JP2008262135A - Image recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image recorder that can reliably carry out APC (auto power control) processing and accurately adjust laser power without inducing interference on a drum surface by a reflected laser beam even when a member which reflects a laser beam such as a drum is arranged at a position facing a laser unit upon adjusting the laser power for APC processing or the like in order to suppress variance in the laser power among a large number of laser units. <P>SOLUTION: A blanking part 5A of a drum 5 is covered with a light diffusing member 40 to form a light diffusing part 5B and to diffuse a laser beam in the light diffusing part 5B, which prevents a laser beam reflected on the surface of the drum 5 from reentering the laser unit. A photodetector 14 detects a monitor beam 12b. A control means 30 receives the monitor beam of the required laser beam to reliably carry out APC processing and to accurately control the laser power. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image recording apparatus for recording an image by winding a plate as a recording medium around a drum and irradiating a laser beam.

  In order to form a printing plate for lithographic printing, an aluminum plate with a surface coated with a sensitizer is wound around the outer periphery and a drum is rotated, and this plate is irradiated with laser light to record an image (exposure) There is a device to do.

  In such an image recording apparatus, recording of an image on an aluminum plate wound on a drum is performed by turning on / off a laser beam and exposing a necessary pattern. On the other hand, the laser head provided for the drum rotating at high speed is moved on the scale of the base to perform sub-scanning.

By the way, in such an image recording apparatus, components such as the scale of the drum and the base are configured so as to reduce the influence on the image quality at the time of image recording, and the irradiation position of the laser beam and the like correspond to the variation. There are some which are corrected (see Patent Document 1).
JP 2002-98925 A

  The conventional image recording apparatus has a configuration with sub-scanning that moves the optical recording head on the scale of the base, but in order to reduce the distance of the sub-scanning movement, the number of laser units incorporated in the optical recording head There is also an increasing trend.

  In recent years, optical recording heads with almost no sub-scanning movement have been developed, and each laser unit can be individually adjusted by APC (auto power control) in order to suppress variations in each laser unit. It can be done.

  However, in APC, there is a problem that the optimum light amount adjustment cannot be performed by the return light (laser light output from the laser unit and reflected on the drum side).

  That is, the APC process is to adjust the laser power by suppressing the decrease in the laser power caused by the environmental temperature, and receives a part of the laser beam output from the laser package of the laser unit. The laser power is adjusted so that becomes a predetermined value.

  As shown in FIG. 12, the laser package 12 includes a photodetector 14 that is a light receiving element that converts the amount of monitor light 12b from a laser chip 12a that is an LD (laser diode) into a PD signal (photodetector signal). From the laser chip 12a, most of the light is emitted as laser light to the glass 15 side. The monitor light 12b is emitted as weak light on the opposite side.

  However, a drum around which a plate, which is a recording medium, is wound is polished like a mirror around the entire circumference in order to wind the plate without unevenness. Accordingly, as shown in FIG. 12, when there is return light B reflected in the blanking portion, assuming that the energy is Pk, the photodetector 14 is the sum of the energy Pm of the monitor light 12b and the energy Pk of the return light B. A current Im proportional to is generated.

Im = b × (Pm + Pk) (b is a constant)
Therefore, there has been a problem that Pk becomes a disturbance factor and accurate APC processing cannot be performed.

  The present invention solves such problems, and its purpose is to perform laser power adjustment such as APC processing for the purpose of suppressing variations in laser power among a large number of laser units. Even when a member such as a drum that reflects laser light is placed at a position facing the unit, there is no interference due to the reflected light of the laser on the drum surface, APC processing can be performed reliably, and laser power is adjusted accurately. It is an object to provide an image recording apparatus capable of performing the above.

  An image recording apparatus of the present invention comprises an optical recording head comprising a drum on which a plate on which an image is recorded is wound and mounted and rotation-controlled, and a laser unit for recording an image on the plate against the drum. An image recording apparatus comprising: a light diffusing means for diffusing a laser beam output from a laser unit so as to be movable to a position facing the laser unit; and receiving a monitor beam of the laser beam to adjust a laser power It has a control means.

  According to the image recording apparatus of the present invention, the laser light output from the laser unit is diffused by the light diffusing means, so that there is no interference due to the reflected light of the laser light on the drum, and the control means The monitor light can be received, the auto power control process can be executed reliably, and the laser power can be adjusted accurately.

  An image recording apparatus according to a first aspect of the present invention includes a drum on which a plate on which an image is recorded is wound and mounted and rotation-controlled, and a laser for recording the image on the plate against the drum. An image recording apparatus comprising an optical recording head comprising a unit, wherein a light diffusing means for diffusing laser light output from the laser unit is provided so as to be movable to a position facing the laser unit and receives monitor light of the laser light Thus, a control means for adjusting the laser power is provided.

  With the above configuration, the laser light output from the laser unit is diffused by the light diffusing means, so that there is no interference due to the reflected light of the laser light on the drum, and the control means receives the necessary monitor light of the laser light. Thus, for example, the auto power control process can be executed reliably, and the laser power can be adjusted accurately.

  The image recording apparatus according to a second aspect of the present invention is the image recording apparatus according to the first aspect, wherein the light diffusing means is provided with a light diffusing member on a blanking portion of the drum surface where the plate is not wound. The light diffusion portion is formed along the axial direction of the drum.

  With the above configuration, the laser light can be diffused by the light diffusion portion. For this reason, there is no interference due to the reflected light of the laser beam on the drum, and the control means can receive the necessary monitor light of the laser beam. For example, the auto power control process can be executed reliably and accurately. The laser power can be adjusted.

  An image recording apparatus according to a third aspect of the present invention is the image recording apparatus according to the first aspect, wherein the optical recording head is a line head including a plurality of laser units, and the light diffusing means is a drum head. A light diffusing portion provided in a blanking portion on the surface where the plate is not wound, and the light diffusing portion is provided along the axial direction of the drum.

  With the above configuration, the laser light can be diffused by the light diffusion portion. For this reason, even if the optical recording head is a line head composed of a plurality of laser units, there is no interference by the reflected light of the laser light on the drum, and the control means receives the necessary monitor light of the laser light. For example, auto power control processing can be executed reliably, and laser power can be adjusted accurately.

  According to a fourth aspect of the present invention, in the image recording apparatus according to the second or third aspect, the control means adjusts the laser power when the optical recording head faces the light diffusing unit. Is.

  With the above configuration, the control unit changes the laser drive current value for operating the laser unit, for example, in accordance with the light diffusing unit, and suppresses a decrease in the laser power caused by the environmental temperature, etc. The laser power can be adjusted by executing an auto power control process.

  According to a fifth aspect of the present invention, in the image recording apparatus according to any one of the second to fourth aspects, the control means detects a rotational position of the drum. Detects the position of the light diffusing unit by obtaining the position signal output from the, and in accordance with this position detection, the laser drive current value for operating the laser unit is changed to change the laser power to a predetermined value. Is to be executed.

  With this configuration, the control means obtains a position signal output from the rotational position detection means for detecting the rotational position of the drum, detects the position of the light diffusing unit, and operates the laser unit in accordance with this position detection. It is possible to adjust the laser power by changing the current value and suppressing the decrease of the laser power caused by the environmental temperature or the like to execute the auto power control process for setting the laser power to a predetermined value.

  According to a sixth aspect of the present invention, in the image recording apparatus according to the second or third aspect, the control means adjusts the laser power only when the optical recording head faces the light diffusing unit. The optical recording head records an image on the plate while maintaining the adjusted laser power.

  With the above configuration, the control means detects the position of the light diffusing unit, and changes the laser drive current value for operating the laser unit in accordance with the position detection, for example, to reduce the laser power caused by the environmental temperature or the like. The laser power is adjusted by executing an auto power control process that suppresses the laser power to a predetermined value, and the optical recording head can record an image on the plate while maintaining the adjusted laser power.

  According to a seventh aspect of the present invention, in the image recording apparatus according to the sixth aspect, the control means obtains the position signal output by the rotational position detecting means for detecting the rotational position of the drum and obtains the light. The position of the diffusing unit is detected, and in accordance with this position detection, an auto power control process for changing the laser drive current value for operating the laser unit to set the laser power to a predetermined value is executed. After completion of the above, a laser driver for driving the laser unit is operated, and an image is recorded on the plate by the optical recording head.

  With the above configuration, the control means obtains a position signal output by the rotational position detection means to detect the position of the light diffusing unit, and changes the laser drive current value for operating the laser unit in accordance with this position detection, Execute the auto power control process to reduce the laser power drop caused by the environmental temperature etc. and make the laser power a predetermined value, and after the auto power control process is finished, operate the laser driver that drives the laser unit, An image can be recorded on the plate by the optical recording head.

  An image recording apparatus according to an eighth aspect of the present invention is the image recording apparatus according to the fifth or seventh aspect, wherein the auto power control process receives a part of the laser beam output from the laser unit. The laser drive current value is corrected so that the amount of received light becomes a predetermined value, and laser light is output based on the laser drive current value. The predetermined value gradually increases with time. Perform tilt correction.

  With the above configuration, the control means receives a part of the laser beam output from the laser unit, corrects the laser drive current value so that the amount of received light becomes a predetermined value, and based on the laser drive current value By outputting laser light, an auto power control process is performed to maintain the laser power at a predetermined value, the laser power is maintained at a predetermined value, and the predetermined value has a slope that gradually increases with time. By performing the correction, the recording density can be made constant.

  An image recording apparatus according to a ninth aspect of the present invention is the image recording apparatus according to the first aspect, wherein the light diffusing means includes a light diffusing member, and the light diffusing member includes the optical recording head and the drum. Are interposed so as to be orthogonal to the traveling direction of the laser beam.

  With the above configuration, the laser light can be diffused by the light diffusing member. For this reason, there is no interference due to the reflected light of the laser beam on the drum, the control means can receive only the necessary monitor light of the laser beam, and the auto power control process can be executed reliably and accurately. The laser power can be adjusted.

  According to a tenth aspect of the present invention, in the image recording apparatus according to the second or third aspect, the control means adjusts the laser power for each of a plurality of rotations of the drum.

  With the above configuration, the control means detects the position of the light diffusing unit for each of a plurality of rotations of the drum, and changes the laser drive current value for operating the laser unit in accordance with the position detection, for example, according to the environmental temperature. It is possible to adjust the laser power by executing an auto power control process that suppresses a decrease in the laser power that occurs and sets the laser power to a predetermined value.

  Embodiments of an image recording apparatus according to the present invention will be described below with reference to the drawings.

  1 is a perspective view of an image recording apparatus according to the present invention, FIG. 2 is a perspective view of a light diffusing member, FIG. 3 is a perspective view of a drum, and FIG. 4 is a perspective view of a unit main body of an optical recording head according to the present invention. 5 is a front view of the unit main body, FIG. 6 is an explanatory view showing the arrangement of laser units provided in the unit main body, FIG. 7 is a front view of a state in which a plurality of the unit main bodies are arranged, and FIG. FIG. 9 is an enlarged sectional view taken along the line DD of FIG. 8, and FIG. 10 is an explanatory view of the positional relationship between the head main body and the drum.

  As shown in FIG. 1, an image recording apparatus G according to the present invention includes a drum 5 around which a sheet-like plate 4 (aluminum plate) that is a recording medium is wound, and an optical recording head H. The drum 5 performs main scanning. The optical recording head H is rotated in the sub-scanning direction Y orthogonal to the main scanning direction X by the linear motor 7 (see FIG. 13), which is rotated in the main scanning direction X by the servo motor 6 as control means. It is designed to reciprocate. In addition, an encoder 70 serving as a rotation position detecting means for detecting the rotation position of the drum 5 is connected to the rotation shaft of the servo motor 6.

  Further, the drum 5 is polished like a mirror over the entire circumference in order to wind the plate 4 without unevenness. As shown in FIG. 1, the drum 5 is blanked even when the plate 4 is wound. There is a remaining portion as the portion 5A. This blanking portion 5A is provided with a light diffusing member 50 as a light diffusing means, and constitutes a light diffusing portion 5B.

  That is, as shown in FIG. 2, the light diffusing member 50 includes a member main body 50 </ b> A, and this member main body 50 </ b> A has a long strip shape in the sub-scanning direction Y that is the axial direction of the drum 5. The length dimension is made equal to the length dimension of the blank king portion 5A, and its surface is blasted so that light is diffused. A plurality of attachment pieces 51 are provided at both side edges of the member main body 50 </ b> A at intervals in the sub-scanning direction Y, and attachment holes 52 are provided in these attachment pieces 51. The light diffusing member 50 is fixed to the drum 5 with a screw member (not shown) at the mounting piece 51, and the light diffusing member 50 covers the blanking portion 5A.

  As will be described later, the return light B (see FIG. 12) reflected by the blanking portion 5A affects the PD value detected by the photo director 14 described later. Therefore, the blanking portion 5A is covered with the light diffusing member 50 in order to prevent the reflection of the laser beam 12b reaching the blanking portion 5A.

  As shown in FIG. 4, the optical recording head H includes a unit main body 1, and the unit main body 1 has a recording magazine 3 in which a large number of laser units 2 are provided. In the recording magazine 3, as shown in FIG. 5, a plurality of laser units 2 are arranged in a row L parallel to the sub-scanning direction Y, and, for example, five stages L1 to L5 are provided in the main scanning direction X. That is, the optical recording head H is a line head composed of a plurality of laser units 2.

  Then, as shown in FIG. 6, the laser units 2 arranged in each row L are shifted in the sub-scanning direction Y for each row L1 to L5. That is, if the laser unit 2 at the end of L1 in the first row is the recording laser channel ch1, the recording laser channel ch2 is arranged in the second row L2, and the pitch between the recording laser channel ch1 and the recording laser channel ch2 is the inter-laser pitch. (Μm). Thereafter, the recording laser channel ch6 is provided in the first column L1 by shifting the recording laser channel ch3, the recording laser channel ch4, and the recording laser channel ch5 by the inter-laser pitch for each column L1 to L5.

  As a result, the adjacent pitch (actual arrangement pitch) of the laser units 2 arranged in the first row L1 is almost five times that in the case where the laser units 2 are arranged in the same row, so that the cases 2a (see FIG. 9) of the laser units 2 The recording magazines 3 can be arranged without interfering with each other. As shown in FIG. 7, in the optical recording head, the unit main body 1 is connected in a plurality of units U1, U2... Un and the sub-scanning direction Y in order to record a high resolution image on the plate 4 at high speed. Are used.

  As shown in FIG. 9, the laser unit 2 has a laser package 12 provided in a cylindrical case 2a and an optical system 13 that irradiates the plate 4 with a laser beam 12c emitted from the laser package 12. Yes. The optical system 13 includes a collimating lens 9, a molded lens 10, an aperture 11, and an objective lens 18 arranged in this order on the case 2a in the laser beam traveling direction. In this case, the aperture 11 makes the diameter of the laser beam 12c molded by the molded lens 10 constant.

  As shown in FIG. 9, the laser unit 2 configured as described above is accommodated in the laser unit accommodating portion 15 provided in the recording magazine 3 together with the pressing biasing spring 16. The biasing spring 16 is pressed against the two reference surfaces 17 of the laser unit housing portion 15.

  FIG. 10 shows the positional relationship between the unit main body 1 mounted on the image forming apparatus and the drum 5. For example, the middle stage of the laser units 2 provided in five stages, that is, the laser units 2 in the third row L3. When the center and the center line of the drum 5 are aligned and the focal point 12d of the laser beam 12c of the laser unit 2 in the third row L3 is aligned with the surface of the plate 4 wound around the drum 5, the laser in the third row L3 The shift amount S between the focal point 12d of the laser beam 12c of the laser unit 2 in the fourth row L4 and the second row L2 positioned above and below the unit 2 and the focal point 12d of the laser beam 12c of the laser unit 2 in the third row L3 is When the radius R of the drum 5 is 200 mm, it becomes 0.25 mm, and defocusing occurs between the laser units 2 in the third row L3 and the laser units 2 in other rows. Mau.

  In order to correct this, the laser unit 2 is moved in the contact / separation direction of the plate 4 so that the focus of each laser unit 2 is adjusted so that the laser beam 12c is focused on the plate 4 on the surface of the drum 5. Has been done. When the focus adjustment of all the laser units 2 is completed, each laser unit 2 is fixed to the recording magazine 3 by means of adhesion or the like so that the adjustment position does not shift.

  As shown in FIG. 11, the laser package 12 is a light receiving element that photoelectrically converts the amount of monitor light 12b from a laser chip 12a that is an LD (laser diode) into a PD signal (photodetector signal) that is a detection current. A photodetector 14 is provided, and most of the light is emitted as laser light from the laser chip 12a to the glass 15 side, but monitor light 12b emitted as weak light is received on the opposite side.

  In this case, assuming that the energy of the laser beam is Pp and the energy of the monitor light 12b is Pm, the relationship is directly proportional as shown in the following equation (where a and b are predetermined constants). ).

Pm = a × Pp
The photodetector 14 generates a current Im proportional to the monitor light 12b.

Im = b × Pm = (a × b) × Pp
If the constant of the part (a × b) is obtained in advance with a power meter (not shown), the APC process described later can be executed.

  As shown in FIG. 13, the image recording control means 20 includes an interface unit 23 connected via an interface to an image server 22 on the host system side, a system control unit 24 that receives control signals from the interface unit 23, and a system When a control signal from the control unit 24 is received, a mechanism control unit 25 that controls the sub-scanning control unit 7 that is a feed motor control and a main scanning control unit 6 that is a drum control, and a memory that stores image data from the interface unit 23 (Page memory or line memory) 26 and a signal selector 27 that reads out image data from the memory (page memory or line memory) 26 and selects the laser unit 2 for each line of the image.

  Next, the operation of the image recording apparatus will be described with reference to FIGS.

  The plate 4 on which an image is formed (recorded) by the optical recording head H is mainly used for a printing original plate for printing a printed matter such as a newspaper, and is a sheet-like plate (aluminum coated with a sensitizer or sublimation dye on the surface). (Plate) 4 is wound around the surface of the drum 5 and an image is formed on the plate 4 by the laser beam 12c.

  In forming an image on the plate 4, the image data is stored in the memory (page memory or line memory) 26 from the image server 22 via the interface unit 23, and is read from the memory (page memory or line memory) 26. The output image data is output by selecting the laser unit 2 for each line of the image by the signal selector 27. At the same time, when the image resolution is input from the interface unit 23 and the operation is started, the drum 5 is rotated in the main scanning direction X by the main scanning control means (servo motor) 6 whose rotation is controlled by the mechanism control unit 25. The optical recording head H constituted by a plurality of units U1, U2... Un is reciprocated in the sub-scanning direction Y by sub-scanning control means (linear motor) 7 whose feed rate is controlled by the mechanism control unit 25. Is done.

  The laser unit 2 generates a laser beam 12c corresponding to the image signal. That is, the laser light emitted from the laser chip 12a becomes a laser beam 12c by the optical system 13 and is condensed on the surface of the plate 4, and an image is formed on the plate 4 as follows based on the image data. The

  For example, the sublimation dye applied to the surface of the plate 4 is separated from the plate 4 by the thermal energy of the laser beam 12c, and the discrete sublimation dye is sucked by suction means (not shown).

  While the drum 5 rotates once and moves the plate 4 in the main scanning direction X, the sub-scanning control means 7 moves the unit body 1 in the sub-scanning direction Y of the plate 4 by a predetermined amount, and this operation is repeated. By scanning the entire 4, an image is formed on the plate 4.

  The image formed on the plate 4 is read from the memory (page memory or line memory) 26 and distributed to each laser unit 2 by the signal selector 27. When recording on the plate 4, a laser beam 12 c is irradiated from the laser unit 2 toward the plate 4, but the laser beam 12 c is always controlled to be irradiated at the same position in the main scanning direction X. That is, the next column L2 is irradiated with a delay for a preset time with respect to the column L1 to be recorded first, and the subsequent column L3 is also irradiated with a delay from the first columns L1 and L2 by the set time. The

  A printing original plate is manufactured by forming an image on the entire plate 4 as described above, and a high-resolution image is recorded at a high speed on a printing original plate having a large width.

  Next, the principle of APC will be described.

  FIG. 14 shows the relationship between the laser power P and the laser drive current signal (LD signal) I. Even when the laser is caused to emit light by a constant laser drive current signal (LD signal) I, the temperature (20 ° C. , 40 ° C., 60 ° C.), the laser power P varies. The APC process is a process for changing the laser drive current signal (LD signal) I to set the laser power P to a predetermined value in order to prevent the laser power P from being lowered due to the environmental temperature or the like.

  The system control unit 24 of the image recording control means 20 described above is provided with a control circuit 30 which is a control means shown in FIG. The control circuit 30 includes a detection unit 31 and a control unit 32.

  The detection unit 31 converts the light amount of the monitor light 12b from the laser chip 12a of the laser unit 2 into a current value, and converts the PD signal that is the detection current from the photodetector 14 into a voltage value to detect a detected PD value. An amplifier 33 that outputs (detection photodetector value PD_value) is provided.

  As shown in FIG. 16, the control unit 32 is a microcomputer, and includes an input device 40, an output device 41, a storage device 42, an arithmetic device 43, and a control device 44. The input device 40 includes an AD converter 35 that inputs a detected PD value that is an analog signal detected by the detecting unit 31 and converts the detected PD value into a detected digital PD value (PD_a). The output device 41 includes a digital signal. A DA converter 36 that converts the new LD value (new laser drive value (LD_b)) to an analog signal and outputs the laser drive current value (LD_set) to the laser driver 37 is provided.

  The storage device 42 also corrects the LD value relative to the difference between the target (predetermined) PD value (PD_target), the previous laser drive value (previous LD value (LD_a)), and the target PD value and the detected digital PD value. (Constant obtained during adjustment in advance) β, environmental temperature (environment temperature of the photodetector 14) (Temp_val), overcurrent error threshold (LD_Error), and target PD value slope coefficient α (change in recording density with respect to environmental temperature The inclination coefficient for correction is stored in advance (coefficient obtained at the time of adjustment). Since it has been experimentally shown that the change in recording density with respect to the environmental temperature increases as the environmental temperature decreases, the slope coefficient α is set higher as the environmental temperature is lower.

  In addition, the arithmetic unit 43 calculates a difference Δ between the detected digital PD value (PD_a) and the target PD value (PD_target) to which the temperature inclination is corrected, and multiplies the difference Δ by the ratio β to obtain the laser drive obtained last time. A calculation for obtaining a new LD value (LD_b) by adding the value (LD_a), a determination for determining whether or not the obtained new LD value (LD_b) is equal to or less than a threshold value (LD_Error) of an overcurrent error, and the like are performed.

  In addition, the control device 44 stores the above-mentioned items (target PD value (DP_target), previous laser drive value (LD_a), ratio β, coefficient α, environmental temperature (environment temperature of the photodetector 14) stored in the storage device 42. ) (Temp_val) and overcurrent error threshold (LD_Error)), take out the command, change it into a control signal and transmit it to the output device 41 and the arithmetic unit 43, and operate these devices 40, 41, 42, 43 Then, an APC processing flow described later is executed.

  In the control circuit 30, the DA converter 36 inputs the laser drive current value (LD_set) to the laser driver 37, so that the laser driver 37 causes the laser chip 12 a of the laser package 12 constituting the laser unit 2 to emit light. On the other hand, the detected PD value (PD_value) is read by the photo detector 14 and this detected PD value (PD_value) is input to the AD converter 35. Based on the detected digital PD value (PD_a), the DA converter 36 is updated as described later. A laser drive current value (LD_set) based on the LD value (LD_b) is output.

  The laser drive current value (LD_set) based on the new LD value (LD_b) is input to the laser driver 37, the laser driver current signal (LD signal) is output to the laser chip 12a, and the laser chip 12a emits light. To do. The drive of the laser driver 37 is controlled by a laser signal (LD ON), and the laser unit 2 operates (emits light) during a period in which the laser driver 37 is driven, and a recording laser signal PIX is output to perform recording. Record on the line.

  Next, the relationship among the recording density, the detected digital PD value (PD_a), and the laser drive current value (LD_set) will be described with reference to FIGS.

  In FIG. 18, a dotted line indicates a target PD value (PD_target) that is a target, and the detected digital PD value (PD_a) through the amplifier 33 and the AD converter 35 is the target PD value (PD_target) detected by the photodetector 14. However, even if the laser drive current value (LD_set) is corrected, if the optical recording head H is moved in the sub-scanning direction Y and recording is performed, the heat generated by the laser unit 2 itself is generated. As a result, the recording density decreases due to an increase in the environmental temperature.

  That is, the photodetector 14 senses the monitor light 12b of the laser chip 12a and detects the PD signal. In principle, the amount of laser emission changes with temperature, so the photodetector 14 also senses this, Although a PD signal incorporating a change in temperature is detected, the recording density is lowered because the recording (writing) characteristic on the plate 4 which is an aluminum plate is also affected by the environmental temperature.

  On the other hand, as shown in FIG. 19, the inclination correction is performed so that the target PD value (PD_target) is set to a preset target PD value (PD_target) so that the target PD value (PD_target) gradually increases with the passage of time according to the environmental temperature. And setting a new LD value based on the detected digital PD value (PD_a), correcting the laser drive current value (LD_set) based on the new LD value, and calculating the detected digital PD value (PD_a) over time. The recording density is kept constant by following the target PD value (PD_target) to which the inclination of the ambient temperature that rises along with the correction is added.

  Next, according to the time chart shown in FIG. 17, the drum encoder Z-phase signal (EncodeZ) indicating that the position of the drum 5 with respect to the laser unit 2 is the blanking portion 5A, the APC laser signal (APC Enable), and the recording A laser signal PIX for use, a laser signal (LD ON), a PD signal as a photodetector value, and an APC (auto power control) processing execution section will be described.

  A drum encoder Z-phase signal (EncodeZ), which is a position signal of the drum 5 output from the encoder 70, is obtained to detect the position of the light diffusion portion 5B of the drum 5. That is, the light diffusion portion 5B appears between the nth rotation and the n + 1th rotation of the drum 5.

  When the position of the light diffusing unit 5B is detected, an APC laser signal (APC Enable) is output in accordance with the light diffusing unit 5B, and the APC process is executed by the microcomputer serving as the control unit 32. When the APC process is completed, recording is performed by outputting a recording laser signal PIX. As shown in FIG. 16, the laser signal (LD ON) is input to the laser driver 37 and controls the driving of the laser driver 37. When the laser unit 2 operates (emits light) during the period in which the laser driver 37 is driven, a detection PD signal output from the photodetector 14 is output.

  Next, the recording flow will be described with reference to FIG.

  When recording is started, the recording line counter is cleared. That is, the count of the line counter is set to “0” (Line cnt = 0) (step ST11). Next, when the laser unit 2 comes to the light diffusing unit 5B, an APC process described later is executed (step ST12).

  When this APC process is completed, for example, the recording process of the first recording line out of 150 lines is performed (step ST13). Then, the recording line counter is incremented (Line cnt = Line cnt + 1) (step ST14), and it is determined whether or not a predetermined number of recording lines have been recorded (step ST15). As a result of the determination, if the specified line has already been recorded, the process ends (step ST16). If the prescribed line is not recorded as a result of the determination, the process returns to step ST12.

  Next, the flow of APC processing will be described with reference to FIG. In the figure, the target PD value (PD_target) is a value set (stored) in the storage device (RAM) 42 of the control unit 32, and the setting is performed in advance at the time of adjustment. LD_a is the previous laser drive value, and the rate β is the rate of correction of the LD value with respect to the difference between the target PD value and the detected digital PD value, and is obtained in advance during adjustment. LD_Error is an overcurrent error threshold.

  First, the APC process is started, and the control device 44 reads the target PD value set in the storage device 42, and the arithmetic device 43 acquires it (step ST21). Next, the computing device 43 reads out the environmental temperature (environment temperature of the photodetector 14) (Temp_val) set in the storage device 42 (step ST22). Next, based on the command from the control device 44, the computing device 43 acquires the slope coefficient α of the target PD value from the storage device 42 based on the environmental temperature (Temp_val) (step ST23).

  Next, the arithmetic unit 43 acquires the detected digital PD value (PD_a) (step ST24). That is, first, the laser driver 37 causes the laser unit 2 to emit light by outputting a predetermined laser drive current value (LD_set) by the DA converter 36 of the output device 41 and inputting it to the laser driver 37. On the other hand, the photodetector 14 reads the PD signal (PD_a), and the PD signal (PD_a) is input to the AD converter 35 of the input device 40 via the amplifier 33 to obtain the detected digital PD value (PD_a).

  Next, the calculation device 43 calculates and obtains a difference Δ between the obtained detected digital PD value (PD_a) and a target PD value (PD_target) to which temperature inclination correction has been performed in accordance with a command from the control device 44 ( Step ST25). That is, the difference Δ = (PD_target + (α × Line_cnt)) − PD_a is calculated.

  Next, the arithmetic unit 43 multiplies the difference Δ by the ratio β (the ratio of correction of the LD value with respect to the difference between the target PD value and the detected digital PD value), and adds the previously obtained LD value (LD_a). Thus, a new LD value (LD_b) is obtained (step ST26). That is, the new LD value (LD_b) = LD_a + Δ × β is calculated.

  Next, the arithmetic unit 43 determines whether or not the obtained new LD value (LD_b) is equal to or greater than an overcurrent error threshold (LD_Error) (step ST27). As a result of the determination, if the new LD value (LD_b) is within the overcurrent error threshold (LD_Error), a laser drive current value (LD_set) for correction is set (step ST28), and the APC process is terminated (step 28). Step ST29).

  If the new LD value (LD_b) exceeds the overcurrent error threshold LD_Error as a result of the determination, an overcurrent error is determined (step ST30), and the APC process is terminated (step ST29).

  Thus, when the laser drive current value (LD_set) is set based on the new LD value (LD_b), this laser drive current value (LD_set) is output from the output device 42 and input to the laser driver 37. The drive of the laser driver 37 is controlled by a laser signal (LD ON), and the laser unit 2 operates (emits light) during a period in which the laser driver 37 is driven, and a recording laser signal PIX is output to perform recording. Make a record on the line. This recording ends when the drum 5 makes one revolution, and the APC process for the next line is executed. For example, the APC process is performed every time 150 lines are recorded.

  Accordingly, as shown in FIG. 19, while the target PD value (PD_target) is recorded on one plate 4 by moving the optical recording head H in the sub-scanning direction Y to a preset target PD value (PD_target). Then, the gradient correction that gradually increases is performed using the gradient coefficient α, and a new LD value (LD # b) based on the detected PD value (PD_value) is set, and based on the new LD value (LD # b) By correcting the laser drive current value (LD_set), the detected digital PD value (PD_a) can be approximated to the target PD value (PD_target) to which the temperature gradient is corrected, and the recording density can be kept constant.

  As described above, according to the embodiment of the image recording apparatus of the present invention, the light diffusing portion 5B can be provided on the drum 5 by covering the blanking portion 5A with the light diffusing member 50. For this reason, the photo director 14 can detect the monitor light 12b without being interfered with the return light B produced by diffusing the laser light and reflecting the laser light by the blanking portion 5A. 30 can receive only the necessary monitor light of the laser beam, can execute the APC process reliably, and can adjust the laser power accurately.

  Further, according to the embodiment of the image recording apparatus according to the present invention, the control unit 30 includes the detection unit 31 and the control unit 32, and the detection unit 31 captures the laser beam as the monitor light, and the monitor light 12b. Is detected by converting the detected light amount into a detected PD value (PD_value) based on the laser drive current value (LD_set), and the control unit 32 determines that the position of the drum 5 output by the encoder 70 relative to the laser unit 2 is blanked. Indicates that it is part 5A. A drum encoder Z-phase signal (EncodeZ) is obtained, and the position of the light diffusing unit 5B of the drum 5 is detected. When the position of the light diffusing unit 5B is detected, an APC laser signal ( APC Enable) is output and APC processing is executed. When the APC process is completed, recording is performed by outputting a recording laser signal PIX. This recording ends when the drum 5 makes one revolution, and the APC process for the next line is executed. For example, the APC process can be performed every time 150 lines are recorded.

  In the embodiment of the present invention described above, the light diffusing member 50 as the light diffusing means is provided in the blanking portion 5A of the drum 5 to constitute the light diffusing portion 5B. However, as shown in FIGS. In the image recording apparatus according to the present invention, the light diffusing member 60 is used as the light diffusing means, and the light diffusing member 60 is interposed between the head body 1 and the drum 5 so as to face the laser beam 12c. You may let them.

  In this case, the return light B does not return to the laser unit 2 side by being diffused by the light diffusing member 60 so that it is reflected by the blanking portion 5A and does not enter the photodetector 14 as return light B. The return light B does not affect the detected PD value detected by the photo director 14. For this reason, the APC process described above can be performed smoothly.

  As a method of interposing the light diffusion member 60 between the head main body 1 and the drum 5 so as to be orthogonal to the laser beam 12c, as shown in FIG. 22, the light diffusion member 60 is orthogonal to the laser beam 12c. It is possible to carry out by linearly moving in the direction of the arrow as shown by an arrow. Also, as shown in FIG. 23, one end of the bending lever 61 is supported at the fulcrum Q and the other end of the bending lever 61 is diffused. This can be done by fixing the upper end of the member 60 and rotating the bending lever 61 around the fulcrum Q.

  In the embodiment of the present invention described above, the control means 30 is configured to adjust the laser power when the optical recording head H faces the light diffusing portion 5B, that is, every rotation of the drum 5. The means 30 may adjust the laser power for each of a plurality of rotations of the drum 5.

  In this case, the control means 30 detects the position of the light diffusing unit 5B for each of a plurality of rotations of the drum 5, changes the laser drive current value for operating the laser unit 2 in accordance with this position detection, and changes the environmental temperature, etc. It is possible to adjust the laser power by executing the APC process for suppressing the decrease in the laser power caused by the above and making the laser power a predetermined value.

  In the image recording apparatus according to the present invention, the laser light output from the laser unit is diffused by the light diffusing means, so that the control means receives only the monitor light of the necessary laser light without interference by the return light. Because it is possible to perform APC processing reliably and adjust the laser power accurately, it is optimal for image recording devices that record images by wrapping a recording medium plate around a drum and irradiating laser light It is.

1 is a perspective view of an image recording apparatus according to the present invention. Perspective view of light diffusing member Perspective view of drum 1 is a perspective view of a unit main body of an optical recording head according to the present invention. Front view of the unit Explanatory drawing showing the arrangement of laser units provided in the unit body Front view with multiple units arranged Side view of the same optical recording head FIG. 8 is an enlarged sectional view taken along the line DD in FIG. Illustration of the positional relationship between the unit body and drum Configuration diagram of the laser package of the laser unit Explanatory drawing when the return light becomes a disturbance in the laser package of the laser unit Block diagram of image recording control means of image recording apparatus according to the present invention Relationship diagram between laser power and laser drive current 1 is a block diagram of an APC control circuit of an image recording apparatus according to the present invention. Time chart in APC processing of the image recording apparatus Relationship diagram between recording density, target PD value and laser drive current value FIG. 7 is a relationship diagram of recording density, target PD value and laser drive current value in the image recording apparatus according to the present invention. Flow chart of recording process APC processing flowchart Explanatory drawing when a light diffusing member is interposed between the head body and the drum so as to be orthogonal to the laser beam Explanatory drawing when a light diffusing member is interposed between the head body and the drum so as to be orthogonal to the laser beam using a bending lever

Explanation of symbols

G Image recording apparatus H Optical recording head 1 Unit body 2 Laser unit 3 Recording magazine 5 Drum 5A Blanking part 5B Light diffusion part 6 Servo motor (main scanning control means)
7 Linear motor (sub-scanning control means)
DESCRIPTION OF SYMBOLS 12 Laser package 12a Laser chip 12b Monitor light 12c Laser beam 13 Optical system 14 Photo detector 20 Image recording control means 22 Image server 23 Interface part 24 System control part 25 Mechanism control part 26 Memory (page memory or line memory)
27 Signal selector 30 Control circuit (control means)
31 Detection Unit 32 Control Unit 33 Amplifier 35 AD Converter 36 DA Converter 37 Laser Driver 40 Input Device 41 Output Device 42 Storage Device 43 Arithmetic Device 44 Control Device 50 Light Diffusing Member (Light Diffusing Unit)
50A member body 51 mounting piece 60 light diffusion member (light diffusion means)
61 Bending lever 70 Encoder (Rotation position detection means)
B Return light LD_set Laser drive current value PD_value Detection PD value PD_a Detection digital PD value LD_b New PD value PD_target Target PD value (predetermined value)

Claims (10)

An image recording apparatus comprising an optical recording head comprising a drum on which a plate on which an image is recorded is wound and which is mounted and rotationally controlled, and a laser unit for recording the image on the plate against the drum. And
A light diffusing means for diffusing the laser light output from the laser unit is provided so as to be movable to a position facing the laser unit, and the monitor light of the laser light is received and the laser power is adjusted in accordance with the received light amount. An image recording apparatus comprising a control unit.   The light diffusing means is a light diffusing portion formed by providing a light diffusing member on a blanking portion of the surface of the drum where the plate is not wound, and the light diffusing portion is along the axial direction of the drum. The image recording apparatus according to claim 1, wherein the image recording apparatus is provided.   The optical recording head is a line head composed of a plurality of the laser units, and the light diffusing means is a light diffusing portion provided in a blanking portion on the surface of the drum where the plate is not wound, The image recording apparatus according to claim 1, wherein the light diffusion portion is provided along an axial direction of the drum.   The image recording apparatus according to claim 2, wherein the control unit adjusts the laser power when the optical recording head faces the light diffusing unit.   The control means obtains a position signal output from a rotational position detecting means for detecting the rotational position of the drum, detects the position of the light diffusing section, and operates the laser unit in accordance with the position detection. The image recording apparatus according to claim 2, wherein an auto power control process for changing the current value to set the laser power to a predetermined value is executed.   The control means adjusts the laser power only when the optical recording head faces the light diffusing section, and the optical recording head records an image on the plate while maintaining the adjusted laser power. The image recording apparatus according to claim 2 or 3.   The control means obtains a position signal output from a rotational position detecting means for detecting the rotational position of the drum, detects the position of the light diffusing section, and operates the laser unit in accordance with the position detection. An auto power control process for changing the current value to set the laser power to a predetermined value is executed, and after the auto power control process is finished, a laser driver for driving the laser unit is operated, and the optical recording head The image recording apparatus according to claim 6, wherein an image is recorded on the plate.   The auto power control process receives a part of the laser beam output from the laser unit, corrects the laser drive current value so that the amount of received light becomes a predetermined value, and based on the laser drive current value The image recording apparatus according to claim 5, wherein the laser beam is output and the inclination correction is performed so that the predetermined value gradually increases as time elapses.   The light diffusing means has a light diffusing member, and the light diffusing member is interposed between the optical recording head and the drum so as to be orthogonal to the traveling direction of the laser light. The image recording apparatus according to claim 1. The image recording apparatus according to claim 2, wherein the control unit adjusts the laser power for each of a plurality of rotations of the drum.

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