JPH062862U - Inner surface scanning type image recorder - Google Patents

Abstract

(57) [Abstract] [Purpose] To eliminate the error of the exposure position in the main scanning direction and improve the image recording accuracy. An exposure light beam B1 modulated by image data is applied to a photosensitive material 9 on the inner surface of a drum 3 via a galvanometer mirror 31. At this time, the galvano mirror 31 is rotationally driven about the central axis AX of the drum 3, and is moved in order from the predetermined origin position along the central axis AX direction together with the base 11. In this way, the photosensitive material 9 is scanned. Further, the clock light beam B2 is emitted toward the galvanometer mirror 31, and the reflected light of the light beam B2 from the linear encoder scale 45 via the galvanometer mirror 31 is detected by the light receiving element 44. A PLL circuit generates a pixel clock signal based on a pulse signal corresponding to the amount of reflected light output from the light receiving element 44, and the modulation timing of the light beam B1 by the multi-AOM 25 is
It is determined according to the pixel clock signal.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a cylindrical inner surface scanning type image recording apparatus which is used in, for example, the printing plate making industry and records an image by scanning a recording medium (for example, a photosensitive material) held on the inner surface of a cylindrical member with a light beam.

[0002]

[Prior art]

 Conventionally, a cylindrical inner surface scanning type image recording device is provided with a drum for holding a photosensitive material on the inner surface thereof, and a light beam emitted from a laser light source and modulated is reflected by an optical deflector toward the inner surface of the drum. It is known that the light deflector is rotated about the central axis of the drum to scan and expose the photosensitive material held on the inner surface of the drum.

An optical deflector used in such a cylindrical inner surface scanning type image recording apparatus is a reflection mirror tilted at 45 degrees, for example, and is rotated about a central axis of a drum by a scanning motor.

[0004]

[Problems to be solved by the device]

 However, in such a conventional cylindrical inner surface scanning type image recording apparatus, since the optical deflector is rotationally driven by the motor, due to the unevenness of the rotation speed of the motor, the main scanning direction (centering around the center axis of the drum) is caused. There was a problem that an error occurred in the exposure position in the rotating direction).

The cylindrical inner surface scanning type image recording apparatus of the present invention has been made in view of these problems. Therefore, it is an object of the present invention to improve the image recording accuracy by eliminating the error in the exposure position in the main scanning direction. And

[0006]

[Means for Solving the Problems] In order to achieve such an object, the following configuration is adopted as a means for solving the above problems.

That is, the cylindrical inner surface scanning type image recording apparatus of the present invention scans the inner surface of the cylindrical member with a light beam to expose the recording medium held on the inner surface to perform image recording. An image recording apparatus, comprising: first light beam output means for outputting a first light beam modulated according to an image to be recorded; and a first light beam output provided inside the cylindrical member. Light deflecting means for changing the traveling direction of the first light beam from the means toward the inner surface of the cylindrical member, and swinging or rotating the light deflecting means about the central axis of the cylindrical member, Scanning means for scanning and exposing the recording medium on the inner surface of the cylindrical member with a first light beam from the light deflecting means; and a light deflecting means arranged around the central axis of the cylindrical member, The reflection part An annular scale member, in which concealed portions are alternately and repeatedly formed, and a second light beam is output in the direction of the light deflector, so that the second scale beam is output toward the scale member via the light deflector. Second light beam output means for irradiating the second light beam, and a light detection means for receiving the second light beam reflected by the scale member via the light deflecting means and detecting a change in the light amount. And a control means for controlling the modulation timing of the first light beam of the first light beam output means based on the change of the light quantity detected by the light detection means. .

The cylindrical member in such a configuration does not necessarily have to be a cylindrical shape, and may be an arc-shaped member obtained by breaking the cylinder from the height direction.

[0009]

[Action]

 In the cylindrical inner surface scanning type image recording apparatus of the present invention configured as described above, the first light beam output means outputs the first light beam modulated according to the image to be recorded, and the scanning means. The optical deflecting means is swung or rotated about the central axis of the cylindrical member. As a result, the first light beam output from the first light beam output means is deflected in the direction toward the inner surface of the cylindrical member by the light deflection means, and the first light beam causes the recording medium on the inner surface of the cylindrical member to move. Scanned and exposed.

Further, the second light beam output means irradiates the second light beam toward the scale member via the light deflecting means, and the second light beam reflected by the scale member is converted into a light beam. Light is received by the light detection means via the deflection means. Since the scale member is formed by alternately repeating light-reflecting portions and light-shielding portions, the deflection of the light deflecting means is detected by detecting a change in the amount of light reflected from the scale member by means of a photodetector. You can know the corner. As a result, the modulation timing of the first light beam of the first light beam output means is controlled based on the detection result of the light detection means. Therefore, even if the deflection speed (change speed of the deflection angle) of the light deflector changes, the modulation timing of the light beam is controlled in accordance with the deflection speed, so that an error occurs in the exposure position in the main scanning direction. Nor.

[0011]

【Example】

 A preferred embodiment of the present invention will be described below in order to further clarify the configuration and operation of the present invention described above.

FIG. 1 is a perspective view showing a main part of an image recording apparatus as one embodiment of the present invention, and FIG. 2 is an enlarged perspective view showing the vicinity of an optical deflector of the image recording apparatus. As shown in FIG. 1, the image recording apparatus 1 includes an arc-shaped drum 3 obtained by breaking a cylinder from the height direction, and a scanning mechanism 5 inside the drum 3. The inner surface of the drum 3 is a vacuum suction surface, on which the photosensitive material 9 conveyed by a pair of sensitive material conveying rollers 7 is held, and the scanning mechanism 5 scans the inner surface of the drum 3. As a result, an image is recorded on the photosensitive material 9.

The scanning mechanism 5 includes a base 11 on which an optical system is mounted, a reciprocating mechanism 13 for reciprocating the base 11 in the axial direction of the drum 3 (z direction in the drawing), and a reciprocating mechanism 13 on the base 11. A light beam output unit 15 for sending a light beam (hereinafter, referred to as an exposure light beam) B1 for exposing the photosensitive material 9 is provided to the mounted optical system. The light beam output unit 15 includes a laser light source 21, a first lens 22, a beam splitter 23, an optical path length correction plate 24, a multi-modulator (for example, AOM) 25, a second lens 26, a third lens 27 and a reflection mirror 28. It is composed of the following items and is used as follows. The laser light source 21 is, for example, an argon laser, a helium neon laser, a semiconductor laser, or the like, and outputs a light beam having a wavelength that sensitizes the photosensitive material 9.

First, one exposure light beam B 1 emitted from the laser light source 21 in the −x direction in the drawing is converted into a converging beam by the first lens 22, and then a beam splitter 23 is used to It is divided into 20 light beams which are separated in the middle z direction. After that, the optical path lengths of the respective divided light beams are made equal by the optical path length correction plate 24 so that the beam wastes of the respective light beams can be formed in the multi-AOM 25. Then, each light beam is controlled by the multi AO M25 according to the image to be recorded on the photosensitive material 9, respectively. For example, on the photosensitive material 9, the light beam is turned on and exposed at the pixel to be recorded, and the light beam is turned off at the pixel not to be recorded. Each light beam thus modulated is made into a normal light having an appropriate thickness through the second lens 26 and the third lens 27, and then reflected by the reflection mirror 28 in the z direction in the figure.

The exposure light beam B1 reflected in the z direction is then reflected by the reflection mirror 30 fixed to the base 11 in a direction parallel to the xy plane in the figure and directed toward the central axis AX of the drum 3. It is reflected toward the optical system on the base 11. By the way, the surface of the base 11 is a plane parallel to the xy plane in the figure, and an optical system is provided on the surface. This optical system includes a galvano mirror 31 as an optical deflector that rotates around the central axis AX of the drum 3, a first condenser lens 32 and a first condensing lens 32 provided on the optical path from the reflection mirror 30 to the galvano mirror 31. And a half mirror 33.

The exposure light beam B 1 reflected by the reflection mirror 30 becomes a light beam having a condensing property by the first condenser lens 32, passes through the first half mirror 33 as it is, and is incident on the galvano mirror 31. To do. The incident light beam B1 is reflected toward the inside of the drum 3 by the galvanometer mirror 31. Since the galvano-mirror 31 receives the driving force of the main scanning motor 35 and rotates about the central axis AX of the drum 3, the exposure light beam B1 reflected by the galvano-mirror 31 causes the photosensitive material 9 to move to the main part. Scanning is performed in the scanning direction (rotational direction around the central axis AX of the drum 3). The irradiation position of the exposure light beam B1 on the galvanometer mirror 31 is such that a plurality of (20 in this embodiment) light beams forming the exposure light beam B1 are irradiated side by side in the z direction. Since it is at such a position, the scanning loci on the photosensitive material 9 by the respective light beams are perpendicular to the z direction, and as a result, image recording by the light beams of a plurality of channels becomes possible.

As an optical system on the base 11, a second laser light source 41, a second half mirror 42, a second condenser lens 43, a light receiving element 44 for detecting a light beam, and a linear encoder scale 45 are further provided. Is equipped with. Such a configuration is a configuration required to determine a clock signal as a timing signal when the light beam is modulated by the multi AOM 25, and these configurations will be described in detail below.

The second laser light source 41 is a semiconductor laser that outputs a light beam (hereinafter, referred to as a clock light beam) B 2 having a wavelength different from that of the exposure laser light source 21. Output in the direction to go. On the optical path from the second laser light source 41 to the first half mirror 33, a second half mirror 42 and a second condenser lens 43 are provided in order.

One clock light beam B 2 output from the second laser light source 41 passes through the second half mirror 42 as it is, and then the second condensing lens 43 condenses the light beam. And enters the first half mirror 33. The incident light beam B2 is reflected by the first half mirror 33 and then toward the galvano mirror 31.

By the way, a clock light beam B 2 from the second laser light source 41 reflected by the first half mirror 33 and an exposure light beam B 1 from the laser light source 21 transmitted through the first half mirror 33 Takes the optical path shown in FIG. 3 in detail. That is, as shown in FIG. 3, the exposure light beam B1 that has passed through the first half mirror 33 travels toward the galvanometer mirror 31 in a direction perpendicular to the z axis. On the other hand, the clock light beam B2 reflected at the point P2 above the transmission point P1 of the exposure light beam B1 is the first half mirror 33 in the traveling direction side of the clock light beam B2 with respect to the z-axis direction. Since it is tilted by a small angle θ, the light beam advances toward the galvanometer mirror 31 by tilting 2θ downward (−z direction) with respect to the direction perpendicular to the z axis.

The galvano mirror 31 reflects the thus-incident light beams B 1 and B 2 inward of the drum 3. By the way, in the galvano-mirror 31, the incident clock light beam B2 is incident from above from the direction perpendicular to the z-axis by an angle of 2θ with respect to the direction perpendicular to the z-axis. The exposure light beam B1 is reflected downward. A linear encoder scale 45 curved in an arc shape is provided around the center axis AX of the drum 3 in the reflection direction of the clock light beam B2.

The linear encoder scale 45 corresponds to a scale portion of a linear encoder that uses the second laser light source 41 as a laser light source, and slits at equal intervals (0.2 [mm] pitch in this embodiment) in the longitudinal direction. 45a is formed. On the back surface of the linear encoder scale 45, there is provided a reflection mirror 45b which is attached so as to be inclined so that the incident angle of the clock optical beam B2 from the galvanometer mirror 31 becomes 0 degree.

When the clock light beam B2 from the galvanometer mirror 31 is applied to the linear encoder scale 45, the clock light beam B2 is reflected by the reflection mirror 45b only when the irradiation position reaches the slit 45a. The light beam is emitted from the linear encoder scale 45.

The clock light beam B 2 reflected by the linear encoder scale 45 returns to the opposite direction on the incident path, is reflected by the galvanometer mirror 31 and the first half mirror 33, and is incident on the second half mirror 42. To do. The incident light beam is reflected by the second half mirror 42 toward the light receiving element 44. The light receiving element 44 detects a change in the light quantity of the clock light beam B2 reflected by the linear encoder scale 45, and outputs a pulse signal according to the change in the light quantity.

By the way, the above-mentioned optical system mounted on the base 11 reciprocates within the drum 3 in the central axis AX direction by the reciprocating mechanism 13 together with the base 11. The reciprocating mechanism 13 is a ball screw mechanism, and includes one screw rod 51 having a spiral screw thread and two guide rails 52 and 53, which are parallel to the central axis AX direction of the drum 3. It is installed in. The base 11 is screwed to the screw rod 51, and the rotary shaft of the sub-scanning motor 55 (FIG. 4) is connected to the end of the base 11. With this configuration, by driving the sub-scanning motor 55, the screw rod 51 rotates, and the base 11 is moved by being guided by the guide rails 52 and 53 by the screw rod 51.

As shown in FIG. 4, the image recording apparatus 1 further includes a scanning system control circuit 60 that controls the operations of the main scanning motor 35 and the sub scanning motor 55. The scanning system control circuit 60 drives the main scanning motor 35 by controlling the main scanning driving circuit 61, and drives the sub scanning motor 55 by controlling the sub scanning driving circuit 62. As a result, the galvanometer mirror 31 rotates at a constant speed around the center axis AX of the drum 3, and in parallel with this, the entire optical system including the galvanometer mirror 31 mounted on the base 11 has a predetermined center axis AX. It moves at a constant speed from the position in the specified direction (z direction or -z direction).

It should be noted that the scanning system control circuit 60 sends a signal indicating a control start timing or the like regarding the control of the main scanning motor 35 via the main scanning drive circuit 61 and the control of the sub scanning motor 55 via the sub scanning drive circuit 62. , To the image processing unit 70.

The image processing unit 70 is a device that generates image data to be sent to the image recording device 1. The image processing unit 70 receives an image signal captured by a one-dimensional storage type photoelectric conversion element (hereinafter referred to as CCD) 71 such as a CCD line sensor from A to A. The image data is fetched through the / D converter 72 and subjected to image processing, and the resulting image data is output to the multi AOM 25. The configuration is configured as an arithmetic logic circuit centering on the well-known CPU 70a, ROM 70b, RAM 70c, etc., and is input to the input port 70d to which the output signals from the A / D converter 72 and the scanning system control circuit 60 are input, and the multi AOM 25. An output port 70e for outputting image data is provided.

On the other hand, the pulse signal Sp output from the light receiving element 44 is input to a PLL (Phase Lock Loop) circuit 80. The PLL circuit 80 inputs the pulse signal Sp output from the light receiving element 44, multiplies the pulse signal by the number of pulses corresponding to the recording pixel density, and generates the pixel clock signal Sc. Sc is sent to the multi AOM 25 and the image processing unit 70.

An input image signal obtained by photoelectrically scanning an original image (not shown) by the CCD 71 is converted into multi-tone digital image data by the A / D converter 72 and stored in the RAM 70c in the image processing unit 70. Once stored. The image processing unit 70 appropriately reads out the stored image data, and performs a halftone dot generation process for creating a halftone dot (timing of generating an address from the screen pattern memory according to the pixel clock signal Sc from the PLL circuit 80). Image data Di1 to Di20 of a plurality of (20) channels, and each image data Di1 to Di20 is output to the multi-AOM 25. The image data Di1 to Di20 are binary data, and ON / OFF of the light beam is represented by 1 and 0 for each dot constituting the halftone dot. The multi-AOM 25 controls ON / OFF of the respective light beams B1 and B2 according to the image data D i1 to D i20. The timing of this on / off control is determined according to the pixel clock signal Sc from the PLL circuit 80.

In the image recording apparatus 1 configured as described above, the exposure light beam B1 modulated by the image data generated by the image processing unit 70 is transferred to the inner surface of the drum 3 via the galvano mirror 31. It is irradiated toward. At this time, the galvano mirror 31 is rotationally driven about the central axis AX of the drum 3 by the main scanning motor 35, and is moved in order from the predetermined origin position along the central axis AX direction together with the base 11. Therefore, the inner surface of the drum 3 is sequentially exposed in a spiral shape, and an image is recorded on the photosensitive material 9 held on the inner surface of the drum 3.

Further, one clock light beam B2 is emitted from the second laser light source 41 toward the galvano mirror 31, and the linear encoder scale 45 of the clock light beam B2 passes through the galvano mirror 31. The reflected light of is detected by the light receiving element 44. Then, a pixel clock signal Sc is generated by the PLL circuit 80 based on the pulse signal corresponding to the amount of the reflected light output from the light receiving element 44, and the modulation timing of the light beam by the multi-AOM 25 is the pixel clock signal. It is determined according to the signal Sc. Therefore, even if the deflection speed (changing speed of the deflection angle) of the galvanometer mirror 31 varies, the modulation timing of the light beam is controlled in accordance with the deflection speed, which causes an error in the exposure position in the main scanning direction. Nothing. As a result, it is possible to improve the image recording accuracy.

Further, in the present embodiment, the second laser light source 41 for generating the clock signal is configured to output a light beam having a wavelength different from that of the laser light source 21 for exposure, Even if the light beam output from the second laser light source 41 is accidentally applied to the photosensitive material 9, the photosensitive material 9 is not sensitized.

In addition, in the image recording apparatus 1 of the present embodiment, as the drum 3, an arc-shaped container in which a cylinder is broken from the height direction is used, but instead of this, a cylindrical container is used. You may comprise. In the case of such a configuration, it is necessary to form the linear encoder scale 45 in an annular shape so that the deflection angle of the optical deflector can be detected over one round around the center axis AX of the drum 3.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to such an embodiment and can be implemented in various modes without departing from the scope of the present invention. Of course, you can.

[0036]

[Effect of device]

 As described above in detail, according to the cylindrical inner surface scanning type image recording apparatus of the present invention, even if the deflection speed by the light deflecting means varies, an error does not occur in the exposure position in the main scanning direction. As a result, it is possible to improve the image recording accuracy.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of an image recording apparatus as an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing the vicinity of an optical deflector of the image recording apparatus.

FIG. 3 shows a first half mirror 33 to a galvano mirror 3
It is explanatory drawing which shows the optical path of the light beam B1 for exposure and the light beam B2 for a clock which reach | attain 1.

FIG. 4 is a schematic configuration diagram showing a control system of the image recording apparatus.

[Explanation of symbols]

 1 Image Recording Device 3 Drum 5 Scanning Mechanism 9 Photosensitive Material 11 Base 13 Reciprocating Mechanism 15 Light Beam Output Section 21 Laser Light Source 22 First Lens 23 Beam Splitter 25 Multi-AOM 25 28, 30 Reflecting Mirror 31 Galvano Mirror 32 First Focusing Lens 33 First half mirror 35 Main scanning motor 41 Second laser light source 42 Second half mirror 43 Second condensing lens 44 Light receiving element 45 Linear encoder scale 45a Slit 45b Reflecting mirror 55 Sub scanning motor 60 Scanning system control Circuit 70 Image processing unit 80 PLL circuit

Front Page Continuation (72) Inventor Koji Nomoto 1 at No. 1 Tenjin Kitamachi 4-chome, Tenjin Kitamachi, Teranouchi, Horikawa-dori, Kamigyo-ku, Kyoto

Claims (1)

[Scope of utility model registration request] 1. A cylindrical inner surface scanning type image recording apparatus for performing image recording by exposing a recording medium held on the inner surface by scanning the inner surface of the cylindrical member with a light beam, wherein an image to be recorded is recorded. First light beam output means for outputting a first light beam modulated accordingly, and a traveling direction of the first light beam from the first light beam output means provided inside the cylindrical member. Light deflecting means for changing the direction toward the inner surface of the cylindrical member; and swinging or rotating the light deflecting means about the central axis of the cylindrical member to generate the first light beam from the light deflecting means. A scanning unit for scanning and exposing the recording medium on the inner surface of the cylindrical member, and a light deflecting unit centered on the central axis of the cylindrical member are provided, and light reflecting portions and light shielding portions are alternately and repeatedly formed. Ring-shaped scale Second light beam output means for irradiating the second light beam toward the scale member via the light deflecting means by outputting the second light beam in the direction of the light deflecting means. A light detecting means for receiving a second light beam reflected by the scale member via the light deflecting means and detecting a change in the light quantity; and a change in the light quantity detected by the light detecting means. And a control unit for controlling the modulation timing of the first light beam of the first light beam output unit based on the above.