JP4014990B2 - Optical fiber connection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for connecting optical fibers, and more particularly to a method for connecting two optical fibers having different clad diameters.
[0002]
[Prior art]
Conventionally, various optical fibers in which a core is covered with a clad having a lower refractive index are widely used as means for propagating light such as laser light. A plurality of optical fibers are often used to form a so-called fiber bundle to propagate a large amount of light. When a fiber bundle is configured in this way, there is a demand for arranging a larger number of optical fibers at a high density at the light emitting end or the light incident end.
[0003]
Therefore, conventionally, as disclosed in, for example, Patent Document 1, it has been considered that the cladding is thinly processed at each one end portion of the plurality of optical fibers, and the thinly processed one end portions are arranged in close contact with each other. In order to process the clad as described above, in Patent Document 1, it is proposed to etch one end of the optical fiber with hydrofluoric acid.
[0004]
[Patent Document 1]
Japanese Patent No. 2801329
[0005]
[Problems to be solved by the invention]
However, the above-mentioned hydrofluoric acid is a dangerous chemical that melts the glass, so it needs to be handled with care. Therefore, the processing of the optical fiber with hydrofluoric acid is not good. Yes.
[0006]
Therefore, it is conceivable to connect another optical fiber having a smaller cladding diameter to the tip of the optical fiber normally used for light propagation and to bundle the optical fiber portion having the smaller cladding diameter. . In order to connect the two optical fibers in this way, conventionally, a discharge-type fusion splicer is widely used in which one end portions of the two optical fibers are coaxially aligned and fusion-bonded.
[0007]
However, when two optical fibers having a large difference in outer diameter (cladding diameter) are fusion spliced in this way, if the discharge conditions are set so that the thicker optical fiber melts appropriately, the thinner optical fiber May melt too much and the tip may be rounded, and the two optical fibers may not be properly fusion spliced. On the other hand, if the discharge conditions are set so that the thin optical fiber can be melted appropriately, the thick optical fiber will not melt because the discharge is weak, and in this case as well, both optical fibers will be in close contact and melt properly. Incoming connection may not be possible. In the case of this conventional method, specifically, a loss of about 1 dB occurs in this connection portion, and the connection efficiency may remain at about 80%.
[0008]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a method capable of reliably connecting two optical fibers having a large difference in outer diameter.
[0010]
[Means for Solving the Problems]
Book No. by invention 1 The optical fiber connection method of
The In a method of connecting two optical fibers having different lad diameters,
A clad at one end of an optical fiber having a large clad diameter, The diameter of the end face is Intermediate diameter between the clads of both optical fibers To be To process
An optical fiber having a small cladding diameter is fused to one end of the processed optical fiber.
[0011]
In addition, according to the present invention 2 The optical fiber connection method of
Similarly, in a method of connecting two optical fibers having different clad diameters,
An optical fiber having a large cladding diameter and an optical fiber having a small cladding diameter are fused to one end and the other end of an optical fiber having an intermediate cladding diameter of these optical fibers, respectively. Is.
[0012]
【The invention's effect】
In the first optical fiber connecting method according to the present invention, the cladding at one end of the optical fiber having a large cladding diameter is processed to have a diameter substantially the same as the cladding diameter of the optical fiber having a small cladding diameter. Since an optical fiber having a small cladding diameter is fused to one end of the optical fiber, the fusion splicing is performed between optical fibers having substantially the same cladding diameter. Therefore, the optical fiber with the smaller outer diameter may melt too much, or the optical fiber with the larger outer diameter may not melt, as in the case of fusion splicing between optical fibers with greatly different outer diameters. Therefore, both optical fibers can be easily and reliably connected.
[0013]
In the second optical fiber connecting method according to the present invention, the clad at one end of the optical fiber having a large clad diameter is processed into an intermediate diameter between both optical fibers, and the processed optical fiber is processed. Since an optical fiber having a small clad diameter is fused to one end of the optical fiber, the fusion splicing is performed between optical fibers whose clad diameters are not significantly different. Therefore, even in this method, the optical fiber with the smaller outer diameter is melted too much, or the optical fiber with the larger outer diameter is not melted, as in the case of fusion splicing of optical fibers having greatly different outer diameters. Therefore, both optical fibers can be easily and reliably connected.
[0014]
In the third optical fiber connecting method according to the present invention, an optical fiber having a large cladding diameter and an optical fiber having a small cladding diameter are interposed between optical fibers having intermediate cladding diameters. Since the fusion-splicing is performed, an optical fiber having an intermediate cladding diameter and an optical fiber having a large cladding diameter are fused and an optical fiber having an intermediate cladding diameter is small. The fusion splicing with a certain optical fiber is made between optical fibers whose clad diameters do not differ greatly. Therefore, even in this method, the optical fiber with the smaller outer diameter is melted too much, or the optical fiber with the larger outer diameter is not melted, as in the case of fusion splicing of optical fibers having greatly different outer diameters. Thus, each optical fiber can be easily and reliably connected.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
FIG. 29 illustrates an optical fiber connection method according to an embodiment of the present invention. In this example, as shown in the figure, as an example, the multimode optical fiber 31 having an outer diameter (cladding diameter) of 60 μm, which is smaller than that at the tip of the multimode optical fiber 30 having an outer diameter (cladding diameter) of 125 μm. Connect. The multimode optical fiber 30 is a step index type optical fiber as an example, and a core 30a is covered with a clad 30b having a lower refractive index than that of the core 30a. Similarly, in the multimode optical fiber 31, the core 31a is covered with a clad 31b having a lower refractive index.
[0017]
The multimode optical fiber 30 has a clad diameter = 125 μm, a core diameter = 50 μm, NA = 0.2, the transmittance of the incident end face coat = 99.5% or more, and the multimode optical fiber 31 has a clad diameter = 60 μm, Core diameter = 50 μm, NA = 0.2.
[0018]
First, as shown in FIG. 2A, the cladding 30b at the tip of the multimode optical fiber 30 is subjected to machining such as polishing to form a small diameter portion 30c having a length of about 1 mm, for example. The outer diameter of the small diameter portion 30 c is 60 μm, which is equal to the cladding diameter of the multimode optical fiber 31.
[0019]
Next, as shown in FIG. 2B, the multi-mode optical fiber 31 having the same outer diameter is fused and connected to the tip of the small diameter portion 30c so that the core axes are aligned coaxially. For this fusion, a general discharge-type fusion splicer conventionally used for fusion of this type of optical fiber may be used. As such an optical fiber fusion splicer, for example, a small core direct view type optical fiber fusion splicer SUMIOFCAS “Type-37” manufactured by Sumitomo Electric Industries, Ltd. may be mentioned.
[0020]
As described above, in the method of the present embodiment, the small-diameter portion 30c is formed at the distal end portion of the multimode optical fiber 30, and then the multimode optical fiber 31 having the same outer diameter is fused and connected to the small diameter portion 30c. Therefore, the optical fiber 31 with the smaller outer diameter is melted too much, or the optical fiber 30 with the larger outer diameter is not melted, as in the case of fusion splicing of optical fibers having greatly different outer diameters. Therefore, both optical fibers 30 and 31 can be connected easily and reliably. Specifically, the loss at the connection portion between both optical fibers 30 and 31 can be suppressed to about 0.05 dB, and a connection efficiency of 99% can be realized.
[0021]
As will be described later, a plurality of optical fibers formed by connecting both optical fibers 30 and 31 are prepared, and the tip portions of these optical fibers 31 are bundled and used. That is, since the small-diameter portion 30c at the tip of the optical fiber 30 is not bundled, the machining accuracy required for the small-diameter portion 30c is not so high, and the small-diameter portion 30c can be easily formed.
[0022]
Next, referring to FIG. 30, an optical fiber connecting method according to another embodiment of the present invention will be described. In FIG. 30, the same elements as those in FIG. 29 are denoted by the same reference numerals, and description thereof will be omitted unless necessary (the same applies hereinafter).
[0023]
In this embodiment, the cladding 30b at the tip of the multimode optical fiber 30 is subjected to mechanical processing such as polishing to form a small diameter portion 30c ′ having a length of about 1 mm, for example. The outer diameter of the small diameter portion 30c ′ is set to 80 μm, which is slightly larger than the clad diameter of 60 μm of the multimode optical fiber 31. Next, the multi-mode optical fiber 31 having a slightly smaller outer diameter is fused and connected to the tip of the small-diameter portion 30c ′ so that the core axes are coaxially aligned with each other.
[0024]
Even in the above-described manner, the optical fiber 31 with the smaller outer diameter is melted as in the case where the multimode optical fiber 31 having a greatly different outer diameter is fused and connected directly to the tip of the multimode optical fiber 30. The optical fiber 30 having a larger outer diameter is not melted, and the both optical fibers 30 and 31 can be easily and reliably connected.
[0025]
Next, with reference to FIG. 31, an optical fiber connecting method according to still another embodiment of the present invention will be described. In this embodiment, first, the multimode optical fiber 32 having an outer diameter smaller than that and larger than the multimode optical fiber 31 and having an outer diameter of 80 μm is fusion spliced to the tip of the multimode optical fiber 30. To do. Next, the multimode optical fiber 31 having an outer diameter smaller than that of the multimode optical fiber 32 having the intermediate diameter is fused and connected.
[0026]
As described above, when the multimode optical fiber 32 whose outer diameter is not significantly different from the multimode optical fiber 30 is fusion-spliced, the optical fiber 32 having the smaller outer diameter is melted excessively, or conversely. When the multimode optical fiber 31 whose outer diameter is not greatly different from the multimode optical fiber 32 is fused without splicing the optical fiber 30 with the larger outer diameter, The optical fiber 31 with the smaller outer diameter is not melted excessively, and the optical fiber 32 with the larger outer diameter is not melted. As a result, both optical fibers 30 and 31 can be connected easily and reliably. It becomes.
[0027]
In contrast to the above, the optical fiber 31 and the optical fiber 32 may be fused and then the optical fiber 30 and the optical fiber 32 may be fused and connected. The effect is obtained.
[0028]
Next, an example of an exposure apparatus using a multimode optical fiber connected by the method of the present invention will be described.
[0029]
[Configuration of exposure apparatus]
As shown in FIG. 1, the exposure apparatus of this example includes a flat stage 152 that holds a sheet-like photosensitive material 150 by adsorbing to the surface. Two guides 158 extending along the stage moving direction are installed on the upper surface of the thick plate-shaped installation table 156 supported by the four legs 154. The stage 152 is arranged so that the longitudinal direction thereof faces the stage moving direction, and is supported by a guide 158 so as to be reciprocally movable. The exposure apparatus is provided with a drive device (not shown) for driving the stage 152 along the guide 158.
[0030]
A U-shaped gate 160 is provided at the center of the installation table 156 so as to straddle the movement path of the stage 152. Each of the ends of the U-shaped gate 160 is fixed to both side surfaces of the installation table 156. A scanner 162 is provided on one side of the gate 160, and a plurality of (for example, two) detection sensors 164 for detecting the front and rear ends of the photosensitive material 150 are provided on the other side. The scanner 162 and the detection sensor 164 are respectively attached to the gate 160 and fixedly arranged above the moving path of the stage 152. The scanner 162 and the detection sensor 164 are connected to a controller (not shown) that controls them.
[0031]
As shown in FIGS. 2 and 3B, the scanner 162 includes a plurality of (for example, 14) exposure heads 166 arranged in an approximately matrix of m rows and n columns (for example, 3 rows and 5 columns). ing. In this example, four exposure heads 166 are arranged in the third row in relation to the width of the photosensitive material 150. In the case where individual exposure heads arranged in the m-th row and the n-th column are shown, the exposure head 166 is used. _mn Is written.
[0032]
An exposure area 168 by the exposure head 166 has a rectangular shape with a short side in the sub-scanning direction. Therefore, as the stage 152 moves, a strip-shaped exposed area 170 is formed for each exposure head 166 in the photosensitive material 150. In addition, when showing the exposure area by each exposure head arranged in the mth row and the nth column, the exposure area 168 is shown. _mn Is written.
[0033]
Further, as shown in FIGS. 3A and 3B, each of the exposure heads in each row arranged in a line so that the strip-shaped exposed areas 170 are arranged without gaps in the direction orthogonal to the sub-scanning direction. These are arranged with a predetermined interval (natural number times the long side of the exposure area, twice in this example) in the arrangement direction. Therefore, the exposure area 168 in the first row ₁₁ And exposure area 168 ₁₂ The portion that cannot be exposed between the exposure area 168 and the exposure area 168 in the second row _{twenty one} And exposure area 168 in the third row ₃₁ And can be exposed.
[0034]
Exposure head 166 ₁₁ ~ 166 _mn As shown in FIGS. 4, 5 (A) and 5 (B), each of them is a digital micromirror device (spatial light modulation element that modulates an incident light beam for each pixel according to image data. DMD) 50. The DMD 50 is connected to a controller (not shown) including a data processing unit and a mirror drive control unit. The data processing unit of this controller generates a control signal for driving and controlling each micromirror in the region to be controlled by the DMD 50 for each exposure head 166 based on the input image data. The area to be controlled will be described later. The mirror drive control unit controls the angle of the reflection surface of each micromirror of the DMD 50 for each exposure head 166 based on the control signal generated by the image data processing unit. The control of the angle of the reflecting surface will be described later.
[0035]
On the light incident side of the DMD 50, a fiber array light source 66 including a laser emitting section in which emission ends (light emitting points) of an optical fiber are arranged in a line along a direction corresponding to the long side direction of the exposure area 168, a fiber A lens system 67 for correcting the laser light emitted from the array light source 66 and condensing it on the DMD, and a mirror 69 for reflecting the laser light transmitted through the lens system 67 toward the DMD 50 are arranged in this order.
[0036]
The lens system 67 includes a pair of combination lenses 71 that collimate the laser light emitted from the fiber array light source 66 and a pair of combination lenses that correct the light quantity distribution of the collimated laser light to be uniform. 73 and a condensing lens 75 that condenses the laser light whose light quantity distribution is corrected on the DMD. With respect to the arrangement direction of the laser emitting ends, the combination lens 73 spreads the light beam at a portion close to the optical axis of the lens and contracts the light beam at a portion away from the optical axis, and with respect to a direction orthogonal to the arrangement direction. Has a function of allowing light to pass through as it is, and corrects the laser light so that the light quantity distribution is uniform.
[0037]
Further, on the light reflection side of the DMD 50, lens systems 54 and 58 for forming an image of the laser light reflected by the DMD 50 on the scanning surface (exposed surface) 56 of the photosensitive material 150 are arranged. The lens systems 54 and 58 are arranged so that the DMD 50 and the exposed surface 56 are in a conjugate relationship.
[0038]
As shown in FIG. 6, the DMD 50 is configured such that a micromirror 62 is supported by a support column on an SRAM cell (memory cell) 60, and a large number of (pixels) (pixels) are formed. For example, the mirror device is configured by arranging 600 × 800 micromirrors in a lattice pattern. Each pixel is provided with a micromirror 62 supported by a support column at the top, and a material having a high reflectance such as aluminum is deposited on the surface of the micromirror 62. The reflectance of the micromirror 62 is 90% or more. A silicon gate CMOS SRAM cell 60 manufactured in a normal semiconductor memory manufacturing line is disposed directly below the micromirror 62 via a support including a hinge and a yoke, and is entirely monolithic (integrated type). ).
[0039]
When a digital signal is written in the SRAM cell 60 of the DMD 50, the micromirror 62 supported by the support is inclined within a range of ± α degrees (for example, ± 10 degrees) with respect to the substrate side on which the DMD 50 is disposed with the diagonal line as the center. It is done. FIG. 7A shows a state in which the micromirror 62 is tilted to + α degrees in the on state, and FIG. 7B shows a state in which the micromirror 62 is tilted to −α degrees in the off state. Therefore, by controlling the inclination of the micromirror 62 in each pixel of the DMD 50 as shown in FIG. 6 according to the image signal, the light incident on the DMD 50 is reflected in the inclination direction of each micromirror 62. .
[0040]
FIG. 6 shows an example of a state in which a part of the DMD 50 is enlarged and the micromirror 62 is controlled to + α degrees or −α degrees. On / off control of each micromirror 62 is performed by a controller (not shown) connected to the DMD 50. A light absorber (not shown) is arranged in the direction in which the light beam is reflected by the micromirror 62 in the off state.
[0041]
Further, it is preferable that the DMD 50 is disposed with a slight inclination so that the short side forms a predetermined angle θ (for example, 1 ° to 5 °) with the sub-scanning direction. 8A shows the scanning trajectory of the reflected light image (exposure beam) 53 by each micromirror when the DMD 50 is not tilted, and FIG. 8B shows the scanning trajectory of the exposure beam 53 when the DMD 50 is tilted. Show.
[0042]
In the DMD 50, a number of micromirror arrays in which a large number (for example, 800) of micromirrors are arranged in the longitudinal direction are arranged in a large number (for example, 600 sets) in the short direction. As shown, the pitch P of the scanning trajectory (scanning line) of the exposure beam 53 by each micromirror is obtained by inclining the DMD 50. ₁ However, the pitch P of the scanning line when the DMD 50 is not inclined. ₂ It becomes narrower and the resolution can be greatly improved. On the other hand, since the tilt angle of the DMD 50 is very small, the scanning width W when the DMD 50 is tilted. ₂ And the scanning width W when the DMD 50 is not inclined. ₁ Is substantially the same.
[0043]
Further, the same scanning line is overlapped and exposed (multiple exposure) by different micromirror rows. In this way, by performing multiple exposure, it is possible to control a minute amount of the exposure position and to realize high-definition exposure. Further, joints between a plurality of exposure heads arranged in the main scanning direction can be connected without a step by controlling a very small amount of exposure position.
[0044]
Note that the same effect can be obtained by arranging the micromirror rows in a staggered manner by shifting the micromirror rows by a predetermined interval in a direction orthogonal to the sub-scanning direction instead of inclining the DMD 50.
[0045]
As shown in FIG. 9A, the fiber array light source 66 includes a plurality of (for example, six) laser modules 64, and one end of the multimode optical fiber 30 is coupled to each laser module 64. Yes. The other end of the multimode optical fiber 30 is coupled with an optical fiber 31 having the same core diameter as the multimode optical fiber 30 and a cladding diameter smaller than the multimode optical fiber 30, as shown in FIG. A laser emission portion 68 is configured by arranging the emission end portions (light emission points) of the optical fiber 31 in one row along the main scanning direction orthogonal to the sub-scanning direction. As shown in FIG. 9D, the light emitting points can be arranged in two rows along the main scanning direction.
[0046]
As shown in FIG. 9B, the emission end of the optical fiber 31 is sandwiched and fixed between two support plates 65 having a flat surface. Further, a transparent protective plate 63 such as glass is disposed on the light emitting side of the optical fiber 31 in order to protect the end face of the optical fiber 31. The protective plate 63 may be disposed in close contact with the end surface of the optical fiber 31 or may be disposed so that the end surface of the optical fiber 31 is sealed. The light emitting end portion of the optical fiber 31 has a high light density and is likely to collect dust and easily deteriorate. However, by disposing the protective plate 63, it is possible to prevent the dust from adhering to the end face and to delay the deterioration.
[0047]
In this example, in order to arrange the emission ends of the optical fibers 31 with a small cladding diameter in a line without any gaps, the multimode optical fiber 30 is placed between two adjacent multimode optical fibers 30 at a portion with a large cladding diameter. Two exit ends of the optical fiber 31 coupled to the two multimode optical fibers 30 adjacent to each other at the portion where the cladding diameter is large are the exit ends of the optical fiber 31 coupled to the stacked and stacked multimode optical fibers 30. Are arranged so as to be sandwiched between them.
[0048]
As shown in FIG. 10, in this optical fiber, a small diameter portion 30c is formed at a tip portion on the laser light emission side of a multimode optical fiber 30 having a large cladding diameter, and a cladding having a length of 1 to 30 cm is formed in the small diameter portion 30c. An optical fiber 31 having a small diameter is coupled coaxially, and is formed by the method described above with reference to FIG. Here, the diameter of the core 31 a of the optical fiber 31 is the same as the diameter of the core 30 a of the multimode optical fiber 30. Hereinafter, the optical fiber 31 may be referred to as an emission end portion of the multimode optical fiber 30.
[0049]
The multimode optical fiber 30 and the optical fiber 31 may be any of a step index type optical fiber, a graded index type optical fiber, and a composite type optical fiber. For example, a step index type optical fiber manufactured by Mitsubishi Cable Industries, Ltd. can be used. In this example, the multimode optical fiber 30 and the optical fiber 31 are step index type optical fibers. The multimode optical fiber 30 has a cladding diameter = 125 μm, a core diameter = 50 μm, NA = 0.2, and an incident end face coating. The transmittance is 99.5% or more, and the optical fiber 31 has a cladding diameter = 60 μm, a core diameter = 50 μm, and NA = 0.2.
[0050]
In general, in the laser light in the infrared region, the propagation loss increases as the cladding diameter of the optical fiber is reduced. For this reason, a suitable cladding diameter is determined according to the wavelength band of the laser beam. However, the shorter the wavelength, the smaller the propagation loss. In the case of laser light having a wavelength of 405 nm emitted from a GaN-based semiconductor laser, the cladding thickness {(cladding diameter−core diameter) / 2} is set to an infrared light having a wavelength band of 800 nm. The propagation loss hardly increases even if it is about ½ of the case of propagating infrared light and about ¼ of the case of propagating infrared light in the 1.5 μm wavelength band for communication. Therefore, the cladding diameter can be reduced to 60 μm.
[0051]
However, the cladding diameter of the optical fiber 31 is not limited to 60 μm. The clad diameter of the optical fiber used in the conventional fiber light source is 125 μm, but the depth of focus becomes deeper as the clad diameter becomes smaller. Therefore, the clad diameter of the multimode optical fiber is preferably 80 μm or less, more preferably 60 μm or less. Preferably, it is 40 μm or less. On the other hand, since the core diameter needs to be at least 3 to 4 μm, the cladding diameter of the optical fiber 31 is preferably 10 μm or more.
[0052]
The laser module 64 is configured by a combined laser light source (fiber light source) shown in FIG. This combined laser light source includes a plurality of (for example, seven) chip-like lateral multimode or single mode GaN-based semiconductor lasers LD1, LD2, LD3, LD4, LD5, LD6, arrayed and fixed on the heat block 10. And LD7, collimator lenses 11, 12, 13, 14, 15, 16, and 17 provided corresponding to each of the GaN-based semiconductor lasers LD1 to LD7, one condenser lens 20, and one multi-lens. Mode optical fiber 30. The number of semiconductor lasers is not limited to seven. For example, as many as 20 semiconductor laser beams can be incident on a multimode optical fiber having a cladding diameter = 60 μm, a core diameter = 50 μm, and NA = 0.2. In addition, the number of optical fibers can be further reduced.
[0053]
The GaN-based semiconductor lasers LD1 to LD7 all have the same oscillation wavelength (for example, 405 nm), and the maximum output is also all the same (for example, 100 mW for the multimode laser and 30 mW for the single mode laser). As the GaN-based semiconductor lasers LD1 to LD7, lasers having an oscillation wavelength other than the above 405 nm in a wavelength range of 350 nm to 450 nm may be used.
[0054]
As shown in FIGS. 12 and 13, the above-described combined laser light source is housed in a box-shaped package 40 having an upper opening together with other optical elements. The package 40 includes a package lid 41 created so as to close the opening thereof. After the deaeration process, a sealing gas is introduced, and the package 40 and the package lid 41 are closed by closing the opening of the package 40 with the package lid 41. 41. The combined laser light source is hermetically sealed in a closed space (sealed space) formed by 41.
[0055]
A base plate 42 is fixed to the bottom surface of the package 40, and the heat block 10, a condensing lens holder 45 that holds the condensing lens 20, and the multimode optical fiber 30 are disposed on the top surface of the base plate 42. A fiber holder 46 that holds the incident end is attached. The exit end of the multimode optical fiber 30 is drawn out of the package from an opening formed in the wall surface of the package 40.
[0056]
Further, a collimator lens holder 44 is attached to the side surface of the heat block 10, and the collimator lenses 11 to 17 are held. An opening is formed in the lateral wall surface of the package 40, and wiring 47 for supplying a driving current to the GaN-based semiconductor lasers LD1 to LD7 is drawn out of the package through the opening.
[0057]
In FIG. 13, in order to avoid complication of the drawing, only the GaN semiconductor laser LD7 among the plurality of GaN semiconductor lasers is numbered, and only the collimator lens 17 among the plurality of collimator lenses is numbered. is doing.
[0058]
FIG. 14 shows the front shape of the attachment part of the collimator lenses 11-17. Each of the collimator lenses 11 to 17 is formed in a shape obtained by cutting a region including the optical axis of a circular lens having an aspherical surface into a long and narrow plane. This elongated collimator lens can be formed, for example, by molding resin or optical glass. The collimator lenses 11 to 17 are closely arranged in the arrangement direction of the light emitting points so that the length direction is orthogonal to the arrangement direction of the light emitting points of the GaN-based semiconductor lasers LD1 to LD7 (left and right direction in FIG. 14).
[0059]
On the other hand, each of the GaN-based semiconductor lasers LD1 to LD7 includes an active layer having a light emission width of 2 μm, and each of the laser beams B1 in a state parallel to the active layer and a divergence angle in a direction perpendicular to each other, for example, 10 ° and 30 °. A laser emitting ~ B7 is used. These GaN-based semiconductor lasers LD1 to LD7 are arranged so that the light emitting points are arranged in a line in a direction parallel to the active layer.
[0060]
Accordingly, in the laser beams B1 to B7 emitted from the respective light emitting points, the direction in which the divergence angle is large coincides with the length direction and the divergence angle is small with respect to the elongated collimator lenses 11 to 17 as described above. Incident light is incident in a state where the direction coincides with the width direction (direction perpendicular to the length direction). That is, the collimator lenses 11 to 17 have a width of 1.1 mm and a length of 4.6 mm, and the horizontal and vertical beam diameters of the laser beams B1 to B7 incident thereon are 0.9 mm and 2. 6 mm. Each of the collimator lenses 11 to 17 has a focal length f. ₁ = 3 mm, NA = 0.6, and lens arrangement pitch = 1.25 mm.
[0061]
The condensing lens 20 is formed by cutting a region including the optical axis of a circular lens having an aspheric surface into a long and narrow shape in parallel planes, and is long in the arrangement direction of the collimator lenses 11 to 17, that is, in a horizontal direction and short in a direction perpendicular thereto. Is formed. The condenser lens 20 has a focal length f. ₂ = 23 mm, NA = 0.2. This condensing lens 20 is also formed by molding resin or optical glass, for example.
[0062]
[Operation of exposure apparatus]
Next, the operation of the exposure apparatus will be described.
[0063]
In each exposure head 166 of the scanner 162, laser beams B1, B2, B3, B4, B5, and B6 emitted in a divergent light state from each of the GaN-based semiconductor lasers LD1 to LD7 constituting the combined laser light source of the fiber array light source 66. , And B7 are collimated by corresponding collimator lenses 11-17. The collimated laser beams B <b> 1 to B <b> 7 are collected by the condenser lens 20 and converge on the incident end face of the core 30 a of the multimode optical fiber 30.
[0064]
In this example, the collimator lenses 11 to 17 and the condenser lens 20 constitute a condensing optical system, and the condensing optical system and the multimode optical fiber 30 constitute a multiplexing optical system. That is, the laser beams B1 to B7 condensed as described above by the condenser lens 20 enter the core 30a of the multimode optical fiber 30 and propagate through the optical fiber to be combined with one laser beam B. The light is emitted from the optical fiber 31 coupled to the output end of the multimode optical fiber 30.
[0065]
In each laser module, when the coupling efficiency of the laser beams B1 to B7 to the multimode optical fiber 30 is 0.85 and each output of the GaN-based semiconductor lasers LD1 to LD7 is 30 mW, the light arranged in an array For each of the fibers 31, a combined laser beam B with an output of 180 mW (= 30 mW × 0.85 × 7) can be obtained. Therefore, the output from the laser emitting unit 68 in which the six optical fibers 31 are arranged in an array is about 1 W (= 180 mW × 6).
[0066]
In the laser emitting portion 68 of the fiber array light source 66, light emission points with high luminance are arranged in a line along the main scanning direction as described above. A conventional fiber light source that couples laser light from a single semiconductor laser to a single optical fiber has low output, so a desired output could not be obtained unless multiple rows are arranged. Since the combined laser light source to be used has a high output, a desired output can be obtained even with a small number of columns, for example, one column.
[0067]
For example, in a conventional fiber light source in which a semiconductor laser and an optical fiber are coupled on a one-to-one basis, a laser having an output of about 30 mW (milliwatt) is usually used as the semiconductor laser, and the core diameter is 50 μm and the cladding diameter is 125 μm. Since a multimode optical fiber having a numerical aperture (NA) of 0.2 is used, if an output of about 1 W (watt) is to be obtained, 48 multimode optical fibers (8 × 6) must be bundled. The area of the light emitting region is 0.62 mm ² (0.675 mm × 0.925 mm), the luminance at the laser emission unit 68 is 1.6 × 10 6. ⁶ (W / m ² ) The brightness per optical fiber is 3.2 × 10 ⁶ (W / m ² ).
[0068]
On the other hand, in this example, as described above, an output of about 1 W can be obtained with the six multimode optical fibers, and the area of the light emitting region at the laser emitting portion 68 is 0.0081 mm. ² (0.325 mm × 0.025 mm), the luminance at the laser emission unit 68 is 123 × 10. ⁶ (W / m ² Thus, the brightness can be increased by about 80 times compared to the conventional case. In addition, the luminance per optical fiber is 90 × 10 ⁶ (W / m ² The brightness can be increased by about 28 times compared to the conventional case.
[0069]
Here, with reference to FIGS. 15A and 15B, the difference in depth of focus between the conventional exposure head and the exposure head of this example will be described. The diameter of the light emission region of the bundled fiber light source of the conventional exposure head in the sub-scanning direction is 0.675 mm, and the diameter of the light emission region of the fiber array light source of the exposure head of this example is 0.025 mm. As shown in FIG. 15A, in the conventional exposure head, since the light emitting area of the light source (bundle-shaped fiber light source) 1 is large, the angle of the light beam incident on the DMD 3 increases, and as a result, the light enters the scanning surface 5. The angle of the light beam increases. For this reason, the beam diameter tends to increase with respect to the light condensing direction (shift in the focus direction).
[0070]
On the other hand, as shown in FIG. 15B, in the exposure head of this example, since the diameter of the light emitting region of the fiber array light source 66 is small in the sub-scanning direction, the angle of the light beam that passes through the lens system 67 and enters the DMD 50 As a result, the angle of the light beam incident on the scanning surface 56 is reduced. That is, the depth of focus becomes deep. In this example, the diameter of the light emitting region in the sub-scanning direction is about 1/30 of the conventional one, and a depth of focus corresponding to a diffraction limit can be obtained. Therefore, it is suitable for exposure of a minute spot. This effect on the depth of focus is more prominent and effective as the required light quantity of the exposure head is larger. In this example, the size of one pixel projected on the exposure surface is 10 μm × 10 μm. The DMD is a reflective spatial light modulator, but FIGS. 15A and 15B are developed views for explaining the optical relationship.
[0071]
Image data corresponding to the exposure pattern is input to a controller (not shown) connected to the DMD 50 and temporarily stored in a frame memory in the controller. This image data is data representing the density of each pixel constituting the image by binary values (whether or not dots are recorded).
[0072]
The stage 152 that has adsorbed the photosensitive material 150 to the surface is moved at a constant speed from the upstream side to the downstream side of the gate 160 along the guide 158 by a driving device (not shown). When the leading edge of the photosensitive material 150 is detected by the detection sensor 164 attached to the gate 160 when the stage 152 passes under the gate 160, the image data stored in the frame memory is sequentially read out for a plurality of lines. A control signal is generated for each exposure head 166 based on the image data read by the data processing unit. Then, each of the micromirrors of the DMD 50 is controlled on and off for each exposure head 166 based on the generated control signal by the mirror drive control unit.
[0073]
When the DMD 50 is irradiated with laser light from the fiber array light source 66, the laser light reflected when the micromirror of the DMD 50 is in the on state forms an image on the exposed surface 56 of the photosensitive material 150 by the lens systems 54 and 58. Is done. In this manner, the laser light emitted from the fiber array light source 66 is turned on and off for each pixel, and the photosensitive material 150 is exposed in pixel units (exposure area 168) that is approximately the same number as the number of pixels used in the DMD 50. Further, when the photosensitive material 150 is moved at a constant speed together with the stage 152, the photosensitive material 150 is sub-scanned in the direction opposite to the stage moving direction by the scanner 162, and a strip-shaped exposed region 170 is formed for each exposure head 166. It is formed.
[0074]
As shown in FIGS. 16A and 16B, in the DMD 50, 600 sets of micromirror arrays in which 800 micromirrors are arranged in the main scanning direction are arranged in the subscanning direction. In this example, Control is performed so that only a part of micromirror rows (for example, 800 × 100 rows) are driven by the controller.
[0075]
As shown in FIG. 16A, a micromirror array arranged at the center of the DMD 50 may be used, and as shown in FIG. 16B, the micromirror array arranged at the end of the DMD 50 is used. May be used. In addition, when a defect occurs in some of the micromirrors, the micromirror array to be used may be appropriately changed depending on the situation, such as using a micromirror array in which no defect has occurred.
[0076]
Since the data processing speed of the DMD 50 is limited and the modulation speed per line is determined in proportion to the number of pixels used, the modulation speed per line can be increased by using only a part of the micromirror rows. Get faster. On the other hand, in the case of an exposure method in which the exposure head is continuously moved relative to the exposure surface, it is not necessary to use all the pixels in the sub-scanning direction.
[0077]
For example, when only 300 sets are used in 600 micromirror rows, modulation can be performed twice as fast per line as compared to the case of using all 600 sets. Further, when only 200 sets of 600 micromirror arrays are used, modulation can be performed three times faster per line than when all 600 sets are used. That is, an area of 500 mm in the sub-scanning direction can be exposed in 17 seconds. Further, when only 100 sets are used, modulation can be performed 6 times faster per line. That is, an area of 500 mm in the sub-scanning direction can be exposed in 9 seconds.
[0078]
The number of micromirror rows to be used, that is, the number of micromirrors arranged in the sub-scanning direction is preferably 10 or more and 200 or less, and more preferably 10 or more and 100 or less. Since the area per micromirror corresponding to one pixel is 15 μm × 15 μm, when converted to the use area of DMD50, an area of 12 mm × 150 μm or more and 12 mm × 3 mm or less is preferable, and 12 mm × 150 μm or more and 12 mm A region of × 1.5 mm or less is more preferable.
[0079]
If the number of micromirror rows to be used is within the above range, as shown in FIGS. 17A and 17B, the laser light emitted from the fiber array light source 66 is made into substantially parallel light by the lens system 67, and the DMD 50 Can be irradiated. It is preferable that the irradiation area where the laser beam is irradiated by the DMD 50 coincides with the use area of the DMD 50. When the irradiation area is wider than the use area, the utilization efficiency of the laser light is lowered.
[0080]
On the other hand, the diameter of the light beam condensed on the DMD 50 in the sub-scanning direction needs to be reduced according to the number of micromirrors arranged in the sub-scanning direction by the lens system 67, but the number of micromirror rows to be used. Is less than 10, it is not preferable because the angle of the light beam incident on the DMD 50 increases and the depth of focus of the light beam on the scanning surface 56 becomes shallow. Further, the number of micromirror rows to be used is preferably 200 or less from the viewpoint of modulation speed. The DMD is a reflective spatial light modulator, but FIGS. 17A and 17B are developed views for explaining the optical relationship.
[0081]
When the sub scanning of the photosensitive material 150 by the scanner 162 is completed and the rear end of the photosensitive material 150 is detected by the detection sensor 164, the stage 152 is moved along the guide 158 by the driving device (not shown) on the most upstream side of the gate 160. Returned to the origin at the point, and again moved along the guide 158 from the upstream side to the downstream side of the gate 160 at a constant speed.
[0082]
As described above, the exposure apparatus of this example includes a DMD in which 800 micromirror arrays in which 800 micromirrors are arranged in the main scanning direction are arranged in 600 sets in the subscanning direction. Since the control is performed so that only the micromirror array is driven, the modulation rate per line becomes faster than when all the micromirror arrays are driven. This enables high-speed exposure.
[0083]
Further, since a high-intensity fiber array light source in which output ends of optical fibers of a combined laser light source are arranged in an array is used as a light source for illuminating the DMD, an exposure apparatus having a high output and a deep focal depth Can be realized. Furthermore, since the output of each fiber light source is increased, the number of fiber light sources necessary to obtain a desired output is reduced, and the cost of the exposure apparatus can be reduced.
[0084]
In particular, in this example, since the cladding diameter of the output end of the optical fiber is made smaller than the cladding diameter of the incident end, the diameter of the light emitting portion is further reduced, and the brightness of the fiber array light source can be increased. Thereby, an exposure apparatus having a deeper depth of focus can be realized. For example, even in the case of ultra-high resolution exposure with a beam diameter of 1 μm or less and a resolution of 0.1 μm or less, a deep depth of focus can be obtained, and high-speed and high-definition exposure is possible. Therefore, it is suitable for a thin film transistor (TFT) exposure process that requires high resolution.
[0085]
Next, a modification of the exposure apparatus described above will be described.
[0086]
[Applications of exposure equipment]
The above-described exposure apparatus is, for example, a dry film resist (DFR) exposure process in a printed wiring board (PWB) manufacturing process, and a color filter in a liquid crystal display (LCD) manufacturing process. It can be suitably used for applications such as formation, DFR exposure in a TFT manufacturing process, and DFR exposure in a plasma display panel (PDP) manufacturing process.
[0087]
Furthermore, the above exposure apparatus can be used for various laser processing such as laser ablation, sintering, and lithography in which a part of the material is removed by evaporation, scattering, etc. by laser irradiation. The above exposure apparatus has a high output and can be exposed at a high speed and a long focal depth, so that it can be used for fine processing such as laser ablation. For example, instead of performing development processing, the resist is removed according to a pattern by ablation to create a PWB, or the above exposure apparatus can be used to form a PWB pattern by ablation directly without using a resist. it can. It can also be used to form microchannels with a groove width of several tens of μm in a lab-on-chip in which many solutions are mixed, reacted, separated, detected, etc. on glass or plastic chips.
[0088]
In particular, the exposure apparatus described above uses a GaN-based semiconductor laser as a fiber array light source, and therefore can be suitably used for the laser processing described above. That is, the GaN-based semiconductor laser can be driven with a short pulse, and sufficient power can be obtained for laser ablation and the like. In addition, since it is a semiconductor laser, it can be driven at a high repetition rate of about 10 MHz unlike a solid-state laser having a low driving speed, and high-speed exposure is possible. Furthermore, since metal has a large light absorption rate of laser light having a wavelength of around 400 nm and can be easily converted into thermal energy, laser ablation and the like can be performed at high speed.
[0089]
When exposing a liquid resist used for patterning a TFT and a liquid resist used for patterning a color filter, in order to eliminate sensitivity reduction (desensitization) due to oxygen inhibition, the exposure is performed in a nitrogen atmosphere. It is preferable to expose the exposure material. Exposure in a nitrogen atmosphere suppresses oxygen inhibition of the photopolymerization reaction, increases the sensitivity of the resist, and enables high-speed exposure.
[0090]
In the exposure apparatus, either a photon mode photosensitive material in which information is directly recorded by exposure or a heat mode photosensitive material in which information is recorded by heat generated by exposure can be used. When using a photon mode photosensitive material, a GaN-based semiconductor laser, a wavelength conversion solid-state laser, or the like is used for the laser device. When using a heat mode photosensitive material, an AlGaAs-based semiconductor laser (infrared laser), A solid state laser is used.
[0091]
[Other spatial light modulators]
In the above example, the DMD micromirror is partially driven. However, the length of the direction corresponding to the predetermined direction is longer than the length of the direction intersecting the predetermined direction. Accordingly, even if a long and narrow DMD in which a number of micromirrors whose reflection surface angles can be changed is two-dimensionally arranged is used, the number of micromirrors for controlling the reflection surface angle is reduced. Can be fast.
[0092]
In the above example, an exposure head provided with a DMD as a spatial light modulator has been described. For example, a micro electro mechanical systems (SMEM) type spatial light modulator (SLM) or an electro-optic effect allows transmission. Even when a spatial light modulation element other than the MEMS type, such as an optical element (PLZT element) that modulates light or a liquid crystal optical shutter (FLC), is used, some of the pixel parts are arranged with respect to all the pixel parts arranged on the substrate. By using, it is possible to increase the modulation speed per pixel and per main scanning line, so the same effect can be obtained.
[0093]
Note that MEMS is a general term for a micro system that integrates micro-sized sensors, actuators, and control circuits based on a micro-machining technology based on an IC manufacturing process, and a MEMS type spatial light modulator is an electrostatic force. It means a spatial light modulation element driven by an electromechanical operation using
[0094]
[Other exposure methods]
As shown in FIG. 18, similarly to the above example, the entire surface of the photosensitive material 150 may be exposed by a single scan in the X direction by the scanner 162, as shown in FIGS. 19A and 19B. Then, after scanning the photosensitive material 150 in the X direction by the scanner 162, the scanner 162 is moved one step in the Y direction and scanned in the X direction. The entire surface 150 may be exposed. In this example, the scanner 162 includes 18 exposure heads 166.
[0095]
[Other laser devices (light sources)]
In the above example, an example using a fiber array light source including a plurality of combined laser light sources has been described. However, the laser device is not limited to a fiber array light source in which combined laser light sources are arrayed. For example, a fiber array light source obtained by arraying fiber light sources including one optical fiber that emits laser light incident from a single semiconductor laser having one light emitting point can be used.
[0096]
As a light source having a plurality of light emitting points, for example, as shown in FIG. 20, a laser array in which a plurality of (for example, seven) chip-shaped semiconductor lasers LD1 to LD7 are arranged on a heat block 100 is used. Can be used. Further, a chip-shaped multicavity laser 110 in which a plurality of (for example, five) light emitting points 110a shown in FIG. 21A is arranged in a predetermined direction is known. Since the multicavity laser 110 can arrange the light emitting points with higher positional accuracy than the case where the chip-shaped semiconductor lasers are arranged, it is easy to multiplex laser beams emitted from the respective light emitting points. However, as the number of light emitting points increases, the multicavity laser 110 is likely to be bent at the time of laser manufacturing. Therefore, the number of light emitting points 110a is preferably 5 or less.
[0097]
In the exposure head of the present invention, the multi-cavity laser 110 and a plurality of multi-cavity lasers 110 on the heat block 100 as shown in FIG. 21B are in the same direction as the arrangement direction of the light emitting points 110a of each chip. A multi-cavity laser array arranged in the above can be used as a laser device (light source).
[0098]
The combined laser light source is not limited to one that combines laser beams emitted from a plurality of chip-shaped semiconductor lasers. For example, as shown in FIG. 22, a combined laser light source including a chip-shaped multicavity laser 110 having a plurality of (for example, three) light emitting points 110a can be used. This combined laser light source is configured to include a multi-cavity laser 110, one multi-mode optical fiber 130, and a condensing lens 120. The multi-cavity laser 110 can be composed of, for example, a GaN-based laser diode having an oscillation wavelength of 405 nm.
[0099]
In the above configuration, each of the laser beams B emitted from each of the plurality of light emitting points 110 a of the multicavity laser 110 is collected by the condenser lens 120 and enters the core 130 a of the multimode optical fiber 130. The laser light incident on the core 130a propagates in the optical fiber, is combined into one, and is emitted.
[0100]
A plurality of light emitting points 110 a of the multi-cavity laser 110 are juxtaposed within a width substantially equal to the core diameter of the multi-mode optical fiber 130, and a focal point substantially equal to the core diameter of the multi-mode optical fiber 130 is used as the condenser lens 120. By using a convex lens of a distance or a rod lens that collimates the outgoing beam from the multicavity laser 110 only in a plane perpendicular to the active layer, the coupling efficiency of the laser beam B to the multimode optical fiber 130 can be increased. it can.
[0101]
23, a multi-cavity laser 110 having a plurality of (for example, three) emission points is used, and a plurality of (for example, nine) multi-cavity lasers 110 are equally spaced from each other on the heat block 111. A combined laser light source including the laser array 140 arranged in (1) can be used. The plurality of multi-cavity lasers 110 are arranged and fixed in the same direction as the arrangement direction of the light emitting points 110a of each chip.
[0102]
This combined laser light source includes a laser array 140, a plurality of lens arrays 114 arranged corresponding to each multi-capability laser 110, and a single lens arranged between the laser array 140 and the plurality of lens arrays 114. A rod lens 113, one multimode optical fiber 130, and a condenser lens 120 are provided. The lens array 114 includes a plurality of microlenses corresponding to the emission points of the multi-capability laser 110.
[0103]
In the above configuration, each of the laser beams B emitted from each of the plurality of light emitting points 10a of the plurality of multi-cavity lasers 110 is condensed in a predetermined direction by the rod lens 113 and then each microlens of the lens array 114. Is collimated. The collimated laser beam L is condensed by the condenser lens 120 and enters the core 130a of the multimode optical fiber 130. The laser light incident on the core 130a propagates in the optical fiber, is combined into one, and is emitted.
[0104]
Still another example of the combined laser light source will be described. In this combined laser light source, as shown in FIGS. 24A and 24B, a heat block 182 having an L-shaped cross section in the optical axis direction is mounted on a substantially rectangular heat block 180, and two heats are provided. A storage space is formed between the blocks. On the upper surface of the L-shaped heat block 182, a plurality of (for example, two) multi-cavity lasers 110 in which a plurality of light emitting points (for example, five) are arranged in an array form the light emitting points 110a of each chip. It is arranged and fixed at equal intervals in the same direction as the arrangement direction.
[0105]
A concave portion is formed in the substantially rectangular heat block 180, and a plurality of (for example, two) light emitting points (for example, five) are arranged in an array on the upper surface of the space side of the heat block 180. The multi-cavity laser 110 is arranged such that its emission point is located on the same vertical plane as the emission point of the laser chip arranged on the upper surface of the heat block 182.
[0106]
On the laser beam emission side of the multi-cavity laser 110, a collimator lens array 184 in which collimator lenses are arranged corresponding to the light emission points 110a of the respective chips is arranged. In the collimating lens array 184, the length direction of each collimating lens coincides with the direction in which the divergence angle of the laser beam is large (the fast axis direction), and the width direction of each collimating lens is in the direction in which the divergence angle is small (slow axis direction). They are arranged to match. Thus, by collimating and integrating the collimating lenses, the space utilization efficiency of the laser light can be improved, the output of the combined laser light source can be increased, and the number of parts can be reduced and the cost can be reduced. .
[0107]
Further, on the laser beam emitting side of the collimating lens array 184, there is one multimode optical fiber 130, and a condensing lens 120 that condenses and combines the laser beam at the incident end of the multimode optical fiber 130. Has been placed.
[0108]
In the above configuration, each of the laser beams B emitted from each of the plurality of light emitting points 10a of the plurality of multi-cavity lasers 110 arranged on the laser blocks 180 and 182 is collimated by the collimating lens array 184, The light is condensed by the condensing lens 120 and enters the core 130 a of the multimode optical fiber 130. The laser light incident on the core 130a propagates in the optical fiber, is combined into one, and is emitted.
[0109]
As described above, this combined laser light source can achieve particularly high output by the multi-stage arrangement of multi-cavity lasers and the array of collimating lenses. By using this combined laser light source, a higher-intensity fiber array light source or bundle fiber light source can be formed, which is particularly suitable as a fiber light source constituting the laser light source of the exposure apparatus of the present invention.
[0110]
It should be noted that a laser module in which each of the above combined laser light sources is housed in a casing and the emission end portion of the multimode optical fiber 130 is pulled out from the casing can be configured.
[0111]
In the above example, another optical fiber having the same core diameter as the multimode optical fiber and a smaller cladding diameter than the multimode optical fiber is coupled to the output end of the multimode optical fiber of the combined laser light source. Although an example of increasing the brightness of the array light source has been described, for example, a multimode optical fiber having a cladding diameter of 125 μm, 80 μm, 60 μm, or the like may be used without coupling another optical fiber to the emission end.
[0112]
[Light distribution correction optical system]
In the above example, the light amount distribution correcting optical system including a pair of combination lenses is used for the exposure head. This light quantity distribution correcting optical system changes the light beam width at each emission position so that the ratio of the light beam width at the peripheral part to the light beam width at the central part near the optical axis is smaller on the output side than on the incident side. When the parallel light beam from the light source is irradiated onto the DMD, the light amount distribution on the irradiated surface is corrected so as to be substantially uniform. Hereinafter, the operation of this light quantity distribution correcting optical system will be described.
[0113]
First, as shown in FIG. 25A, the case where the entire luminous flux widths (total luminous flux widths) H0 and H1 are the same for the incident luminous flux and the outgoing luminous flux will be described. In FIG. 25A, the portions denoted by reference numerals 51 and 52 virtually indicate the entrance surface and the exit surface in the light quantity distribution correction optical system.
[0114]
In the light quantity distribution correcting optical system, it is assumed that the light flux widths h0 and h1 of the light beam incident on the central part near the optical axis Z1 and the light beam incident on the peripheral part are the same (h0 = hl). The light quantity distribution correcting optical system expands the light beam width h0 of the incident light beam in the central portion with respect to the light having the same light beam width h0 and h1 on the incident side, and conversely with respect to the incident light beam in the peripheral portion. Thus, the light beam width h1 is reduced. That is, the width h10 of the outgoing light beam at the center and the width h11 of the outgoing light beam at the periphery are set to satisfy h11 <h10. In terms of the ratio of the luminous flux width, the ratio “h11 / h10” of the luminous flux width in the peripheral portion to the luminous flux width in the central portion on the emission side is smaller than the ratio (h1 / h0 = 1) on the incident side ( (H11 / h10) <1).
[0115]
By changing the light flux width in this way, the light flux in the central part, which normally has a large light quantity distribution, can be utilized in the peripheral part where the light quantity is insufficient, and the overall light utilization efficiency is not reduced. In addition, the light quantity distribution on the irradiated surface is made substantially uniform. The degree of uniformity is, for example, such that the unevenness in the amount of light in the effective area is within 30%, preferably within 20%.
[0116]
The actions and effects of such a light quantity distribution correcting optical system are the same when the entire light flux width is changed between the incident side and the exit side (FIGS. 25B and 25C).
[0117]
FIG. 25B shows a case where the entire light flux width H0 on the incident side is “reduced” to the width H2 and emitted (H0> H2). Even in such a case, the light quantity distribution correcting optical system uses the light flux widths h0 and h1 that are the same on the incident side, and the light flux width h10 in the central portion is larger than that in the peripheral portion on the outgoing side. In addition, the light flux width h11 in the peripheral portion is made smaller than that in the central portion. Considering the reduction rate of the light beam, the reduction rate with respect to the incident light beam in the central part is made smaller than that in the peripheral part, and the reduction rate with respect to the incident light beam in the peripheral part is made larger than that in the central part. Also in this case, the ratio “H11 / H10” of the light flux width in the peripheral portion to the light flux width in the central portion is smaller than the ratio (h1 / h0 = 1) on the incident side ((h11 / h10) <1). .
[0118]
FIG. 25C shows a case where the entire light flux width H0 on the incident side is “enlarged” by the width Η3 and emitted (H0 <H3). Even in such a case, the light quantity distribution correcting optical system uses the light flux widths h0 and h1 that are the same on the incident side, and the light flux width h10 in the central portion is larger than that in the peripheral portion on the outgoing side. In addition, the light flux width h11 in the peripheral portion is made smaller than that in the central portion. Considering the expansion rate of the light beam, the expansion rate for the incident light beam in the central portion is made larger than that in the peripheral portion, and the expansion rate for the incident light beam in the peripheral portion is made smaller than that in the central portion. Also in this case, the ratio “h11 / h10” of the light flux width in the peripheral portion to the light flux width in the central portion is smaller than the ratio (h1 / h0 = 1) on the incident side ((h11 / h10) <1). .
[0119]
As described above, the light amount distribution correcting optical system changes the light beam width at each emission position, and the ratio of the light beam width in the peripheral part to the light beam width in the central part near the optical axis Z1 is larger on the outgoing side than on the incident side. Since the light has the same light flux width on the incident side, the light flux width in the central portion is larger than that in the peripheral portion, and the light flux width in the peripheral portion is larger than that in the central portion. Get smaller. As a result, it is possible to make use of the light beam at the center part to the peripheral part, and it is possible to form a light beam cross-section with a substantially uniform light amount distribution without reducing the light use efficiency of the entire optical system.
[0120]
FIG. 27 shows a light amount distribution of illumination light obtained by the light amount distribution correcting optical system. The horizontal axis indicates coordinates from the optical axis, and the vertical axis indicates the light amount ratio (%). For comparison, FIG. 26 shows a light amount distribution (Gaussian distribution) of illumination light when correction is not performed. As can be seen from FIG. 26 and FIG. 27, a light amount distribution that is substantially uniform is obtained by performing correction using the light amount distribution correcting optical system as compared with the case where correction is not performed. Thereby, it is possible to carry out exposure with uniform laser light without reducing the use efficiency of light in the exposure head.
[0121]
[Other imaging optics]
In the above example, two sets of lenses are arranged as the imaging optical system on the light reflection side of the DMD used for the exposure head. However, an imaging optical system for enlarging the laser beam to form an image may be arranged. . By expanding the cross-sectional area of the light beam reflected by the DMD, the exposure area area (image area) on the exposed surface can be expanded to a desired size.
[0122]
For example, as shown in FIG. 28A, the exposure head is configured to illuminate the DMD 50, the illumination device 144 for irradiating the DMD 50 with laser light, the lens systems 454, 458, the DMD 50 for enlarging the laser light reflected by the DMD 50, and forming an image. A microlens array 472 in which a large number of microlenses 474 are arranged corresponding to each of the pixels, an aperture array 476 in which a large number of apertures 478 are provided corresponding to each microlens of the microlens array 472, and a laser that has passed through the aperture It can be configured by lens systems 480 and 482 that form an image of light on the exposed surface 56.
[0123]
In this exposure head, when laser light is irradiated from the illumination device 144, the cross-sectional area of the light beam reflected by the DMD 50 in the ON direction is enlarged several times (for example, twice) by the lens systems 454 and 458. . The expanded laser light is condensed corresponding to each pixel of the DMD 50 by each microlens of the microlens array 472, and passes through the corresponding aperture of the aperture array 476. The laser light that has passed through the aperture is imaged on the exposed surface 56 by the lens systems 480 and 482.
[0124]
In this imaging optical system, the laser light reflected by the DMD 50 is magnified several times by the magnifying lenses 454 and 458 and projected onto the exposed surface 56, so that the entire image area is widened. At this time, if the microlens array 472 and the aperture array 476 are not arranged, as shown in FIG. 28B, one pixel size (spot size) of each beam spot BS projected onto the exposed surface 56 is exposed. It becomes larger according to the size of the area 468, and the MTF (Modulation Transfer Function) characteristic representing the sharpness of the exposure area 468 is deteriorated.
[0125]
On the other hand, when the microlens array 472 and the aperture array 476 are arranged, the laser light reflected by the DMD 50 is condensed corresponding to each pixel of the DMD 50 by each microlens of the microlens array 472. Thereby, as shown in FIG. 28C, even when the exposure area is enlarged, the spot size of each beam spot BS can be reduced to a desired size (for example, 10 μm × 10 μm), and the MTF characteristics are obtained. It is possible to perform high-definition exposure while preventing a decrease in the image quality. The exposure area 468 is tilted because the DMD 50 is tilted and arranged in order to eliminate a gap between pixels.
[0126]
In addition, even if the beam is thick due to the aberration of the microlens, the beam can be shaped by the aperture so that the spot size on the exposed surface 56 becomes a constant size, and corresponding to each pixel. By passing the provided aperture, it is possible to prevent crosstalk between adjacent pixels.
[0127]
Further, by using a high-intensity light source in the illumination device 144 as in the above example, the angle of the light beam incident on each microlens of the microlens array 472 from the lens 458 is reduced, so that one of the light beams of adjacent pixels can be obtained. It is possible to prevent the part from entering. That is, a high extinction ratio can be realized.
[Brief description of the drawings]
FIG. 1 is a perspective view showing the appearance of an exposure apparatus using optical fibers connected by the method of the present invention.
2 is a perspective view showing a configuration of a scanner of the exposure apparatus in FIG. 1. FIG.
3A is a plan view showing an exposed region formed on a photosensitive material, and FIG. 3B is a diagram showing an array of exposure areas by each exposure head.
4 is a perspective view showing a schematic configuration of an exposure head of the exposure apparatus in FIG. 1. FIG.
5A is a sectional view in the sub-scanning direction along the optical axis showing the configuration of the exposure head shown in FIG. 4, and FIG. 5B is a side view of FIG.
FIG. 6 is a partially enlarged view showing a configuration of a digital micromirror device (DMD).
7A and 7B are explanatory diagrams for explaining the operation of the DMD.
FIGS. 8A and 8B are plan views showing the arrangement of exposure beams and scanning lines in a case where the DMD is not inclined and in a case where the DMD is inclined. FIG.
9A is a perspective view showing the configuration of a fiber array light source, FIG. 9B is a partially enlarged view of FIG. 9A, and FIGS. 9C and 9D are plan views showing the arrangement of light emitting points in a laser emitting section.
FIG. 10 is a diagram showing the configuration of a multimode optical fiber
FIG. 11 is a plan view showing the configuration of a combined laser light source.
FIG. 12 is a plan view showing the configuration of a laser module.
13 is a side view showing the configuration of the laser module shown in FIG.
14 is a partial side view showing the configuration of the laser module shown in FIG. 12;
15A and 15B are cross-sectional views along the optical axis showing the difference between the depth of focus in the conventional exposure apparatus and the depth of focus in the exposure apparatus of FIG.
FIGS. 16A and 16B are diagrams showing examples of DMD usage areas; FIGS.
FIGS. 17A and 17B are side views when the DMD use area is appropriate, and FIG. 17B is a sectional view in the sub-scanning direction along the optical axis of FIG.
FIG. 18 is a plan view for explaining an exposure method for exposing a photosensitive material by one scanning by a scanner.
FIGS. 19A and 19B are plan views for explaining an exposure method for exposing a photosensitive material by a plurality of scans performed by a scanner. FIGS.
FIG. 20 is a perspective view showing the configuration of a laser array.
21A is a perspective view showing a configuration of a multi-cavity laser, and FIG. 21B is a perspective view of a multi-cavity laser array in which the multi-cavity lasers shown in FIG.
FIG. 22 is a plan view showing another configuration of the combined laser light source.
FIG. 23 is a plan view showing another configuration of the combined laser light source.
24A is a plan view showing another configuration of the combined laser light source, and FIG. 24B is a sectional view taken along the optical axis of FIG.
FIG. 25 is an explanatory diagram about the concept of correction by the light amount distribution correction optical system.
FIG. 26 is a graph showing the light amount distribution when the light source has a Gaussian distribution and the light amount distribution is not corrected.
FIG. 27 is a graph showing the light amount distribution after correction by the light amount distribution correcting optical system;
28A is a cross-sectional view along the optical axis showing the configuration of another exposure head having a different coupling optical system, and FIG. 28B is light projected onto the exposure surface when a microlens array or the like is not used. The top view which shows an image, (C) is a top view which shows the optical image projected on a to-be-exposed surface when a micro lens array etc. are used
FIG. 29 is a diagram for explaining an optical fiber connection method according to an embodiment of the present invention;
FIG. 30 is a diagram for explaining an optical fiber connection method according to another embodiment of the present invention;
FIG. 31 is a diagram for explaining an optical fiber connection method according to still another embodiment of the present invention;
[Explanation of symbols]
LD1-LD7 GaN semiconductor laser
30, 31 Multimode optical fiber
30a, 31a Multimode optical fiber core
30b, 31b Multimode optical fiber cladding
30c, 30c 'Small diameter portion of multimode optical fiber
32 Multimode optical fiber with intermediate outer diameter
50 Digital Micromirror Device (DMD)
64 laser module
66 Fiber array light source
68 Laser emitting part
150 Photosensitive material
152 stages
162 Scanner
166 Exposure head
168 Exposure area
170 Exposed area

Claims (2)

A method of connecting two optical fibers having different clad diameters,
The clad at one end of the optical fiber having a large clad diameter is processed so that the diameter of its end face is an intermediate diameter between the clads of both optical fibers,
An optical fiber connecting method, comprising: fusing an optical fiber having a small cladding diameter to one end of the processed optical fiber. A method of connecting two optical fibers having different clad diameters,
An optical fiber having a large cladding diameter and an optical fiber having a small cladding diameter are fused to one end and the other end of an optical fiber having an intermediate cladding diameter of these optical fibers, respectively. Optical fiber connection method.

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