JP2005268512A - Ld drive circuit and exposure system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LD drive unit in which even when a plurality of LDs are used at the same time in an exposure system, an electric insulation between cases of the LD can be made unwanted, and also the heatsink of the drive element of the LD has no need to be used. <P>SOLUTION: The LD drive unit comprises the plurality of LDs and a drive circuit driving the LD under current fixed control by the drive element. Either an anode or a cathode of the LD is connected to the case of such LD, and the case is connected to either an LD driving power source or a GND. One of terminals of the drive element is the heatsink, which is connected to the LD driving power source or another of the GND, and all the plurality of LDs have the same circuit structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus that exposes a recording material using a laser diode (LD) as a light source and an LD drive unit used therefor, and more particularly, to an exposure apparatus that uses a high-power LD that requires a cooling mechanism as a light source and the exposure apparatus. The present invention relates to an LD drive unit.

  In an exposure apparatus that uses a plurality of relatively high output LDs, such as a thermal type CTP, in order to dissipate the heat generated from the LD to the mounting substrate via the LD case, the case and the anode or cathode of the LD One or the other is often connected. In many cases, a plurality of driving power supplies are used simultaneously. In such a case, each LD may be at a different potential, and it is necessary to electrically insulate the LD cases from each other in advance. However, if the LD cases are insulated from each other, the thermal conductivity generally decreases. For this reason, the amount of heat released from the case to the mounting substrate is reduced, which affects the life and performance of the LD.

In addition, a relatively large current is required to flow through the high output LD. Therefore, when driving a high-power LD with a constant current, for example, a driving element for amplification such as a transistor is used, and a heat sink is provided via a heat dissipation plate connected to either the collector or emitter of this driving element. It is usually done. Thereby, the heat generated from the drive element is dissipated. However, the power supply board on which the drive element is mounted for the heat sink must be a relatively large object. An example of such an LD driving circuit is described in Patent Document 1 or 2, for example.
JP 2003-264337 A JP 2003-264338 A

  According to the present invention, even when a plurality of LDs are used at the same time in the exposure apparatus, electrical insulation between the LD cases can be eliminated, and further, it is not necessary to use a heat sink for the LD drive elements. It is an object to provide an LD driving unit.

  A first aspect of the present invention is an LD drive unit comprising a plurality of LDs and a drive circuit for driving the LDs with constant current control by drive elements, wherein either the anode or the cathode of the LD is the LD. The case is connected to either the LD driving power supply or GND, one of the terminals of the drive element is a heat sink, and the heat sink is the LD driving power supply. Alternatively, the LD driving unit is connected to the other GND and has the same circuit configuration for all of the plurality of LDs.

  Here, it is preferable that a heat sink is not connected to the heat radiating plate. Further, it is preferable that all the cases have the same potential. Further, it is preferable that all of the cases are electrically connected to each other. Further, it is preferable that the driving circuit control power source and the LD driving power source are separate and independent.

  A second aspect of the present invention is an LD driving unit comprising a plurality of LDs and a driving circuit for driving the LDs with constant current control by a driving element, wherein the driving circuit is provided at one end of a reference resistance element of the driving circuit. One of the collector and emitter of the element that is not a heat sink is connected to one feedback circuit for constant current control, and the other end of the reference resistance element is connected to the cathode of the LD or Either one of the anodes and the other feedback circuit for constant current control are connected, and the other one of the collectors or emitters, which is a heat sink, is either the LD driving power supply or GND. And the other one of the cathode or anode is connected to the other one of the LD driving power source or the GND, and A LD drive unit, characterized in that the same circuit configuration for the number of LD.

  According to a third aspect of the present invention, there is provided an exposure apparatus comprising any one of the above-described LD drive units.

  Even when a plurality of LDs are used simultaneously, electrical insulation between the LD cases can be eliminated. Thereby, since the thermal conductivity from the case to the mounting plate is also improved, the heat radiation from the case can be secured. In addition, since it is not necessary to use a heat sink for the LD drive element, the power supply board becomes smaller. Thereby, a miniaturized LD drive unit is obtained.

  Embodiments of the present invention will be described below with reference to the drawings. Here, a description will be given by taking as an example a multi-beam CTP in which a plurality of high-power LDs of several hundred mW to several W are used, and the exposure is performed by transmitting the LD to the exposure head via an optical fiber. FIG. 1 shows a schematic configuration of such an exposure apparatus 1. FIG. 1A is a schematic side view of the exposure apparatus 1, and FIG. 1B is a top view. The exposure apparatus 1 includes a rotating drum 20, a support column 22, a rotating shaft 23, a main scanning mechanism including a drum rotating mechanism (not shown), a rail 11, a moving gantry 65, a sub scanning mechanism including a moving gantry driving mechanism (not shown), a light source ( LD) 40, an exposure head 60, an optical fiber 61, and a lens 62, a cooling mechanism including an electronic cooling element 50, an air cooling fan 51, and a heat sink, and a main mount 10 on which these are mounted. In addition, a light amount measuring mechanism of the LD, a focus adjusting mechanism of the lens 62, a recording material feed mechanism, a discharge mechanism, and the like are provided, but not shown. Each part of the exposure apparatus 1 operates under the control of a control unit (not shown).

  The rotating drum 20 is a cylindrical member that is rotatably attached to the main frame 10 of the exposure apparatus 1 via a support column 22 and a rotating shaft 23. When the rotary drum 20 forms an image by light exposure, the recording material 30 is wound around and held on the outer peripheral surface thereof. Further, in accordance with a control signal output from the control unit, a drum drive mechanism (not shown) drives the motor and rotates in the direction of arrow R in FIG. Thereby, main scanning with respect to the recording material 30 is performed.

  The rail 11 is installed on the main gantry 10 in parallel with the rotation shaft 23 of the rotary drum 20. The length and position of the rail 11 are set so that a movable mount 65 described later can move over the entire width of the rotary drum 20. The movable gantry 65 is installed on the rail 11 and is attached to be movable in parallel to the direction of the rotary shaft 23 by a movable gantry driving mechanism (not shown). As the movable frame 65 moves along the rail 11, sub-scanning is performed on the recording material. This moving direction is the sub-scanning direction P.

  The light source 40 is provided on a leg 42 provided on the main frame 10, and 16 high-power LDs 40 are arranged and fixed in parallel on an aluminum LD mounting table 41. The metal case of each LD is screwed in direct contact with the mounting base 41, and can conduct electricity and conduct heat with the mounting base. That is, the metal cases of all the LDs and the LD mounting base 41 have the same potential. Further, each LD is driven by an LD driving circuit (1) to (16) 70 independent for each LD in accordance with a command from the control unit. The LD drive circuit 70 will be described later. The LD driving unit includes an LD fixed to the mounting base and an LD driving circuit 70 connected to each LD.

  An optical fiber 61 is connected to the exit port of each LD via a connector so that optical transmission is possible. The optical fiber 61 is connected to an exposure head 60 that is bundled together and fixed on a moving table 63.

  The cross section of the LD mounting base 41 is substantially L-shaped, and a Peltier element 50, which is an electronic cooling element, is provided on the back of the portion where the LD is fixed. The Peltier element 50 is further provided with an air cooling fan 51 via a heat sink, and heat generated in the LD is exhausted from the heat sink and the air cooling fan 51 from the LD mounting base 41 via the Peltier element 50.

  On the moving table 63, an exposure head 60 and a lens 62 are fixed with their optical axes aligned. The lens 62 is provided in the vicinity of the exit of the exposure head 60 from the optical fiber 61 and converges the light beam on the surface of the recording material 30. The lens 62 may be either a single lens or a lens group configured by combining a plurality of lenses. The light beam emitted from the LD of the light source 40 through the optical fiber 61 and the exit of the exposure head 60 is converged on the recording material 30 through the lens 62 to expose the recording material.

  Next, the LD drive circuit 70 will be described. The LD driving circuit 70 has the same configuration for 16 LDs, and the potentials of the 16 LD cases are the same. A schematic configuration example of one of the circuits is shown in FIG. The LD 121 is housed in a metal case 122, and the anode of the LD 121 is connected to the metal case 122 by a metal wire 123. The metal case 122 is screwed so as to be in direct contact with the mounting base 41. As a result, the anode of the LD 121 and the mounting base 41 have the same potential. Two lines through which current flows to the LD 121 are connected to the LD driving circuit 70 via the connector 120, and the other one is grounded by the ground 124.

  The LD drive circuit 70 current-drives the LD 121 according to the control signal 100 from the control unit. The control signal 100 controls the drive element 102 via the operational amplifier 101. Under this control, the drive element 102 causes a drive current to flow from the ground terminal 124 to the LD drive power supply 103 (−Vcc) via the LD 121 and the reference resistance element 110. In addition, two feedback circuits 111 and 112 to the operational amplifier 101 are provided at both ends of the reference resistance element 110, so that the current value flowing through the reference resistance element 110 becomes a constant value corresponding to the control signal. It is controlled to become.

  A schematic external view of the driving element 102 used here is shown in FIG. The drive element 102 is a normal LD driving transistor, and a heat sink 125 is fixed to the main body. In this LD drive circuit 70, the heat dissipation plate 125 and the collector 127 of the drive element 102 are connected to the LD drive power supply 103, and the heat generated in the drive element 102 is transmitted to the LD drive power supply 103 via the heat dissipation plate 125. Heat is radiated from the provided power supply board. Here, the drive element 102 is not provided with a heat sink. This is because the area of the power supply substrate is relatively large and almost the entire surface can be used instead of the heat sink.

  As described above, in the driving circuit that performs constant current control, the potential of the collector 127 of the driving element 102 is set to the power supply potential (−Vcc), and the driving element 102 does not use a heat sink. In this way, the potential of the terminal connected to the heat dissipation plate of the drive element is set to the power supply potential Vcc or the ground potential GND. For this reason, the heat generated in the drive element 102 is conducted from the radiator plate 125 to the substrate on which the power source 103 is provided, and the power source substrate can be used as a radiator plate. As a result, it is possible to eliminate the use of a heat sink that is conventionally required for heat dissipation for each drive element, and the LD drive unit can be downsized.

  Such a circuit configuration is made the same for all LDs. This is shown in FIG. FIG. 4 is a conceptual diagram of the LD drive unit. Here, the drive circuits (1) to (16) corresponding to 16 LDs all have the same circuit configuration. That is, the collectors of all the drive elements are connected to the LD drive power supply (-Vcc) of the same voltage, and the heat sink is not used for the drive elements. In addition, for all the LDs, the anodes were set to the same potential as the LD mounting base 41 (ground potential GND). As a result, there is no need to electrically insulate each LD, there is no fear of malfunction, and a sufficient amount of heat dissipation can be obtained.

  The configuration of such an LD drive circuit can take various variations on the premise that all LDs have the same circuit configuration. Various types of these variations will be described with reference to FIGS. First, FIG. 5 is similar to the drive circuit of FIG. 2, but the ground terminal 124 in FIG. 2 is the drive power supply (+ Vcc) in FIG. 6, and the drive power supply (−Vcc) in FIG. Is the grounding end 131. That is, the potential of the circuit portion through which the drive current flows is shifted upward by approximately Vcc. On the other hand, the LD has an anode connected to the LD case as in FIG. For this reason, the LD case becomes the potential (+ Vcc) of the drive power supply. Even in such a circuit configuration, insulation for each LD is not necessary, as in the configuration of FIG. Further, heat can be radiated from the power supply substrate without using the heat sink of the driving element.

  The circuit configuration in FIG. 6 is similar to that in FIG. 2 in the periphery of the operational amplifier, but the configurations regarding the LD 143 and the reference resistance element 142 are different. The drive element 141 causes a current to flow from the drive power supply (+ Vcc) to the ground terminal 146 via the reference resistance element 142 and the LD 143 by a signal from the control signal 100 via the operational amplifier. The two feedback circuits 150 and 151 provide feedback to the operational amplifier for constant current control. At this time, since the cathode of the LD 143 is connected to the metal case 145 by the metal wire 144, the metal case 145 becomes the ground potential. For this reason, it is not necessary to insulate the metal cases from each other. Further, the collector of the driving element 141 is connected to the power source, and no heat sink is used. Even in this case, the heat generated in the drive element 141 can be dissipated from the power supply substrate.

  The circuit configuration of FIG. 7 is similar to the circuit configuration of FIG. 6, but the drive power supply 140 in FIG. 6 becomes the ground terminal 161 in FIG. 7, and the ground terminal 146 in FIG. 6 is the drive power supply (−Vcc) in FIG. Is different. Since the structure of the LD portion is the same as that shown in FIG. 6, the cathode of the LD shown in FIG. Therefore, the potential of the LD case is also −Vcc. Since this is the same for all LD cases, it is not necessary to insulate a plurality of LD cases from each other in this example as well.

  The circuit configuration in FIG. 8 is similar to the circuit configuration in FIG. 2, but a power source 171 (+ Vcc) and a power source 172 (−Vcc) are provided as control power sources for the operational amplifier 170 independently of the LD drive power source 173. Different points. In this way, the heat generated in the drive element can be reduced as much as possible and the burden on the drive element is reduced, so the amount of heat generated in the drive element is reduced and the power supply board connected to the drive element is reduced. The area can be reduced. Furthermore, it goes without saying that the same effects as those described above can also be obtained.

  In addition, the aspect of this invention is not limited to said specific example. The exposure apparatus is not limited to CTP, and can be applied without particular limitation as long as the recording material is exposed using an LD or LED. Further, the present invention may be applied to an exposure apparatus that uses a relatively low output LD or the like, so that an insulation process or a heat sink is not necessary. In the above description, the heat dissipation plate of the driving element is described as being connected to the same potential as the collector. However, when the emitter is connected to the same potential as the heat dissipation plate, the heatsink is The heat dissipation plate can be configured to dissipate heat to the power supply substrate without being used. The drive element is not limited to the current amplification type, and may be a voltage control type using an FET or the like. Furthermore, the number of drive elements used in one drive circuit is not limited to one, and it goes without saying that a circuit configuration can be similarly achieved even when a plurality of drive elements are used in combination. Further, the exposure head is not limited to a fiber type, and may be a bundle of a plurality of LDs.

It is (a) side view and (b) top view which showed the example of schematic structure of exposure apparatus. It is the schematic circuit diagram which showed the structural example of LD drive circuit. It is an external view of a drive element. It is a conceptual diagram of LD drive unit. It is the schematic circuit diagram which showed the other structural example of LD drive circuit. FIG. 10 is a schematic circuit diagram showing still another configuration example of the LD drive circuit. FIG. 10 is a schematic circuit diagram showing still another configuration example of the LD drive circuit. FIG. 10 is a schematic circuit diagram showing still another configuration example of the LD drive circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exposure apparatus 10 Main stand 11 Rail 20 Rotating drum 21 Rotating drum surface 22 Strut 23 Rotating shaft 30 Recording material 40 Light source (LD)
41 LD mounting base 42 Leg 50 Electronic cooling element (Peltier element)
51 Air cooling fan 60 Exposure head 61 Optical fiber 62 Lens 63 Moving table 65 Moving table 70 LD driving circuit 101 Operational amplifier 102 Driving element 103 Driving power source 110 Reference resistance element 111, 112 Feedback circuit 120 Connector 121 LD
122 metal case 123 metal wire 124 ground end 125 heat sink 130 drive power supply 131 ground end 140 drive power supply 141 drive element 142 reference resistance element 143 LD
144 Metal wire 145 Metal case 146 Ground terminal 150, 151 Feedback circuit 160 Drive power supply 161 Ground terminal 170 Operational amplifier 171 Control power supply 172 Control power supply 173 Drive power supply

Claims (7)

  An LD drive unit comprising a plurality of LDs and a drive circuit for driving the LDs with a constant current control by a drive element, wherein either one of an anode or a cathode of the LD is connected to a case of the LD, The case is connected to either the LD driving power source or GND, one of the terminals of the driving element is a heat sink, and the heat sink is the other one of the LD driving power source or GND. And an LD driving unit having the same circuit configuration for all of the plurality of LDs.   2. The LD driving unit according to claim 1, wherein a heat sink is not connected to the heat radiating plate.   The LD driving unit according to claim 1, wherein all of the cases have the same potential.   The LD driving unit according to any one of claims 1 to 3, wherein all of the cases are electrically connected to each other.   6. The LD driving unit according to claim 1, wherein the driving circuit control power source and the LD driving power source are separately and independently.   An LD drive unit comprising a plurality of LDs and a drive circuit for driving the LDs with constant current control by a drive element, wherein one end of a reference resistance element of the drive circuit is connected to a collector or emitter of the drive element One of the heat sinks is connected to one feedback circuit for constant current control, and the other end of the reference resistance element is connected to either the cathode or the anode of the LD. The other feedback circuit for constant current control is connected, and the other one of the collector or emitter, which is a heat sink, is connected to either the LD driving power supply or GND, The other one of the cathode and the anode is connected to the other power source for driving the LD or the other of the GND, and connected to the plurality of LDs. LD drive unit, characterized in that Te is the same circuit configuration. An exposure apparatus comprising the LD drive unit according to claim 1.

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