealing Member 100 Light Source Device S Internal Space

Claims (4)

A light guide, a plurality of semiconductor lasers surrounding the outer periphery of the light guide, a casing having an opening in the light emitting direction, housing the plurality of semiconductor lasers inside, and closing the opening of the casing; A collimator lens unit for fixing the light guide so that at least its light incident surface is exposed, and a concave surface for reflecting the light emitted from the plurality of semiconductor lasers and passing through the collimator lens unit and condensing on the light guide A reflector, and
A light source device, wherein an internal space formed by the casing and the collimator lens unit is filled with a cooling medium for cooling the plurality of semiconductor lasers, the collimator lens unit, and the light guide. The light source device according to claim 1, wherein the casing includes a cooling mechanism for cooling the cooling medium. The light source device according to claim 1, wherein the cooling medium is a fluorine-based inert liquid. The light source device according to claim 1, wherein the light guide is made of a liquid fiber.

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