JP2006334893A - Image recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image recorder which carries out highly fine recording at a high speed by performing efficient exposure while enlargement of the apparatus and an increase of apparatus costs are suppressed even if exposure channels of a part of exposure heads fail in the case where exposure is carried out by a plurality of the exposure heads. <P>SOLUTION: The image recorder is equipped with: a rotary drum driving mechanism 8 which scans light beams L in a main scanning direction X; the plurality of exposure heads 5 which include exposure light sources 10, lenses 14 and a linear motor 21 and have a plurality of the exposure channels; a linear encoder 27 which detects a position of the exposure head 5 and a moving speed in a sub scanning direction Y of the exposure head 5; a quantity of light measuring mechanism 39 which measures a quantity of light of the light beams L; and a control part 35 which judges whether the exposure channels are usable, and controls the linear motor 21 to change an interval between the exposure heads 5 and the moving speed in the sub scanning direction Y of the exposure head 5 in accordance with the number of the usable exposure channels continuous among the exposure channels at each exposure head 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus that records an image by irradiating an exposure surface of a recording material with a light beam from an exposure light source.

  Conventionally, in a printing apparatus or the like, an image recording apparatus that records an image by subjecting a recording material to light exposure is used. Such an image recording apparatus, for example, irradiates an exposure surface of a recording material with a light beam from an exposure light source composed of a light emitter such as an LED or a laser through an optical system including a lens or the like. A light beam is imaged to thereby record an image on a recording material.

  Such an image recording apparatus includes an outer surface scanning type in which a recording material is wound around the outer peripheral surface of the drum and light is irradiated from the outside of the drum, and an inner peripheral surface of the drum. And an inner surface scanning type in which an exposure head for exposure is provided inside the drum and the recording material is exposed by irradiating light from the inside of the drum.

  By the way, in recent years, it has been desired to increase the recording speed of an image recording apparatus, and the recording speed of an image recording apparatus that records an image by subjecting a recording material to light exposure is the exposure channel of an exposure head that irradiates light. Depends on the number. For this reason, means for increasing the number of exposure channels is taken in order to increase the recording speed. That is, in the case of the outer surface scanning method, for example, a method of increasing the number of exposure channels by guiding light beams from a plurality of light sources by optical fibers and bundling the optical fibers and arranging them in an array (see, for example, Patent Document 1). Or a method of increasing the number of exposure channels by branching the light emitted from the light source into a plurality of light beams and modulating the plurality of light beams individually by a spatial modulation element and forming an image on the surface of the recording material (See, for example, Patent Document 2). Further, in the case of the inner surface scanning method, for example, by providing means for performing main scanning by rotating a light beam with a so-called rotating polygon mirror or the like, multiple beam scanning can be performed even in a limited space inside the drum. A method has been proposed (see, for example, Patent Document 3).

  However, when the number of exposure channels in one exposure head is increased as described above, it is difficult to accurately perform light exposure by accurately arranging the light irradiation positions of the exposure channels. In addition, since many light sources are concentrated on the exposure head, the temperature of the exposure head is increased. In addition, as the number of exposure channels increases, the optical elements such as lenses for focusing the light have to be increased in size, and distortion tends to occur. To raise. Furthermore, in an image recording apparatus that irradiates light by scanning an exposure head in the sub-scanning direction while rotating a drum around which a recording material is wound in the main scanning direction, an image is generally obtained while performing sub-scanning at a constant speed. In order to perform exposure, the main scanning line is not perpendicular to the sub-scanning direction but has an inclination. The inclination angle increases as the number of exposure channels increases. For this reason, there is a problem that a recorded image is shifted.

In view of this, an image recording apparatus has been proposed in which a plurality of exposure heads having a relatively small number of exposure channels are arranged in the sub-scanning direction (see, for example, Patent Document 4). As described above, when a plurality of exposure heads are arranged, the recording speed can be increased without increasing the size of the lens or the like.
JP 2000-141749 A JP-A-8-90831 Japanese Patent Laid-Open No. 5-5846 JP 2003-330200 A

  By the way, in the image recording apparatus described in Patent Document 4, for example, the exposure heads are arranged at regular intervals, and the exposure heads are arranged in the sub-scanning direction by a ball screw mechanism while the interval between the exposure heads is fixed. It is supposed to move. In Patent Document 4, when some of the exposure channels of a plurality of exposure heads fail and become unusable, the number of exposure channels used for exposure of all the exposure heads has failed. The number of exposure channels that can be used is disclosed.

  However, if the number of exposure channels of all the exposure heads is adjusted to the number of usable channels of the exposure head that has failed in this way, the exposure head that has not failed cannot be fully utilized, and efficient. Exposure cannot be performed. For this reason, there is a problem that the time required for image recording becomes longer than necessary.

  Further, if each exposure head is provided with a ball screw mechanism for moving the exposure head so that each exposure head can be moved separately, there is a problem that the entire apparatus becomes large and the apparatus cost increases.

  Therefore, the present invention has been made to solve the above-described problems. When exposure is performed with a plurality of exposure heads, the size of the apparatus is increased even if the exposure channels of some exposure heads fail. Another object of the present invention is to provide an image recording apparatus capable of performing efficient exposure and performing high-speed and high-definition recording while suppressing an increase in apparatus cost.

In order to solve such a problem, the invention described in claim 1 includes main scanning means for scanning the light beam in the main scanning direction,
An exposure light source that irradiates the light beam, an optical system that forms an image of the light beam emitted from the exposure light source on an exposure surface of a recording material, and a sub-scanning direction that is substantially perpendicular to the main scanning direction. A plurality of exposure heads having a plurality of exposure channels;
A head detection mechanism for detecting a position of the exposure head and a moving speed of the exposure head in the sub-scanning direction;
A light quantity measuring mechanism for measuring the light quantity of the light beam emitted from the exposure head;
Based on the measurement result of the light quantity measurement mechanism, it is determined whether or not the exposure channel can be used, and each of the exposure channels for each exposure head can be used according to the number of consecutive usable exposure channels. And a controller that controls the head moving mechanism so as to change the interval between the exposure heads and the moving speed of the exposure head in the sub-scanning direction.

  The invention according to claim 1 having such a configuration moves a plurality of exposure heads including an exposure light source and an optical system such as a lens in a sub-scanning direction by a head moving mechanism, and a light beam by a main scanning unit. When the image is recorded by scanning in the main scanning direction, the position of the exposure head and the moving speed of the exposure head in the sub-scanning direction are detected by the head detection mechanism, and the control unit controls the head moving mechanism, and the exposure head The interval between the exposure heads and the moving speed of the exposure heads in the sub-scanning direction are changed in accordance with the number of consecutive usable exposure channels among the exposure channels.

  According to a second aspect of the present invention, in the image recording apparatus according to the first aspect, the control unit includes a ratio of recording widths of the exposure heads in the sub-scanning direction and the sub-scanning of the exposure heads. The distance between the exposure heads and the movement of the exposure heads in the sub-scanning direction so that the ratio of the moving speeds in the directions is substantially the same as the ratio of the number of consecutive usable exposure channels of the exposure heads. The head moving mechanism is controlled so as to change the speed.

  According to the second aspect of the present invention having such a configuration, the ratio of the recording width of each exposure head in the sub-scanning direction and the ratio of the moving speed of each exposure head in the sub-scanning direction can be used continuously. The controller moves the exposure head by controlling the head moving mechanism so as to change the interval between the exposure heads and the moving speed of each exposure head in the sub-scanning direction so that the ratio of the number of exposure channels is substantially the same. It is supposed to let you.

  According to a third aspect of the present invention, in the image recording apparatus according to the first or second aspect, the controller is configured such that the interval between the exposure heads is a pixel pitch of pixels recorded by the exposure head. And the head moving mechanism is controlled so as to be an integral multiple of the product of the number of exposure channels continuously available for the exposure head located upstream of the exposure head in the sub-scanning direction. Yes.

  According to the third aspect of the present invention having such a configuration, the interval between the exposure heads is such that the pixel pitch of the pixels recorded by the exposure head and the exposure heads positioned upstream of the exposure head in the sub-scanning direction are continuous. The control unit moves the exposure head by controlling the head moving mechanism so as to be an integral multiple of the product of the number of exposure channels that can be used.

  According to a fourth aspect of the present invention, in the image recording apparatus according to any one of the first to third aspects, the head moving mechanism includes a magnet as a stator and an electromagnetic coil as a mover. The electromagnetic coil is individually installed in each of the exposure heads.

  According to a fourth aspect of the present invention, a linear motor having a magnet as a stator and an electromagnetic coil as a mover is used as a head moving mechanism, and each exposure head is provided with an electromagnetic coil individually. Can be moved independently.

  According to the first aspect of the invention, since image recording is performed using a plurality of exposure heads, the number of exposure channels provided in one exposure head can be reduced, and the irradiation positions of the exposure channels can be arranged with high accuracy. In addition, the influence of the inclination of the main scanning line with respect to the sub scanning direction caused by scanning the exposure head in the sub scanning direction while rotating the drum around which the recording material is wound in the main scanning direction can be reduced. In addition, since many light sources are not concentrated on the exposure head, the temperature of the exposure head does not rise more than necessary. Further, since the number of exposure channels provided in one exposure head is relatively small, it is not necessary to increase the size of a lens or the like for focusing light, and the apparatus cost can be suppressed.

  Further, when image recording is performed using a plurality of exposure heads as described above, the interval between the exposure heads and the sub-scanning direction of the exposure heads according to the number of consecutive usable exposure channels among the exposure channels for each exposure head. Because the movement speed of the camera is changed, even if the exposure channels of some exposure heads fail, image recording can be performed efficiently using all exposure heads, and high-definition image recording can be performed in a short time. The effect is that it becomes possible.

  According to the second aspect of the present invention, the distance between the exposure heads is such that the ratio of the recording width of each exposure head in the sub-scanning direction and the ratio of the moving speed of each exposure head in the sub-scanning direction are continuous for each exposure head. Since the ratio is adjusted to be almost the same as the ratio of the number of usable exposure channels, even if the exposure channels of some of the exposure heads fail, image recording can be performed using all the exposure heads efficiently. It is possible to achieve high-definition image recording in a short time.

  According to the third aspect of the present invention, the interval between the exposure heads can be continuously used by the recording width of each exposure head in the sub-scanning direction and the exposure head positioned upstream of the exposure head in the sub-scanning direction. Since the adjustment is made to be an integral multiple of the product of the number of exposure channels, it is always when the distance between the exposure heads is adjusted according to the number of exposure channels that can be continuously used among the exposure channels for each exposure head. The interval can be separated by a divisible length. For this reason, it is possible to perform image recording using each exposure head efficiently without waste, so that it is possible to perform high-definition image recording in a short time.

  According to the fourth aspect of the present invention, since the exposure head is moved using the linear motor, the exposure head can be smoothly moved as compared with the case where the ball screw mechanism is used, and vibration during movement is achieved. This makes it possible to perform high-definition image recording.

  When the exposure head is moved using a ball screw mechanism, the movement distance and movement speed of the exposure head are grasped from the number of rotations of the screw, etc., whereas in the case of a linear motor, the position of the exposure head is detected by a linear encoder. In addition, since the movement speed can be accurately grasped, more accurate control can be performed.

  Furthermore, since each exposure head is provided with an electromagnetic coil individually, each exposure head can be moved independently, and the distance between the exposure heads and the moving speed of the exposure head in the sub-scanning direction are individually adjusted. Is possible. Further, when the ball screw mechanism is used, if the distance between the exposure heads and the moving speed of the exposure head in the sub-scanning direction are separately adjusted, it is necessary to provide a ball screw for each exposure head. In the case of a linear motor, the distance between the exposure heads and the movement speed of the exposure heads in the sub-scanning direction are adjusted by a simple and inexpensive method in which each exposure head is provided with an electromagnetic coil. There is an effect that can be.

  Hereinafter, an embodiment of an image recording apparatus according to the present invention will be described with reference to FIGS.

  In this embodiment, the image recording apparatus 1 is a CTP (Computer to Plate) output apparatus that directly records an image on a printing plate as a recording material 4 having an exposure surface exposed by light, for example.

  As shown in FIG. 1 and FIG. 2, an apparatus base 2 for fixing each member for performing image recording is provided inside the image recording apparatus 1. The apparatus base 2 has a substantially cylindrical rotating drum 3 holding the recording material 4 on the outer peripheral surface, and a plurality of recording materials 4 supported on the rotating drum 3 by exposing the recording material 4 to a plurality of images. An exposure head 5 is provided.

  The rotating drum 3 includes a rotating shaft 6 provided so as to be substantially concentric with the central axis of the rotating drum 3. The rotating shaft 6 is pivotally supported by a support member 7 erected on the apparatus mount 2. The rotating drum 3 can be rotated at a constant speed in the main scanning direction X that is the circumferential direction of the rotating drum 3 by rotating the rotating shaft 6 by a rotating drum driving mechanism 8 (see FIG. 6) as main scanning means. Yes.

  As the recording material 4 held on the rotary drum 3, for example, a silver salt sensitive material, a heat mode recording material or the like can be used, but the recording material 4 is not limited to the one exemplified here.

  Next, the exposure head 5 includes a head support 9 that supports each part of the exposure head 5. As shown in FIGS. 1 to 3, an exposure light source 10 configured by a light emitter such as a semiconductor laser or an LED (light emitting diode) is opposed to the rotating drum 3 on the head support 9. Several are fixed so that.

  Each exposure light source 10 is connected to an optical fiber 12 that transmits a light beam L emitted from the exposure light source 10, and these optical fibers 12 are bundled together to form an optical fiber array 13. A lens 14 is disposed on the optical axis of the light beam L emitted from the optical fiber array 13 as an optical system for forming an image of the light beam L on the exposure surface of the recording material 4. As the lens 14, either a single lens or a lens group configured by combining a plurality of lenses may be used.

  Each exposure light source 10 forms one exposure channel via the optical fiber array 13, and one exposure channel corresponds to the recording width of one pixel in image recording. Each light beam L emitted from each exposure light source 10 performs recording with a width of one pixel.

  As shown in FIGS. 1 and 2, a long shaft-like stator 15 constituting a linear motor 21 as a head moving mechanism for moving the head support 9 is rotated on the apparatus base 2. The drum 3 extends in the width direction of the rotary drum 3 so as to be substantially parallel to the rotary shaft 6 of the drum 3. As shown in FIG. 4, the stator 15 includes a substantially pipe-shaped member 16 in which a plurality of magnets 17 having a substantially circular cross section are connected so that N poles or S poles face each other. Is. Both ends of the stator 15 are supported by a stator support member 18 fixed to the device mount 2.

  The magnet 17 used for the stator 15 is preferably a rare earth magnet having a high magnetic flux density. In particular, a neodymium magnet such as a neodymium-iron-boron magnet (Nd—Fe—B magnet) is preferably used as the rare earth magnet. When such a rare earth magnet is used for the stator 15 of the linear motor 21, a high thrust can be obtained as compared with the case of using another magnet. In addition, the magnet 17 is not limited to what was illustrated here, Another magnet can also be used.

  The pipe-shaped member 16 is formed of a nonmagnetic material such as an aluminum alloy, a copper alloy, or nonmagnetic stainless steel. The pipe-like member 16 is preferably as thin as possible so as not to reduce the magnetic field generated from the magnet 17 accommodated therein. For example, the pipe-shaped member 16 is made of stainless steel having a thickness of 1 mm. In addition, the material which forms the pipe-shaped member 16 is not limited to what was illustrated here.

  An electromagnetic coil 19 and an electromagnetic coil 19 are held at a position opposite to the side on which the exposure light source 10 and the like of the head support base 9 are provided and corresponding to the stator 15. A mover 22 is provided which constitutes the linear motor 21 with a coil holding member 20 to be fixed. The coil holding member 20 may not cover the entire electromagnetic coil 19 as long as it can hold at least a part of the electromagnetic coil 19 and fix the electromagnetic coil 19 to the head support base 9.

  As shown in FIG. 4, the electromagnetic coil 19 is a hollow coil group in which a plurality of coils 23 are wound, and includes a plurality of phases such as three phases, but the electromagnetic coil 19 is not limited to this. As for the number of turns of the electromagnetic coil 19, it is preferable to determine an appropriate number of turns and a winding diameter so that a thrust greater than the desired thrust can be obtained. In addition, the electromagnetic coil 19 is not limited to the structure illustrated here, For example, it is good also as a structure provided with a hollow bobbin and winding the coil 23 around this bobbin.

  The stator 15 penetrates through the hollow portion of the electromagnetic coil 19, and the stator 15 and the movable element 22 constitute a linear motor 21.

  The linear motor 21 generates a magnetic field (N pole, S pole) in the electromagnetic coil 19 when a current is supplied to the electromagnetic coil 19 of the mover 22 from a power source (not shown), and the pipe member 16 of the electromagnetic coil 19 and the fixed 15. A thrust is generated by generating an attractive force and a repulsive force between the magnet 17 and the magnet 17 arranged linearly therein, and the exposure head 5 is referred to as a longitudinal direction of the stator 15 (hereinafter referred to as “sub-scanning direction Y”). ) To move. In addition, the direction of the thrust of the linear motor 21 changes depending on the direction of the current flowing from the power source, and the moving direction of the exposure head 5 can be switched by switching the direction of the current flowing from the power source. . Further, the linear motor 21 can change the magnitude of the thrust according to the magnitude of the current supplied from the power source, and the moving speed of the exposure head 5 can be changed by changing the magnitude of the current.

  Note that there is a minute gap between the outer peripheral surface of the stator 15 and the inner peripheral surface of the electromagnetic coil 19, and the electromagnetic coil 19 may partially slide on the outer peripheral surface of the stator 15, or may slide It is also possible to move while keeping the gap without doing so.

  By using the cylindrical magnet 17 as shown in the present embodiment, the manufacturing cost of the magnet 17 can be reduced, and the stator 15 made of the cylindrical magnet 17 is made to penetrate the electromagnetic coil 19. The use efficiency of the magnetic flux is good, and a large thrust can be obtained without increasing the size of the stator 15 more than necessary. Note that the configuration of the linear motor 21 as the head moving mechanism for moving the exposure head 5 is not limited to the one exemplified here, and a linear motor including a stator and an electromagnetic coil having other shapes may be used.

  A guide rail 24 for guiding the exposure head 5 is provided on the apparatus base 2 so as to be substantially parallel to the stator 15. Both ends of the guide rail 24 are supported by rail support members 25 fixed to the device mount 2. A guide member 26 having a hollow portion through which the guide rail 24 passes is provided at a position corresponding to the guide rail 24 on the surface on which the movable element 22 of the head support 9 is provided. The guide member 26 is slidable along the guide rail 24, so that the exposure head 5 reciprocates along the sub-scanning direction Y when the movable element 22 moves along the stator 15. 26 supports the exposure head 5.

  Further, an encoder scale 28 constituting a linear encoder 27 as a head detection mechanism for detecting the position of the exposure head 5 and the moving speed in the sub-scanning direction Y is provided on the apparatus base 2 with the stator 15 and the guide rail 24. It extends in the sub-scanning direction Y so as to be parallel. Further, an optical sensor 29 for detecting encoder scale information is provided at a position facing the encoder scale 28 on the surface of the head support 9 where the mover 22 is provided so as to face the encoder scale 28. It has been.

  The encoder scale 28 is, for example, an optical reflective scale, and a light high reflectance surface and a light low reflectance surface are alternately arranged at a predetermined interval in the sub-scanning direction Y that is the moving direction of the exposure head 5. .

  As shown in FIG. 5, the optical sensor 29 includes a light source 31 configured by a light emitting element such as an LED and irradiating light to the encoder scale 28, and a scanning grating 32 in which two phase gratings are alternately fitted. A condenser lens 33 for condensing the light emitted from the light source 31 and reflected by the encoder scale 28; and a light receiving element 34 for receiving the reflected light collected by the condenser lens, which is constituted by a photodiode, a phototransistor, or the like. ing. The optical sensor 29 can move with the exposure head 5 while facing the encoder scale 28.

  The light emitted from the light source 31 passes through the condenser lens 33 to become a bundle of parallel light, and is irradiated onto the encoder scale 28 via the scanning grating 32. The light is reflected by the encoder scale 28, and the reflected light is received by the light receiving element 34 through the scanning grating 32 and the condenser lens 33. When the light from the condenser lens 33 passes through the scanning grating 32, for example, four grating images each having a graduation interval of ¼ are formed on the surface of the encoder scale 28, and the reflected light is transmitted to the light receiving element 34. A four-phase sine wave signal having a phase difference of approximately 90 degrees is generated upon incidence. When the optical sensor 29 moves on the encoder scale 28, the light receiving element 34 receives the reflected light from the encoder scale 28 at any time, detects the intensity (luminous intensity, light quantity, etc.) of the reflected light and responds to the received light. An encoder signal is generated.

  The encoder scale 28 is not limited to the one exemplified here, and for example, a portion having a high light transmittance and a portion having a low light transmittance are alternately arranged at a predetermined interval in the sub-scanning direction Y that is the moving direction of the exposure head 5. It is also possible to apply an equation scale. When such a transmissive encoder scale is used, the intensity of transmitted light that passes through the encoder scale is detected by an optical sensor.

  Further, a light quantity measuring mechanism 39 that measures the light quantity of the light beam L emitted from the exposure light source 10 of the exposure head 5 is located in the vicinity of the rotary drum 3 and capable of receiving the light emitted from the exposure head 5. Is provided. The light quantity measuring mechanism 39 is, for example, a photosensor (not shown) that receives the light beam L emitted from the exposure light source 10, and A / D conversion of an analog signal corresponding to the light quantity of the light beam L detected by the photosensor. It comprises an A / D converter (not shown) to be performed. The light quantity measuring mechanism 39 may be any mechanism that can receive the light emitted from the exposure head 5 and measure the light quantity, and the configuration is not limited to the one exemplified here. 1 illustrates an example in which one light quantity measuring mechanism 39 is provided. However, the number of the light quantity measuring mechanisms 39 is not limited to this. For example, one light quantity measuring mechanism 39 may be provided on each side of the rotating drum 3. .

  As shown in FIG. 6, the image recording apparatus 1 includes, for example, a CPU (Central Processing Unit) 36, a ROM (Read Only Memory) 37 as storage means for storing various programs, and a RAM (Random Access). Memory) 38 is provided. The control unit 35 reads a predetermined program stored in the ROM 37 and develops it in the work area of the RAM 38, and the CPU 36 executes various processes according to the program.

  The RAM 38 has a work memory area (not shown) that stores various programs designated by the CPU 36, various data, processing results, and the like. The CPU 36 reads a designated program from the system programs and various application programs stored in the ROM 37, stores it in the work memory area in the RAM 38, and executes various processes in accordance with the program stored in the RAM 38. At the same time, the processing result is stored in a work memory area in the RAM 38.

  The light quantity of the light beam L received by the light quantity measurement mechanism 39 is converted into a signal and sent to the control section 35. The control section 35 is based on the light quantity data at the time of exposure sent from the light quantity measurement mechanism 39. Thus, it is determined whether there is an exposure channel that cannot be used for light exposure, such as an exposure channel of the exposure head 5 that is not lit or that has a small amount of light.

  Further, in the present embodiment, the ROM 37 stores the appropriate distance between the exposure heads 5 and the sub-scanning of the exposure heads 5 based on, for example, the number of continuous usable exposure channels among the exposure channels for each exposure head 5. Head movement calculation program for calculating the moving speed in the direction Y, and LUT (Look Up Table) that associates the relationship between the number of continuous usable exposure channels of the exposure head 5, the distance between the exposure heads 5 and the moving speed data. Etc. are stored. Note that the location where the LUT is stored is not limited to the ROM 37.

  Image data is transmitted to the image recording apparatus 1 from an external device, and the transmitted image data is temporarily stored in the RAM 38 of the control unit 35. Further, an encoder signal is sent from the optical sensor 29 of the linear encoder 27 provided in each exposure head 5 to the control unit 35, and the control unit 35 receives each exposure head 5 from the sent encoder signal. And the moving speed in the sub-scanning direction Y are grasped.

  When the image data is sent from the external device, the control unit 35 determines the recording width of the image from the sent image data, and then reads the head movement calculation program from the ROM 37 and continuously uses the exposure channels for each exposure head. The appropriate distance between the exposure heads 5 and the moving speed of the exposure head in the sub-scanning direction Y are calculated according to the number of possible exposure channels.

  Here, the appropriate distance between the exposure heads 5 according to the number of exposure channels that can be used continuously among the exposure channels for each exposure head 5 is the ratio of the recording width of each exposure head 5 in the sub-scanning direction Y. The ratio of the number of consecutive usable exposure channels of each exposure head 5 is substantially equal, and the interval between the exposure heads 5 is the pixel pitch of the pixels recorded by the exposure head 5 and the sub-scan of the exposure head 5 respectively. This is a distance that is an integral multiple of the product of the number of exposure channels that can be continuously used by the exposure head 5 located upstream in the direction Y. The pixel pitch of the pixels recorded by the exposure head 5 refers to the width from the center of one pixel recorded by an exposure channel of the exposure head 5 to the center of one pixel recorded by an adjacent exposure channel. The width of one pixel recorded by one exposure channel of the exposure head 5 and the number of exposure channels of each exposure head 5 may be stored in advance in the ROM 37 or the like, or may be set as appropriate by the operator. .

  Further, the moving speed of the exposure head 5 in the sub-scanning direction Y is such that the ratio of the moving speeds of the exposure heads 5 in the sub-scanning direction Y is substantially equal to the ratio of the number of continuous usable exposure channels of the respective exposure heads 5. To be determined.

  For example, as shown in FIG. 7, when there are two exposure heads 5 and the exposure channels of each exposure head 5 are 32 channels, the 16th exposure channel of one exposure head 5 is not lit and used. In the case where the control unit 35 determines that it cannot be performed, how the distance between the exposure heads 5 and the moving speed of the exposure head 5 in the sub-scanning direction Y are determined will be described below.

  In this case, the number of exposure channels that can be continuously used by the exposure head 5 having a failure is 16 channels from the 17th to the 32nd. Therefore, the ratio of the number of consecutive usable exposure channels of the exposure head 5 without failure to the number of consecutive usable exposure channels of the exposure head 5 with failure is 32:16, that is, 2: 1. . Therefore, the ratio of the recording widths of the exposure heads 5 in the sub-scanning direction Y is 1 for the exposure head having a failure with respect to 2 for the exposure head having no failure, and the interval between the exposure heads 5 is 5. For each exposure head 5 is a distance that is an integral multiple of the product of the pixel pitch of the pixels recorded by the above and the number of consecutive usable exposure channels of the exposure head 5 located upstream of the exposure head 5 in the sub-scanning direction Y, respectively. The appropriate distance between the exposure heads 5 corresponds to the number of consecutive usable exposure channels among the exposure channels. In the above example, the exposure head 5 without failure records twice the recording width of the exposure head with failure, so the exposure head 5 without failure is twice as large as the exposure head with failure. At a speed corresponding to 2: 1 which is the ratio of the number of consecutive usable exposure channels of the exposure head 5 without failure to the number of consecutive usable exposure channels of the exposure head 5 with failure. The moving speed in the sub-scanning direction Y is determined so as to move in the sub-scanning direction Y.

  Further, the control unit 35 drives the linear motor 21 by causing a current to flow through the electromagnetic coil 19 of the linear motor 21 to reciprocate the exposure head 5 in the sub-scanning direction Y.

  The control unit 35 controls the rotary drum drive mechanism 8 to rotate the rotary drum 3 holding the recording material 4 in the main scanning direction X at a constant speed.

  Further, the control unit 35 outputs an exposure control signal to the exposure control circuit 11 according to the image information, thereby controlling the exposure light source 10 of the exposure head 5 and appropriately responding to the exposure control signal from each exposure head 5. It is designed to emit light.

  Next, the operation of the image recording apparatus according to this embodiment will be described.

  When image data is sent from an external device, the image data sent by the control unit 35 is temporarily stored in the RAM 38.

  Before starting the image recording, the light amount measurement mechanism 39 measures the light amount at the time of exposure of each exposure head, and the control unit 35 determines the exposure head of the exposure head based on the light amount data at the time of exposure sent from the light amount measurement mechanism 39. It is determined whether there is an unusable exposure channel among the exposure channels. When there is an unusable exposure channel, the CPU 36 of the control unit 35 has a failure with the exposure head 5 without a failure based on the number of usable exposure channels of the exposure head 5 without a failure and the exposure head 5 with a failure. A ratio with the number of usable exposure channels of the exposure head 5 is calculated.

  Then, the CPU 36 of the control unit 35 reads the head movement calculation program from the ROM 37 and develops it in the work memory area of the RAM 38. Based on this head movement calculation program, the ratio of the recording widths of the exposure heads 5 in the sub-scanning direction Y is determined. Is substantially equal to the ratio of the number of consecutive usable exposure channels of each exposure head 5, and the interval between the exposure heads 5 is different from the pixel pitch of the pixels recorded by the exposure head 5 and each of the exposure heads 5. A distance that is an integral multiple of the product of the number of continuous usable exposure channels of the exposure head 5 positioned on the upstream side in the scanning direction Y depends on the number of continuous usable exposure channels among the exposure channels for each exposure head. The distance between the exposure heads 5 is calculated as an appropriate distance, and the ratio of the moving speeds of the exposure heads in the sub-scanning direction Y is calculated for each exposure head. Calculating a substantially equal speed and the ratio of the number of available exposure consecutive channels of de 5 as the moving speed in the sub-scanning direction Y of the exposure head.

  Next, the control unit 35 operates the linear motor 21 to appropriately move each exposure head 5 to a position where the interval between the exposure heads 5 becomes the appropriate distance. The position of each exposure head 5 is detected by a linear encoder 27, and the position information of each exposure head 5 is sent from the optical sensor 29 of the linear encoder 27 to the control unit 35 as an encoder signal as needed.

  When the exposure head 5 moves to a predetermined position, the image recording apparatus 1 performs light exposure on the exposed surface of the recording material 4 to form an image. When image recording is performed, the recording material 4 is held on the outer peripheral surface of the rotary drum 3 so that the exposure surface is on the outside, and the rotary drum driving mechanism 8 is operated by the control unit 35 so that the rotary drum 3 is main. Rotate in the scanning direction X.

  Then, under the control of the control unit 35, the light beam L is irradiated from the exposure light source 10, and the light beam L is imaged on the exposure surface which is the surface of the recording material 4 through the lens 14. Further, the control unit 35 operates the linear motor 21 to reciprocate the exposure head 5 in the sub scanning direction Y while rotating the rotary drum 3 in the main scanning direction X. At this time, the position of the exposure head 5 and the moving speed in the sub-scanning direction Y are detected by the optical sensor 29 of the linear encoder 27, and the position information of each exposure head 5 and the moving speed information in the sub-scanning direction Y are sent from the optical sensor 29 to the encoder. A signal is sent to the control unit 35 as needed. The control unit 35 grasps the position of each exposure head 5 and the moving speed in the sub-scanning direction Y from the encoder signal sent from the optical sensor 29, and linear motors according to the position of the exposure head 5 and the moving speed in the sub-scanning direction Y. The direction or intensity of the current flowing through the 21 electromagnetic coils 19 is switched. Thereby, sub-scanning is performed in which the exposure surface of the recording material 4 is sequentially light-exposed while appropriately switching the moving direction and moving speed of the exposure head 5 to record a predetermined image on the exposure surface of the recording material 4.

  As described above, according to the present embodiment, the distance between the exposure heads 5 is the ratio of the recording widths of the exposure heads 5 in the sub-scanning direction Y to the ratio of the number of exposure channels that can be continuously used by the exposure heads 5. And the interval between the exposure heads 5 can be continuously used by the pixel pitch of the pixels recorded by the exposure head 5 and the exposure head 5 positioned upstream of the exposure head 5 in the sub-scanning direction Y, respectively. And the ratio of the moving speed of each exposure head in the sub-scanning direction Y is the ratio of the number of consecutive usable exposure channels of each exposure head 5. The moving speed of each exposure head in the sub-scanning direction Y is adjusted so as to be substantially equal. Therefore, when image recording is performed using a plurality of exposure heads 5, each exposure head 5 can be efficiently scanned even if some exposure channels of the exposure head are faulty and cannot be used. Speeding up can be realized.

  Further, since the linear motor 21 is used as means for moving the exposure head 5 in the sub-scanning direction Y, even when a plurality of exposure heads 5 are provided, a ball screw mechanism or the like is used as moving means in the sub-scanning direction Y. In comparison, the apparatus is not increased in size, and the apparatus cost can be reduced. Further, the linear motor 21 moves more smoothly than the ball screw mechanism or the like, and controls the moving direction, moving distance, moving speed, etc. while detecting the position of the exposure head 5 by the linear encoder 27. Therefore, the position and moving speed of the exposure head 5 can be accurately grasped and sub-scanning can be performed, and high-definition image recording can be performed.

  In the present embodiment, the case where the two exposure heads 5 are arranged in the sub-scanning direction Y has been described as an example. However, the number of exposure heads 5 is not limited to the one shown here, and a plurality of exposure heads are also provided. 5 may be arranged side by side in the sub-scanning direction Y. In this case, each exposure head 5 is provided with a movable element 22 having an electromagnetic coil 19 and an optical sensor 29 constituting a linear encoder 27 so that each exposure head 5 can move independently. In this case, the ratio of the number of consecutive usable exposure channels of each exposure head 5 is calculated for all the exposure heads 5 arranged in the image recording apparatus.

  In the present embodiment, the distance between the exposure heads 5 is substantially equal to the ratio of the number of exposure channels that can be continuously used in each exposure head 5 in the sub-scanning direction Y. In addition, the ratio of the moving speeds of the exposure heads in the sub-scanning direction Y is substantially equal to the ratio of the number of consecutive usable exposure channels of each exposure head 5, and the interval between the exposure heads 5 is exposed. The condition is that it is an integral multiple of the product of the pixel pitch of the pixels recorded by the head 5 and the number of consecutive usable exposure channels of the exposure head 5 located upstream of the exposure head 5 in the sub-scanning direction Y, respectively. Although the exposure heads 5 are arranged so as to satisfy all of them, the distance between the exposure heads 5 can be used continuously by the ratio of the recording width of each exposure head 5 in the sub-scanning direction Y. And the ratio of the moving speeds of the respective exposure heads in the sub-scanning direction Y is substantially equal to the ratio of the number of consecutive usable exposure channels of each exposure head 5. An exposure head 5 may be arranged.

  In the present embodiment, the outer surface scanning type image recording apparatus 1 that performs image recording while holding the recording material 4 on the outer peripheral surface of the rotary drum 3 has been described. However, the present invention may be applied to other types of image recording apparatuses. It is possible to apply. For example, as shown in FIG. 8, a cylindrical fixed drum 41 capable of mounting a recording material 4 such as a photosensitive material is provided on the inner peripheral surface, and a light beam L is scanned inside the fixed drum 41 to perform image recording. The present invention can also be applied to an inner surface scanning type image recording apparatus including the exposure head 42.

  That is, the inner surface scanning type image recording apparatus is disposed inside the fixed drum 41 and a cylindrical fixed drum 41 to which a recording material 4 having an exposure surface on the inner peripheral surface can be mounted as shown in FIG. The plurality of exposure heads 42 are provided. The exposure head 42 includes an exposure light source 43 that includes a plurality of light emitters (not shown) that irradiate a light beam L, such as a semiconductor laser and an LED (light emitting diode), and has a plurality of exposure channels. On the exposure head 42 and on the optical path of the light beam L emitted from the exposure light source 43, a light reflecting element 45 that rotates about the central axis of the fixed drum 41 by a motor 46 that is a main scanning unit is provided. It has been. Further, a lens 44 as an optical system for focusing the light beam L and forming an image on the exposure surface of the recording material 4 is provided on the optical path of the light beam L and between the exposure light source 42 and the light reflecting element 45. Yes. Further, inside the fixed drum 41, a linear motor 51 as a head moving mechanism that is composed of a plurality of magnets (not shown) and moves the exposure head 42 in the longitudinal direction of the fixed drum 41 (hereinafter referred to as “sub-scanning direction”). A shaft-shaped stator 47 is provided so as to extend in the sub-scanning direction so as to be substantially parallel to the central axis of the fixed drum 41. A mover 48 constituting the linear motor 51 is installed at a position corresponding to the stator 47 of each exposure head 42. The mover 48 includes a hollow electromagnetic coil (not shown), and the stator 47 passes through the hollow portion of the mover 48. Since the configuration of the linear motor 51 is the same as that shown in the above embodiment, the description thereof is omitted. An encoder scale 49 of a linear encoder 50 as a head detection mechanism for detecting the position of the exposure head 42 and the like is provided in the fixed drum 41 so as to extend in the sub-scanning direction substantially in parallel with the stator 47. ing. An optical sensor (not shown) constituting the linear encoder 50 is provided at a position at one end of the exposure head 42 and facing the encoder scale 49. Further, a light amount measuring mechanism 52 that measures the light amount of the light beam L for each exposure channel is provided at a position on the inner end of the fixed drum 41 where the light beam L can be received. In addition, each part of the apparatus is centrally controlled by a control unit (not shown).

  In such an inner surface scanning type image recording apparatus, when information is sent from the light quantity measuring mechanism 52, the control unit determines whether or not each exposure channel is usable based on the information, and operates the linear motor 51. The ratio of the recording widths of the exposure heads 42 in the sub-scanning direction is substantially equal to the ratio of the number of continuous usable exposure channels of the exposure heads 42, and the interval between the exposure heads 42 is determined by the exposure heads 42. The exposure head is set to a distance that is an integral multiple of the product of the pixel pitch of the recorded pixels and the number of continuous usable exposure channels of the exposure head 42 located upstream of the exposure head 42 in the sub-scanning direction Y, respectively. 42 is moved appropriately. At this time, the position of the exposure head 42 is detected by the linear encoder 50, and the control unit determines whether the exposure head 42 has moved to an appropriate position based on information from the linear encoder 50.

  When each exposure head 42 moves to an appropriate position, the control unit irradiates the light beam L from the exposure light source 43 and starts image recording. That is, the light beam L emitted from the exposure light source 43 is reflected by the light reflecting element 45 and is focused by the focusing action of the lens 44 in the optical path, and the recording material 4 mounted on the inner peripheral surface of the fixed drum 41 is exposed. The image is formed on the surface. The light beam L is main-scanned by rotating the light reflecting element 45 by the motor 46, and sub-scanning is performed by driving a linear motor 51 as a head moving mechanism. When performing sub-scanning, the position of the exposure head 42 and the moving speed in the sub-scanning direction are detected by the linear encoder 50, and the control unit performs linear motor based on the position information of each exposure head 42 and the moving speed information in the sub-scanning direction Y. The intensity or direction of the current passed through 51 is switched. At this time, the control unit controls the linear encoder 50 so that the ratio of the moving speeds of the exposure heads 42 in the sub-scanning direction is substantially equal to the ratio of the number of exposure channels 42 that can be continuously used by the exposure heads 42. As a result, images are sequentially recorded on the exposure surface of the recording material 4.

  In the present embodiment, the CTP output device has been described as an example. However, the present invention can be applied to other devices as long as the device records an image by light exposure. For example, before creating a printing plate from a digital image signal, a proof that simulates an image obtained by printing on the printing plate created from the digital image signal is created and the digital image signal indicates In order to inspect the image for errors such as layout, color, characters, etc., and to check the printed matter in advance, use a device that creates a proof and a film that has taken a medical image. The present invention is also applicable to an exposure apparatus that performs exposure processing.

  In addition, it is needless to say that the present invention is not limited to the above embodiment and can be modified as appropriate.

It is the top view which showed typically the principal part of one Embodiment of the image recording apparatus which concerns on this invention. It is a side view of the principal part of the image recording apparatus shown in FIG. FIG. 2 is a perspective view showing a main part configuration of an exposure head of the image recording apparatus shown in FIG. 1. It is a perspective view which shows the principal part structure of the linear motor applied to the image recording apparatus shown to embodiment. It is a perspective view which shows the principal part structure of the linear encoder applied to the image recording apparatus shown to embodiment. It is a principal block diagram showing an outline of a control configuration of an embodiment of an image recording apparatus according to the present invention. It is the figure which showed typically the relationship between an exposure channel and the recording width of an image. It is the perspective view which showed typically the principal part of the modification of the image recording device shown to embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Rotating drum 4 Recording material 5 Exposure head 9 Head support stand 10 Exposure light source 12 Optical fiber 13 Optical fiber array 14 Lens 15 Stator 17 Magnet 19 Electromagnetic coil 21 Linear motor 22 Mover 24 Guide rail 26 Guide member 27 Linear encoder 28 Encoder scale 29 Optical sensor 35 Control unit 36 CPU
37 ROM
38 RAM
39 Light quantity measurement mechanism X Main scanning direction Y Sub scanning direction

Claims (4)

Main scanning means for scanning the light beam in the main scanning direction;
An exposure light source that irradiates the light beam, an optical system that forms an image of the light beam emitted from the exposure light source on an exposure surface of a recording material, and a sub-scanning direction that is substantially perpendicular to the main scanning direction. A plurality of exposure heads having a plurality of exposure channels;
A head detection mechanism for detecting the position of the exposure head and the moving speed of the exposure head in the sub-scanning direction;
A light quantity measuring mechanism for measuring the light quantity of the light beam emitted from the exposure head;
Based on the measurement result of the light quantity measurement mechanism, it is determined whether or not the exposure channel can be used, and each of the exposure channels for each exposure head can be used according to the number of consecutive usable exposure channels. An image recording apparatus comprising: a control unit that controls the head moving mechanism so as to change an interval between exposure heads and a moving speed of the exposure head in the sub-scanning direction.   The control unit is configured such that a ratio of a recording width of each exposure head in the sub-scanning direction and a ratio of a moving speed of each exposure head in the sub-scanning direction are the number of exposure channels that can be continuously used by each exposure head. 2. The head moving mechanism is controlled so as to change an interval between the exposure heads and a moving speed of the exposure heads in the sub-scanning direction so as to be substantially the same as the ratio of the above. The image recording apparatus described.   The controller is configured such that the interval between the exposure heads can be continuously used by the exposure heads located on the upstream side in the sub-scanning direction of the pixel pitch of the pixels recorded by the exposure heads. The image recording apparatus according to claim 1, wherein the head moving mechanism is controlled to be an integral multiple of a product of the number of exposure channels.   2. The head moving mechanism is a linear motor including a magnet as a stator and an electromagnetic coil as a mover, and each of the exposure heads is provided with the electromagnetic coil individually. The image recording apparatus according to claim 3.

Images