JPH1034866A - Laser plate making apparatus with autofocus function and method for removing disturbance of autofocus-detecting laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly perform an autofocusing function by removing disturbance at the time of plate processing by combining a low output autofocus beam with a high output laser beam, detecting a focus error from a reflected beam on a resin sheet, and focus regulating corresponding to an error amount. SOLUTION: An autofocus (AF) laser beam from a detecting LD 56 of an AF detecting block 16 is arrived at a plate sheet 2 via an AF drive block 14 to process it, reflected, returned via the same route, and returned to an non- polarized beam splitter(NPBS) 58 of the block 16. A part of the beam is reflected on the NPBS 58. A focus error signal and a reference signal are calculated by an astigmatism matrix circuit 44, and sent to a DSP control circuit 40. The circuit 40 calculates a focus error amount, ends a lens position movement signal to a lens driver 20 based on it to energize a moving coil 71, thereby regulating an objective lens 52 at a position of just focusing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser plate making apparatus for producing a printing plate used for gravure printing.

[0002] This application is technically related to "laser plate making apparatus and laser plate making method" (same applicant and same inventor) filed in succession. The purpose of the relationship between the two applications is that the present application is mainly intended to license the technical matters relating to the removal of disturbance mixed in the laser prepress apparatus with an autofocus function and the autofocus return beam,
On the other hand, it is an object of a related application “laser plate making apparatus and laser plate making method” to make the right to a technical matter mainly including a lens position sensor and performing focus servo continuously.

[0003]

[Prior art]

[Laser Plate Making Apparatus] (Outline of Configuration) General items of a laser plate making apparatus to which the present invention is applied will be briefly described. The laser plate making device is also called an electronic gravure system plate making device, and is a device for creating a printing plate (intaglio) used at the time of gravure printing.

Conventionally, in gravure printing, a metal plate sheet made of, for example, copper is used as a printing plate (intaglio) used for printing. (Also referred to as "cells") to form a two-dimensional halftone image plate. In the next printing step, after the printing plate is immersed in the ink reservoir, excess ink is scraped off with a blade-like member called a doctor blade and pressed against the paper surface to complete printing. At present, gravure printing is frequently used because it can easily print hundreds to thousands of sheets.

In such an electronic gravure system plate making apparatus, in recent years, an electronic gravure technique using a resin sheet instead of a metal plate has been put to practical use. This type of plate making machine uses a laser beam for plate making, and a concave (cell) corresponding to the density of an image is formed on a resin sheet.
To form a set. As the resin sheet, for example, a sheet in which a surface layer is coated with a thermoplastic resin such as modified polyester is used.

FIG. 9 is a schematic perspective view of a laser plate making apparatus for making such a resin sheet. In the following description, the rotation direction A or B of the plate cylinder 1 shown in FIG. 9 is referred to as “main scanning direction”, and the extending direction of the rail 22 (that is, the plate cylinder 1).
C or D is defined as the “sub-scanning direction”.
As shown in FIG. 9, the laser plate making apparatus includes a plate cylinder 1 that winds and rotates a resin plate sheet 2, a laser block 21, and a sub-scanning direction driving unit 8 that drives the laser block 21 in a sub-scanning direction. And Laser block 2
Reference numeral 1 includes therein a high-power semiconductor laser, an optical system, an autofocus detection optical system, an objective lens driving system, and the like.
The sub-scanning direction driving unit 8 is provided with the laser block moving motor 2.
4, a rail 22, a ball screw 26, a moving element 27 and the like.

(Operation of the Laser Plate Making Apparatus) The plate cylinder 1 is moved via a pulley 6 connected to a shaft of a plate cylinder rotating motor 7 and a timing belt 5 belted around the shaft of the plate cylinder 1. Drive-coupled to the rotation motor 7 and in the main scanning direction A or B
Rotate. The laser block 21 linearly moves in the sub-scanning direction by the sub-scanning direction driving unit 8. That is, in the sub-scanning direction drive unit 8, the laser block moving motor 24
A ball screw 26 is axially connected to the rotation shaft of the ball screw, and the rotational motion of the ball screw is converted into a linear motion of a moving element 27 screwed to the ball screw. The trajectory of the moving element 27 is precisely defined by the rail 22, and the laser block 21 is disposed on the moving element 27. Accordingly, the laser block 21 moves along the rail 22 in the sub-scanning direction C or D in accordance with the rotational movement of the laser block moving motor 24.
Make a linear motion accurately.

(Plate making operation) In the plate making operation by such a laser plate making apparatus, first, a resin plate sheet 2 is wound around the plate cylinder 1. While the plate cylinder 1 is rotated once in the main scanning direction by the plate cylinder rotating motor 7, a laser is irradiated from the laser block 21 toward the plate sheet 2 at a predetermined pixel (dot) position, and the resin at the irradiated spot is removed. By melting and scattering and sublimation, a concave portion (cell) is formed in the plate sheet 2.

After the plate cylinder 1 makes one revolution to form a recess in the resin sheet 2 over one circumference, the laser block 21 is moved by one pixel in the sub-scanning direction by the sub-scanning direction drive unit 8. Again, while rotating the plate cylinder 1 in the main scanning direction, the laser block 21 irradiates a laser to a predetermined pixel position toward the plate sheet 2 to form a recess in the plate sheet 2 over the entire circumference. Thereafter, this operation is repeated until a predetermined sub-scanning direction is reached, and a set of cells corresponding to the image data is formed over a desired area.

The laser plate making apparatus synchronizes the rotation of the plate cylinder 1 by the plate cylinder rotation motor 7 with the linear movement of the laser block 21 by the laser block moving motor 24 while synchronizing the resin from the laser block 21 with the resin. It is a device that irradiates a plate processing laser beam onto a plate sheet 2 made of a plate and forms a set of concave portions (cells) corresponding to an image to be printed on the plate sheet 2.

[0011]

SUMMARY OF THE INVENTION In such a laser plate making apparatus, the inventors of the present invention used a laser plate making apparatus for focusing a plate processing laser beam emitted from a laser block 21 toward a plate sheet 2. Have been considering introducing an autofocus (AF) function into the camera.

[0012] It has also been found that some problems arise when the introduction of the auto-focus function is specifically considered. One of them was found that the unexpected return disturbance was mixed in the autofocus return beam.

Accordingly, an object of the present invention is to provide a laser plate making apparatus with an autofocus function.

Further, the present invention solves the problem concerning disturbance introduced into the auto-focus return beam, which was extracted when the introduction of the auto-focus function was considered. It is an object of the present invention to provide a laser plate making apparatus and a method for removing disturbance.

[0015]

A laser plate making apparatus with an auto-focus function according to the present invention is a laser plate making apparatus with an auto-focus function for forming cells on a resin sheet by a high-power laser beam, and has a relatively low output. Means for emitting an auto-focusing beam, means for synthesizing the auto-focusing beam into the high-power laser beam, and detecting a focus error amount using reflected light from the resin sheet of the auto-focusing beam. Means for adjusting the focus in accordance with the focus error amount.

Further, a laser plate making apparatus with an auto-focus function according to the present invention is a laser plate making apparatus with an auto-focus function, which uses a high-power laser for plate processing and a laser with a relatively low output for auto-focusing. Means for modulating the drive signal of the autofocus laser at a specific frequency different from the frequency of the disturbance mixed in the autofocus return beam during plate processing, and a signal detected by a return optical system of the autofocus detection laser. Is processed by the band filter of the specific frequency, and further down-converted at the same specific frequency to obtain an autofocus detection signal in which the disturbance is reduced. As the specific frequency, for example, a frequency 455 kHz that is distant from a relatively low frequency of disturbance is used.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the laser plate making apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. The same elements shown in the drawings are denoted by the same reference numerals, and redundant description will be omitted.

In the description of this embodiment, a laser plate making apparatus with an autofocus function developed by the present inventors will be described as a first embodiment. Next, a description will be given of the problems of the autofocus function extracted as a result of trial operation of the laser plate making apparatus in various states, and in the next embodiment, a laser plate making with an improved autofocus function which has solved this problem will be described. The apparatus will be described as a second embodiment.

[Block Diagram of Laser Plate Making Apparatus of First Embodiment] (Configuration) (Relation with FIG. 9) FIG. 1 is a block diagram of a laser plate making apparatus with an autofocus function according to the first embodiment. is there. This laser plate making apparatus is substantially similar in appearance to the laser plate making apparatus shown in FIG. In relation to FIG. 9, each block in FIG. 1 will be described. A plate sheet 2 is wound around a plate cylinder 1. The upper end and the lower end of the plate sheet 1 are locked by the chucking plate 3 of the plate cylinder 1.

The plate cylinder 1 is connected to a plate cylinder rotating motor 7, which is driven to rotate in the main scanning direction.
A main scanning encoder 4 is arranged on the rotation axis of the plate cylinder 1, and sends a rotation angle signal to a chucking plate detection circuit 18 according to the rotation of the plate cylinder 1. The chucking plate detection circuit 18 outputs a chucking plate detection signal representing a period during which the chucking plate 3 passes through the laser beam irradiation area to a DSP (Digital Signal Processor).
It is sent to the control circuit 40. The DSP control circuit 40 is similar to a microcomputer and is a control device capable of processing various digital signals at high speed.

A laser block 21 for emitting a laser beam toward the plate sheet 2 of the plate cylinder 1 is arranged. The laser block 21 includes a laser block moving motor 24.
Is moved linearly in the sub-scanning direction. The laser block 21 is provided with a sub-scanning encoder 23, and sends a sub-scanning direction position signal of the laser block 21 to a microcomputer (CPU) 30. The above is the block element of FIG. 2 related to the element shown in FIG.

(Image Data) The laser plate making apparatus shown in FIG. 1 will be described again. A microcomputer (CPU) 30 for controlling the operation of the entire laser plate making apparatus is provided. The CPU 30 includes a data RAM 32 in which image data to be made is stored, and a non-linear conversion table for determining a laser irradiation time, a laser intensity, and the like for each pixel based on the image data read from the data RAM. Gamma table 34 is connected. In the case of color printing, the image data stored in the data RAM 32 is, for example, digital image data of C (cyan), M (magenta), Y (yellow), and BK (black). Laser plate making equipment is C, M, Y, B
A plate sheet 2 is created for each color of K. The CPU 30
The image data is read from the data RAM 32, converted into laser beam irradiation time and laser beam intensity data by the gamma table 34, and these data are converted to a high-power LD.
APC (laser diode automatic control) circuit 36 is sent.

(Main Scanning Direction Control Related Block) As a block element of the main scanning direction control related, a plate cylinder rotating motor driver (motor driving device) 38 connected to the CPU 30
And the plate cylinder rotation motor 7 connected to the plate cylinder rotation motor driver, the main scanning encoder 4 connected to the axis of the plate cylinder 1, a chucking plate detection circuit 18, and the main scanning encoder. And a DSP control circuit 40 and the like. A plate cylinder rotation pulse is sent from the CPU 30 to the plate cylinder rotation motor driver 38, and the plate cylinder rotation motor driver 38 outputs a main scanning direction rotation signal to the plate cylinder rotation motor 7 to rotate the plate cylinder rotation. The motor 7 is rotated. As the plate cylinder 1 rotates, the rotation angle of the plate cylinder 1 is detected by the main scanning encoder 4, and this angle detection signal is sent to a chucking plate detection circuit 18.

The chucking plate detection circuit 18 sends a chucking plate detection signal indicating a period during which the catching plate 3 passes through the laser beam irradiation area (focal position) to the DSP control circuit 40. At the same time, the main scanning encoder 4 sends an angle signal of the plate cylinder 1 in the main scanning direction to the laser block moving motor driver 42 and the CPU 30.

(Sub-scanning direction control related block) As a block element of the sub-scanning direction control, a laser driver for moving a laser block (motor driving device) 42, a motor 24 for moving a laser block, a sub-scanning encoder 23 and the like are included. Have. The plate cylinder 1 is sent from the CPU 30 to the laser block moving motor driver (motor driving device).
Each time the laser block is rotated, a laser block moving pulse is sent, and the laser block moving motor driver 42 outputs a sub-scanning direction moving signal to the laser block moving motor 24 to move the laser block 21 by one pixel in the sub-scanning direction. I do. The sub-scanning position of the laser block 21 is the ball screw 2
6 is detected by the sub-scanning encoder 23 (see FIG. 1) connected thereto, and a laser block position signal is sent back from the sub-scanning encoder 23 to the CPU 30.

In this laser plate making apparatus, a high-power laser beam for processing the plate sheet 2 and a relatively low-power laser beam for auto-focusing adopted for automatic focusing of the high-power laser beam are used. A laser beam source is used. These two laser beams are AF
It is synthesized in the PBS 55 in the drive block 14.

(Laser block for plate processing) A high-power LDAPC is used as a block element for the laser for plate processing.
It has a (laser diode automatic output control) circuit 36, a plate making LD (laser diode) block 12 in the laser block 21, an AF (auto focus) driving block 14, and the like. The plate processing laser beam emission pulse from the CPU 30 is sent to the high output LDAPC circuit 36, and the laser emission signal from the high output LDAPC circuit 36 is sent to the plate making LD block 12, and the plate making LD block 12
The plate processing high-power laser emitted from the printer passes through the AF drive block 14 and is irradiated toward the plate sheet 2 wound around the plate cylinder 1.

For adjusting the output of the high-power laser beam for plate processing, a PD (photodiode) 54 of an FM (front monitor) for a high-power LD (laser diode) is provided in the plate making LD block 12. A part of the beam is fed back to the high-power LDAPC circuit 36, and the high-power LDAPC circuit 3 adjusts the output of the laser beam to a constant or predetermined value.

(Autofocus Related Block) As a block element related to the autofocus, an AF (autofocus) drive block 14 in the laser block 21 is used.
And an AF (autofocus) detection block 16
, An IV converter 45, and an astigmatism matrix circuit 44
, A DSP control circuit 40, a detection LDAPC (laser diode automatic output control) circuit 46, a high frequency modulation circuit 48, and the like. The autofocus laser beam emitted from the detection LD (laser diode) 56 of the AF detection block 14 reaches the plate sheet 2 wound around the plate cylinder 1 through the AF drive block 14 and is reflected there. To return to the same route, and
Return to the PBS (unpolarized beam splitter) 58.

As an autofocusing beam, a part of the laser beam is reflected by the NPBS 58 and is reflected by the astigmatism matrix circuit 44 by the FE (focus error) signal and the R signal.
F (reference) signals are calculated, and these signals are DS
It is sent to the P control circuit 40. The DSP control circuit 40 calculates a focus error amount based on these signals, and sends a lens position movement signal to the lens drive circuit 20 based on the calculated focus error amount. The lens position drive circuit 20 responds to the lens position movement signal by a moving coil ( MC) 71, and OL
The lens position of the (objective lens) 52 is adjusted to the just focus position. This is the focus servo system of the objective lens.

A PD (photodiode) 59 of a detection LD FM (front monitor) in the AF detection block 16 is provided for adjusting the output intensity of the autofocus laser beam. Is reflected by the NPBS 58, detected by the PD 59, and the detected autofocus beam intensity detection signal is sent to the detection LDAPC circuit 46. LDAP for detection
The C circuit 46 outputs the beam control signal for autofocus,
Sent to the detection LD 56 via the high frequency modulation circuit 48,
The output of the autofocus laser beam emitted from the detection LD 56 is adjusted.

The high-frequency modulation circuit 48 modulates the oscillation signal of the detection LD 56 at, for example, 400 MHz.
This is for suppressing the return light noise of the detection LD 56 which is caused by returning to D56 (return light amount), and is not directly related to the present invention.

(Laser Block) Next, each element in the laser block 21 will be described. Laser block 2
1 is roughly divided into a plate making LD (laser diode) block, an AF (auto focus) driving block 14,
An AF (auto focus) detection block 16. The high-power laser beam for plate processing uses optical elements included in the plate making LD block 12 and the AF drive block 14, and the laser beam for autofocus uses optical elements included in the AF detection block 16 and the AF drive block 14. doing.

(Plate making LD block) Plate making LD block 2
1 is a high-power LD (laser diode) 10 for emitting a high-power laser for processing, and a CL (collimator lens) 50
And an ANM (anamorphic prism) 51 and a PD 54 for a front monitor for a high-power LD.

The high-power LD 10 emits a P-polarized plate-use high-power laser beam for plate processing, and the laser beam enters the CL 50. The high-power LD block 21 is, for example, a high-power semiconductor laser, for example, a near-infrared laser diode, and has a relatively high output of 2 [W] and a wavelength λ of, for example, about 800 [nm], which is currently commercially available. TAPS (taperedstr
ipe) emits a laser beam.

Here, the “P-polarized light” generally includes the direction of vibration of the electric vector incident on the sample surface within the incident surface (the surface including the normal to the sample surface and the wave normal to the traveling direction of the beam). In general, the “S-polarized light” refers to a plane in which the direction of oscillation of the electric vector of light incident on the sample surface includes the incident surface (the normal line of the sample surface and the wavefront normal (the traveling direction of the beam)). ) Is linearly polarized light perpendicular to the direction, and both are orthogonal to each other.

The CL (collimator lens) 50 has a predetermined focal length, and functions to collimate (also referred to as "collimation") the light beam of the laser beam from the high-power LD 10 into light parallel to the optical axis. Optical element.

The laser beam collimated by the CL 50 enters an ANM (anamorphic prism) 51.

An ANM (also referred to as an "anamorphic prism") 51 is an optical element for shaping a beam shape. Therefore, the ANM 51 generates an image having different vertical and horizontal magnifications on an image plane. It is an optical element that works. The ANM 51 has a structure in which, for example, two triangular prisms are combined, and is incident on the inclined side surface of one of the triangular prisms, refracted and emitted from the bottom surface, and incident on the inclined side surface of the other triangular prism. Then, the light is refracted and emitted from the height side surface, and travels toward the PBS 55 in the AF drive block 14.

A part of the beam is reflected by the inclined side surface of the other triangular prism, and is reflected by the PD of the high power LD FM.
The beam intensity is detected by the (photodiode) 54, the detected beam intensity signal is fed back to the high output LDAPC circuit 36, and the beam intensity is controlled so as to have a constant or predetermined beam intensity.

The PBS (polarizing beam splitter) 55 is
It is an optical element that splits into two light beams using a birefringent crystal, and acts so as to transmit incident P-polarized light or reflect incident S-polarized light in the direction of 90 degrees. Therefore, the P-polarized laser beam from the ANM 51 passes through the PBS 55 and
Head to 2.

The OL (objective lens) 52 has a predetermined focal length, and passes the light beam of the P-polarized laser beam from the PBS 55 through the CG (cover glass) 53 to the plate sheet 2 surrounded by the plate cylinder 1. It converges upward to form a predetermined recess (cell) in the plate sheet 2.

(AF Drive Block and AF Detection Block) The AF (auto focus) drive block 14
An MC (driving BS) (polarizing beam splitter) 55, an OL (objective lens) 52, a CG (cover glass) 53, an OL (objective lens) 52, and a CG (cover glass) 53 in the plate direction. (A moving coil) 71.

AF (autofocus) detection block 1
Reference numeral 6 denotes a detection LD (laser diode) 56 that emits an autofocus laser beam, a CL (cover lens) 57, and an NPBS (non-polarization beam splitter) 58.
And an astigmatism optical system DL and ML for processing an autofocus detection beam and a quadrant PD (photodiode)
62, an IV converter 45, and a PD functioning as an FM (front monitor) for a detection LD (laser diode)
(Photodiode) 59. The astigmatism optical system has a DL (composite lens) 60 having a light condensing function and an ML (multi-lens) 61 composed of a cylindrical lens having a beam shaping function. The NPBS (non-polarizing beam splitter) 58 is an optical element that reflects an incident beam from a certain direction at a certain fixed ratio in the direction of 90 degrees regardless of the polarization.

An S-polarized autofocus laser beam having a relatively low output of about 10 [mW] is emitted from the detection LD 56. This laser beam is collimated through the CL 57, passes through the NPBS 58 as it is, and is incident on the PBS 55 in the AF drive block 14. The beam that is S-polarized light is reflected at an angle of 90 degrees, translated (combined) into a high-power laser beam for plate processing, and OL52 and CG53.
To reach the plate sheet 2. After the beam for autofocus detection is reflected by the plate sheet 2, the beam returns to the PBS 55,
The light is reflected at an angle of 90 degrees and travels to the AF detection block 16,
NPBS 58 is reached. The light is reflected by the NPBS 58 at an angle of 90 degrees, is collected by the DL 60, and is then beam-shaped by the ML 61, and reaches the quadrant PD 62.

The quadrant PD 62 may be the same as that used in a method known as an astigmatism method for obtaining a focus error signal in the field of ordinary optical disks. Briefly, the four-segment PD 62 has four light receiving surfaces A, B, C, and D arranged in the upper, lower, left, and right directions. Are incident to form a circular irradiation surface, and the beam is equally and evenly incident on each light receiving surface. Therefore, in the just focus state, the focus error (FE) signal obtained by the following equations (1) and (2) becomes zero. The reference (RF) signal has a predetermined reference value.

FE (focus error signal) = (A + C) − (B + D) (1) RF (reference signal) = A + B + C + D (2)

However, in the underfocus state or the overfocus state, the irradiation surface of the beam has an elliptical shape whose major axis is inclined at an angle of about +45 degrees or about -45 degrees, and the light receiving surfaces A, C or B on the diagonal line. , D, a relatively large beam is incident on the other, and a relatively small beam is incident on the other, so that the focus error (FE) signal takes a positive or negative value, and The reference (RF) signal will also deviate from the predetermined reference value. Therefore, the four-divided PD 62 can detect the just-focused state, the underfocused state, or the overfocused state including the degree thereof.

The signals from the light receiving surfaces A, B, C, and D of the four-divided PD 62 are subjected to current / voltage conversion by the IV converter 45 and sent to the non-aberration matrix circuit 44. The non-aberration matrix circuit 44 calculates the FE signal and the RF signal according to the above equations (1) and (2). The FE signal and the RF signal are sent to the DSP control circuit 40. D
The SP control circuit 40 sends a lens movement pulse to the lens drive circuit 20, moves the OL 52 to adjust the focus so that the FE signal becomes zero and the RF signal becomes a predetermined reference value. The lens drive circuit 20 outputs a lens movement signal corresponding to the lens movement pulse to an MC (moving coil) 71.
To adjust the OL 52 to the just focus position.

(Details of Position Adjustment of Object Lens OL by MC) The focus of the objective lens OL 52 is adjusted by adjusting the distance to the plate sheet 2 wound around the plate cylinder 1. FIG. 2 is a diagram illustrating details of the focus adjustment mechanism. The objective lens OL52 is, for example, P
A cylindrical member made of resin such as BT (polybutylene terephthalate) is fixed to one open end of a bobbin 70. The bobbin 70 is suspended from a housing 75 by a damper (for example, a leaf spring) 72 having elasticity and flexibility. In practice, damper 72 may be a spiral leaf spring extending from housing 75 toward bobbin 70. For this reason, the bobbin 70 stays at the neutral position unless some force due to an external factor is applied.

An MC (moving coil) 71 is wound around the bobbin 70 near the other open end.
The MC (moving coil) 71 is a member having the same principle as a voice coil motor used in the field of a speaker, and is located in a gap of a yoke 74 having a magnet 73 and a substantially C-shaped cross section. . By adopting such a configuration, the distance between the bobbin 70 and the objective lens OL52 is moved toward and away from the plate sheet 2 depending on the direction and magnitude of the current flowing through the MC 71.

(Plate Making Operation of Laser Plate Making Apparatus) Referring again to FIG. 1, the CPU 30 moves the laser block 21 by one pixel in synchronization with the sub-scanning direction in one rotation of the plate cylinder 1. The main scanning direction movement pulse is output to the plate cylinder rotation motor driver 38, and the sub-scanning direction movement pulse is output to the laser block movement motor driver 42, and the plate cylinder rotation motor 7 and the laser block movement motor, respectively. The motor 24 is driven to rotate, and the laser block 21 is synchronously moved with respect to the plate cylinder 1 in the sub-scanning direction each time the plate cylinder 1 completes one rotation.

The CPU 30 sequentially reads out the image data stored in the data RAM 32, compares it with the gamma table 34, and places a concave portion (cell) having a shape corresponding to the read image data on the plate sheet 2. The values of the laser intensity and the emission time required for the formation are determined. The laser intensity data and the emission time data are sent to the high output LDAPC circuit 36, and the high output LD 10 emits light.

The high-power laser beam for plate processing is provided by a CPU.
According to the pulse from 30, the high-power LDAPC circuit 36 drives the high-power LD 10, and the high-power LD emits a high-power laser beam for plate processing. The laser beam is sequentially CL50, ANM51, PBS55, OL52, C
After passing through G53, it is converged on the plate sheet 2 to form a concave portion in the plate sheet 2. The output of the high-power laser beam for plate processing is adjusted by feeding back a detection signal from the PD 54, which is a high-power LD FM, to the high-power LDAPC circuit 36.

On the other hand, the laser beam for auto-focus is emitted from the LD 56 for detection, and this laser beam is sequentially transmitted to the CL 57, the NPBS 58, the PBS 55, and the OL.
CG53, OL52, PBS55, NP
The light reaches the BS 55 and the NPBS 58, where the light is reflected at an angle of 90 degrees, passes through the DL 60 and the ML 61, and reaches the quadrant PD 62. The astigmatism matrix circuit 44 generates the FE signal and the RF signal by the signal of the four-divided PD 62 and outputs
It is sent to the PP control circuit 40. The control amount of the auto focus of the OL 52 is calculated by the DSP control circuit, and the control amount is sent to the lens driving circuit 20, and the lens driving circuit 20 moves the OL 52 by the MC 71. Thus, the focus servo function is performed so that the high-power laser beam for processing is brought into a just-focus state with respect to the plate sheet 2. The output of the autofocus laser beam is adjusted by feeding back a detection signal from the PD 59, which is the detection LD FM, to the detection LDAPC circuit 46.

(ON / OFF control of auto focus when passing through chucking plate) Using FIG. 3, ON / O of auto focus function when passing through the chucking plate
The FF control will be described. The printing sheet 2 is wound around the printing drum 1, and its upper and lower ends are locked by a chucking plate 3. The objective lens 5 is placed at a position opposing the plate sheet 2 and the cover glass CG53.
There are two. The chucking plate 3 has a shape protruding radially from the plate sheet 2 on the peripheral surface of the plate cylinder 1. Therefore, if the auto-focus function is activated even when passing through the chucking plate, the position control range of the objective lens 52 will be out of range. For this reason, it is necessary to turn off the autofocus servo while the chucking plate 3 passes through the laser beam irradiation position (focal position).

FIG. 3A is a diagram showing the position of the objective lens 52 in a stationary state. The objective lens 52 is at a neutral position determined by the damper 72.

FIG. 3B shows a state in which the plate cylinder 1 has started to rotate and the plate making operation has started. During the plate making operation, the above-described auto focus function operates, and the high-power laser beam for processing is maintained on the plate sheet 2 in the just-focused state.

FIG. 3C shows a state in which the plate receiving state is poor and the plate sheet 2 is lifted from the plate cylinder 1. Even in such a state, the auto focus servo operates and the just focus state is maintained.

FIG. 3D also shows that the plate receiving state is poor and the plate sheet 2 is lifted from the plate cylinder 1. Even in such a state, the auto focus servo operates and the just focus state is maintained. Even if the plate cylinder 1 is eccentric, the just-focused state is maintained similarly. Further FIG.
D is immediately before the chucking plate 3 enters the laser beam irradiation position (focus position). At this point, plate cylinder 1
Plate detection circuit 1 by an angle signal from a main scanning encoder 4 (see FIGS. 1 and 2) connected to
8 detects the start of passage of the chucking plate 3, and
A chucking plate detection signal is sent to the P control circuit 40. The DSP control circuit 40 stops sending the lens position drive signal to the lens drive circuit 20. That is, the auto focus function is stopped.

FIG. 3E shows the objective lens 5 suspended by the damper 72 because the autofocus servo is stopped.
2 returns (moves) to a neutral position determined by the damper 72 while performing damped vibration.

Returning to the state of FIG. 3B, the chucking plate detection circuit 18 terminates the passage of the chucking plate 3 by the angle signal from the main scanning encoder 4 (see FIGS. 1 and 2) connected to the plate cylinder 1. Detects and sends a chucking plate detection signal to the DSP control circuit 40.
In the embodiment, this chucking plate passage period is about 3 hours.
0 [msec], which is very short. The DSP control circuit 40
The transmission of the lens position drive signal to the lens drive circuit 20 is started. That is, the autofocus function is restarted. Thereafter, every one rotation of the plate cylinder 1, FIGS. 3B to 3E
Is repeated.

(Effects of the Embodiment) According to the laser plate making apparatus described above, the plate processing is always performed without being affected by the eccentricity of the plate cylinder 1 and the improper printing state (floating of the plate sheet, dust on the back of the plate sheet). The high-power laser beam for use can maintain the focus state just on the plate sheet 2. That is, the PBS 55, OL 52, CG through which the high-power laser beam for plate processing passes.
In the section 53, the laser beam for autofocusing by the autofocus detection optical system is simultaneously translated and passed, the focus state is sensed by the autofocus beam, and the position of the OL 52 is adjusted to maintain the just focus state.

In this way, the high-power laser beam forms an image on the plate sheet 2 without fail, and even if there is an improper plate state due to eccentricity of the plate cylinder 1, floating of the plate sheet, dust on the back of the plate sheet, or the like. Without being affected by this, it is possible to form a stable concave portion while maintaining the just focus state on the plate sheet 2.

[Problems of the First Embodiment] When the laser plate making apparatus of the first embodiment described above was used for various types of plate making, it was found that there could be some problems.

(Interference of Auto Focus Detection Beam) Refer again to the block diagram of the laser plate making apparatus shown in FIG. The plate processing laser beam output from the high-power laser diode 10 is converged on the plate sheet 2 via the polarizing beam splitter 55, the objective lens 52, and the cover lens 53. On the other hand, the detection laser diode 56
Is focused and reflected on the plate sheet 2 via the polarizing beam splitter 55, the objective lens 52, and the cover lens 53, and reflected.
Go back the same route.

Therefore, the plate-forming laser beam and the auto-focusing laser beam are separated by the polarization beam splitter 55.
In the section from to the plate sheet 2, the light passes through the same optical element and is focused on a position very close to the plate sheet 2. Here, each optical element is non-reflective (N
R) The coating process is applied to minimize the effects of reflection. However, while the high-power laser for plate processing has an output of about 2 [W] after the objective lens, the laser for auto-focus detection has an output of about 10 [mW]. It is a relatively very low value of 0.5%. For this reason, even the reflected light of only 1% or less of the high power laser for plate processing may affect the autofocus function.

The two beam focal points on the plate sheet 2 are required to be extremely close to each other in order to sufficiently achieve the autofocus function. The combustion light follows the same path as the autofocus detection beam reflected on the surface of the plate sheet 2 and returns, and eventually enters the four-divided PD 62 and enters as a disturbance (noise) to the detection beam. The autofocus servo function may be disturbed. It is necessary to effectively eliminate such disturbances.

(Loss of Objective Lens Position Control) Please refer to FIG. 3 again. The autofocus start operation after passing through the chucking plate shown in FIG. 3B when returning from FIG. 3E to FIG. 3B is, specifically, an operation of driving the objective lens 52 to the just focus position, that is, a “pull-in operation”. At this time, a detectable range (also referred to as a “pull-in range”) of the defocus distance of the objective lens OL52 (the distance between the focus of the objective lens and the plate surface) is equal to the objective lens OL.
52 and the astigmatism optical system (DL6
0, ML61). In the laser plate making apparatus shown in the first embodiment, the pull-in range is about ± 45 [μ
m]. For example, as shown in FIG. 3E, if the plate sheet 2 floats immediately before the chucking plate, the plate sheet 2 easily exceeds the drawing range. Therefore, if the objective lens OL52 is defocused (out of focus) beyond this pull-in range, the pull-in operation fails and the position control function of the objective lens OL52 is lost.

In the plate making operation, the plate sheet 2 is placed on the plate cylinder 1.
And the end thereof is locked by a chucking plate 3. Immediately before the plate cylinder 1 makes one rotation and the laser block 21 hits the chucking plate 3, the chucking plate detection signal is sent from the main scanning encoder 4 to the DS.
The control signal is sent to the P control circuit 40, and the DSP control circuit 40 sends the control cutoff signal to the lens drive circuit 20 to turn off the auto focus function, and turns on the auto focus function again immediately after the chucking plate 3 passes. Scanning is repeated.

In such a case, if the auto focus is turned off by the chucking plate 3, the objective lens OL5
The control 2 becomes free (free), and the damper (leaf spring) 72 performs a free damping movement from its immediately preceding position toward its neutral position by the action of the damper (leaf spring) 72. The time for passing through the chucking plate 3, that is, the time for turning off the auto focus function is as short as about 30 [msec]. Therefore, while the free damping motion does not converge, that is, during the vibration, the next autofocus function is turned on, and the autofocus operation is restarted. Since the pull-in range of the return optical system for the autofocus distance detection is 90 [μm], for example, when the plate sheet 2 has a poor printing state with respect to the plate cylinder 1 and the plate sheet floats immediately before autofocusing is large ( In the case of FIG. 3E), the amplitude of the vibration of the objective lens during passage of the chucking plate 3 becomes large, and even if the auto focus function is turned on immediately after that, the state is beyond the pull-in range. Can cause problems with not working.

Further, when the parallelism between the plate cylinder 1 and the rails 22 (see FIG. 9) is deviated, or when the plate sheet 2 is improperly attached to the plate cylinder 1, Objective lens O when auto focus function is OFF
Even if the vibration of L52 does not occur, if it is out of the pull-in range, the auto-focus function does not work and the pull-in operation fails. The occurrence of such a situation also needs to be effectively eliminated. An improved laser plate making apparatus that can address the above problems will be described as a second embodiment.

[Laser Plate Making Apparatus According to Second Embodiment] (Configuration of Laser Plate Making Apparatus) FIG. 4 is a block diagram showing the configuration of a laser plate making apparatus according to the second embodiment. This laser plate making apparatus differs from the laser plate making apparatus according to the first embodiment shown in FIG. 1 in the following points.

In order to cope with the above-mentioned problem that disturbance is mixed in the autofocus beam, an IV converter 45 is provided between the four-divided PD 62 which is a return path of the autofocus detection beam and the astigmatism matrix 40. And 455
kHz BPF (band filter) 47 and synchronous detection circuit 4
9 are provided. Also, the detection LDAPC circuits 46 to 400, which are paths for adjusting the autofocus beam intensity,
A 455 kHz modulation circuit is provided between the MHz harmonic modulation circuits 48. The 455 kHz oscillator 46 is connected to the synchronous detection circuit 49 and the harmonic modulation circuit 48.

The output signal from the quadrant PD 62 of the AF detection block 16 is converted into a voltage signal through an IV converter 45, passed through a 455 kHz band-pass filter (BPF) 47 and connected to a 455 kHz oscillator 46. The signal is sent to the astigmatism matrix circuit 40 through the detection circuit 49. Further, a signal sent from the detection LDAPC circuit 46 to the high frequency modulation circuit 48 is modulated through a 455 kHz modulation circuit 44 connected to the 455 kHz oscillator 46 and sent to the high frequency modulation circuit 48.

Further, in order to cope with the above-mentioned problem of the loss of the objective lens position control, a lens position sensor 80 for detecting the position of the objective lens 52 is arranged in the auto focus (AF) drive block 14. The lens position signal detected by the lens position sensor 80 is D
It is sent to the SP control circuit 40.

For other block configurations, see FIG.
Is the same as the laser plate making apparatus described with reference to FIG.

(Operation for Dealing with the Problem of Interference of Disturbance) The present inventors have investigated the characteristics of disturbance caused by reflected light, combustion light and the like mixed in the detection beam for autofocus. The result is shown in FIG. FIG. 8 shows the frequency of the autofocus detection beam (return beam) measured at the location of the quadrant PD 62 (see FIG. 1) on the horizontal axis in units of [Hz].
The return light quantity is shown in the unit [W] on the vertical axis. As shown in FIG. 8, it was found that the frequency of the disturbance component was concentrated on a relatively low frequency of several kHz or less. The light generated by the burning of the plate sheet 2 is DC, and even if it has a certain frequency, the plate sheet 2
Cells have a certain pattern,
It is a certain limited frequency. Therefore, it is necessary to set the detection beam to a relatively high frequency that does not include the low-frequency disturbance component, and further, a beam that can cover the frequency range necessary for the autofocus servo is required.

To reduce the influence of disturbance, specifically,
The detection LD is modulated at a specific frequency (455 kHz in the embodiment) distant from the frequency of the disturbance, and the frequency spectrum of the detection beam for autofocus is moved to a frequency region different from the frequency component of the disturbance, whereby the disturbance of the disturbance is reduced. Means to reduce the effect are provided. This specific frequency is not necessarily limited to 455 kHz,
5 kHz is the frequency used in AM radio,
The frequency of 455 kHz was adopted as the specific frequency because the used parts could be easily obtained at low cost.

Referring to FIG. 4, the laser beam for auto focus detection is collimated by the detection LD 56 into parallel light by the CL 57 by the CL 57, and a part of the beam is converted by the NPBS 58 to the PD 59 of the front monitor (FM) for the detection LD. , And is fed back to the detection LD automatic output control (APC) circuit 46. L for detection
The output from the DAPC circuit 46 is a 455 kHz oscillator 4
The signal is modulated by a 455-kHz modulation circuit 44 connected to 6 (in the actual circuit, it becomes a switching circuit that is turned ON / OFF) and sent to a detection LD 56 via a high-frequency modulation circuit 48 also shown in FIG. Drive. As a result, the autofocus detection signal becomes a 455 kHz carrier modulation signal. However, a harmonic signal by ON / OFF modulation is also included.

After the laser beam for autofocus is reflected on the surface of the plate sheet 2, the CG 53, OL 52, PB
After S55, the light is reflected by the reflecting surface of the NPBS 58, and DL6
After passing through 0 and ML61, it reaches the 4-division PD62. This 4
The output signals A, B, C and D of the divided PD 62 are 455 [kHz
z], the voltage is converted by the IV converter 45, and only the servo band is passed by the 455 kHz BPF circuit 47, and then downconverted to zero frequency by the synchronous detection by the synchronous detection circuit 49. . At this time,
The operation of the 455 kHz BPF circuit 47 eliminates disturbance due to low-frequency reflected light, combustion light, and the like, and thereafter, the synchronous detection circuit 49 performs detection operation similar to the operation known as heterodyne detection in the radio field to return to the original frequency. It is moving.

The detection signals (A, B,
C, D) are used in the astigmatism matrix circuit 40, so that the focus error (FE) in which the influence of disturbance is reduced
It has become possible to obtain a signal and a reference (RF) signal.

(Operation for Dealing with Loss of Objective Lens Position Control) In order to deal with the above-mentioned problem of loss of objective lens position control, an auto focus (AF) drive block 14 is provided.
Inside, a lens position sensor 80 is added.

The details of the lens position sensor 80 will be described with reference to FIG. Compared with FIG. 2, the bobbin 70, the objective lens (OL) 52, the MC (moving coil) 71, the housing, the damper 72, and the magnet 73 shown in FIG. Is substantially the same. That is, for example, PBT (polybutylene terephthalate)
A cylindrical bobbin 70 made of resin as described above is disposed, and an objective lens (OL) 52 is disposed at one of the opening ends. A MC (moving coil) 71 is wound around the left half of the bobbin 70 as viewed in the drawing. Bobbin 70
Is suspended by a damper 72 from the inner periphery of a generally cylindrical housing surrounding it. For this reason, the magnetic flux emitted from the magnet 73 passes through the coil 71 via the yoke 74. The distance between the objective lens 52 and the plate sheet 2 is controlled by moving the bobbin 70 in the X direction according to the direction and magnitude of the current flowing through the coil 71. The position of the objective lens 52 is always detected by the lens position sensor 80.

The lens position sensor 80 is a PSD (position) generally used in the fields of optical disks and cameras.
sensitive detector) What is called a sensor.
As shown in FIG. 7, the PSD sensor is used in combination with a photodiode, and the PSD is a position sensor that can detect which part of a certain direction (X direction) has received light or which part is shielded from light. It is. A position deviation much larger than the position detection (± 45 μm) by the astigmatism method can be detected.

As shown in FIG. 4, the lens position signal from the lens position sensor 80 is sent to the DSP control circuit 40. The DSP control circuit 40 sends a lens movement signal to the lens drive circuit 20, Urges a moving coil (MC) 71 that performs an electromagnet action. The objective lens 52 moves by the action of the moving coil 71. Thus, the objective lens can be held at the lens position detected by the lens position sensor 80 by the DSP control circuit 40.

The method employed in the first embodiment is a method in which the position control of the objective lens 52 is removed (cut) immediately before the passage of the chucking plate 3 and the position control is resumed immediately after the passage. From the viewpoint of the control system, the FE signal is input to the DSP control circuit 40 to perform servo control except when the chucking plate passes, and when the chucking plate passes, the chucking plate detection circuit 18 receives a signal from the main scanning encoder 4. A chucking plate detection signal is sent to the DSP control circuit 40, and the DSP control circuit 40 sends a hold signal to the lens drive circuit 20, and the control of the lens position by the lens drive circuit 20 is cut off to remove the servo system.

In this case, when the position control is released,
Since the objective lens 52 is movably suspended by the damper 72, damping vibration is generated in an attempt to return to the neutral position. The passing time of the chucking plate is actually about 30
[Msec], which is very short, and may be beyond the position controllable range (pull-in range) depending on the state of damping vibration immediately after the restart of the position control.

In the second embodiment, however, the position of the objective lens 52 at that time is detected by the lens position sensor 80 when passing through the chucking plate 3, and the DSP control circuit 40 Can be used. For this reason, the DSP control circuit 40 includes a storage unit (for example, a RAM)
Then, the lens position output of the lens position sensor 80 is stored in the RAM. During the passage of the chucking plate, the DSP control circuit 40 can apply a servo for holding the lens position at the stored “predetermined position” without removing the control of the position of the objective lens 52.
Therefore, the vibration of the objective lens 52 as described above does not occur.

At this time, the “predetermined lens position” for holding the objective lens 52 may be the lens position indicated by the output of the lens position sensor 80 immediately before passing through the chucking plate. Alternatively, it may be the lens position indicated by the output of the lens position sensor 80 immediately after passing the previous chucking plate (ie, at the start of the previous line). In the latter case, the amount of change in the pull-in position immediately after passing the chucking plate in each round is very small (because only one pixel is moved in the sub-scanning direction), and if the lens is held at the previous line start position. , The pull-in operation can be performed reliably. Which lens position to hold is determined by the performance of the laser plate making apparatus in order to ensure continuous and smooth operation of the autofocus function, and is determined through several trials.

In any case, the focus servo by the FE signal is switched to the focus servo by the lens position signal from the lens position sensor 80 without turning off the focus servo control when passing through the chucking plate, and the focus servo control is returned again. Therefore, it is guaranteed that the position of the objective lens 52 is always within the pull-in range. Therefore, focus servo ON / OFF
As a result, the damping vibration does not occur, and the lens position control immediately after passing through the chucking plate is easily and smoothly restarted.

(Autofocus control when passing through the chucking plate) The operation of the autofocus function when passing through the chucking plate will be described with reference to FIG.
FIG. 6 relates to FIG. 3 of the first embodiment. As shown in the figure, the plate sheet 2 is wound around the plate cylinder 1 and its rear end is locked by the chucking plate 3. The objective lens 52 is located at a position opposed to the plate sheet 2 via the cover glass CG53. Unlike FIG. 2, the lens position sensor 80 is provided on the lower damper 72 as described with reference to FIG. 7, so that the objective lens position can always be detected.

FIG. 6A is a diagram showing the position of the objective lens 52 in a stationary state. The objective lens 52 is at a neutral position determined by the damper 72.

FIG. 6B shows a state where the plate cylinder 1 has started to rotate and the plate making operation has started. During the plate making operation, the above-described auto focus function operates, and the high-power laser beam for processing is maintained on the plate sheet 2 in the just-focused state.

FIG. 6C shows a state in which the plate receiving state is poor and the plate sheet 2 is lifted from the plate cylinder 1. Even in such a state, the auto focus function operates, and the just focus state is maintained.

FIG. 6D also shows that the plate receiving state is poor and the plate sheet 2 is lifted from the plate cylinder 1. Further, immediately before the chucking plate 3 enters the laser beam irradiation position (focal position). At this time, the chucking plate detecting circuit 18 causes the chucking plate detection circuit 18 to output the signal from the main scanning encoder 4 (see FIGS. 1 and 2) connected to the plate cylinder 1.
, And sends a chucking plate detection signal to the DSP control circuit 40. DSP control circuit 40
Switches from the lens position drive signal based on the FE signal and the RF signal to the lens position drive signal for driving to the lens position detected by the lens position sensor 80 in response to the chucking plate detection signal. The position of 52 is held at a predetermined value. As described above, the lens position may be, for example, a lens position immediately before passing through the chucking plate or a lens position immediately after passing through the previous chucking plate.

In FIG. 6E, the position of the objective lens 52 is held at a predetermined position, and the damping vibration of the objective lens 52 as described with reference to FIG. 4E of the first embodiment does not occur, and the focus servo still functions. ing.

Returning to the state of FIG. 6B, the chucking plate detecting circuit 18 terminates the passage of the chucking plate 3 by the angle signal from the main scanning encoder 4 (see FIGS. 1 and 2) connected to the plate cylinder 1. Detects and sends a chucking plate detection signal to the DSP control circuit 40.
In response to the chucking plate detection signal, the DSP control circuit 40 switches from the lens position drive signal for driving the lens position detected by the lens position sensor 80 to the lens position drive signal based on the FE signal and the RF signal. Thus, the position of the objective lens 52 is controlled.

(Effects of the Embodiment) According to the laser plate making apparatus of the second embodiment, the reflected light, which is mixed in the autofocus detection beam pointed out in relation to the laser plate making apparatus of the first embodiment, The problem of disturbance caused by combustion light or the like can be effectively eliminated.

[0100]

According to the present invention, a laser plate making apparatus with an autofocus function can be provided.

Further, according to the present invention, the problems that were identified when the introduction of the autofocus function was considered were solved,
It is possible to provide a laser plate making apparatus and a disturbance elimination method in which an autofocus function functions smoothly during plate processing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a laser plate making apparatus according to a first embodiment.

FIG. 2 is a diagram showing details of an autofocus (AF) drive block of the laser plate making apparatus according to the first embodiment shown in FIG.

FIG. 3 shows ON / OFF control of the autofocus function of the laser plate making apparatus according to the first embodiment shown in FIG.
It is a figure explaining over rotation.

FIG. 4 is a block diagram illustrating a configuration of an improved laser plate making apparatus according to a second embodiment.

FIG. 5 is a diagram showing details of an autofocus (AF) drive block of the laser plate making apparatus according to the second embodiment shown in FIG. 4;

FIG. 6 is a diagram for explaining control of an autofocus function of the laser plate making apparatus according to the second embodiment shown in FIG. 4 over one rotation of the plate cylinder.

FIG. 7 is a diagram showing details of a lens position sensor of the laser plate making apparatus according to the second embodiment shown in FIG.

FIG. 8 is a diagram illustrating a frequency of disturbance that may be mixed into a focus detection signal and a frequency shift for eliminating the disturbance in the laser plate making apparatus according to the first embodiment shown in FIG. 1;

FIG. 9 is a diagram illustrating a conventional laser plate making apparatus.

[Explanation of symbols]

1 plate cylinder, 2 plate sheet, 3 chucking plate,
4 main scanning encoder, 5 timing belt, 6 pulley, 7 plate cylinder rotation motor, 8 sub-scanning direction drive unit,
10 light output laser diode (LD), 12 plate making L
D (laser diode) block, 14 AF (autofocus) drive block, 16 AF (autofocus) detection block, 18 chucking plate detection circuit, 20 lens drive circuit, 21 laser block,
22 rail, 23 sub-scanning encoder, 24 laser block moving motor, 26 ball screw, 27 mover, 30 microcomputer (CPU), 32 data random access memory (RAM), 34 gamma table, 36 high output laser diode automatic output Control (LDAPC) circuit, 38 plate cylinder rotation motor driver (motor drive device), 40 DSP (Digital Signal)
Processor) control circuit, 42 laser block moving motor driver (motor driving device), 44 455 kHz
Modulation circuit, 45 IV converter, 46 455 kHz oscillator, 47 455 kHz BPF (band filter) circuit, 48 high frequency modulation circuit (400 MHz), 49 synchronous detection circuit, 50 cover lens (CL), 51 anamorphic prism (ANManamorphic prizm) ), 5
2 Objective lens (OL), 53 cover lens (C
G), 54 Photodiode (PD), 55 Polarization Beam Splitter (PBS Polarization Beam Splitte)
r), 56 detection laser diode (LD), 57 cover lens (CL), 58 non-polarizing beam splitter (NPBS), 59 photodiode (PD), 60
DL (Compound lens doublet), 61 Multi-lens (ML), 62 Quadrant photodiode (PD), 7
0 bobbin, 71MC (Moving Coil moving coil),
72 damper (leaf spring), 73 magnet, 74 yoke, 75 housing, 80 lens position sensor, 8
2 LED, 84 PSD (Position Sensitive Detec)
ter position sensor), 86 light shielding plate, 88 detection circuit,
A, B main scanning direction, C, D sub scanning direction

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shinji Okuda 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Tosumi Fukuoka 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Hideki Kukishima 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Inside (72) Inventor Minoru Horii 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Soniー Inc.

Claims (8)

[Claims] 1. A laser plate making apparatus having an auto-focus function for forming a group of cells on a resin sheet by a high-power laser beam, comprising: means for emitting a relatively low-power auto-focus beam; Means for synthesizing the laser beam with the high-power laser beam, means for detecting a focus error amount using reflected light from the resin sheet of the autofocus beam, and means for adjusting a focus corresponding to the focus error amount. A laser plate making device with an autofocus function, comprising: 2. A laser plate making apparatus with an auto focus function according to claim 1, wherein said means for combining said auto focus beam with said high output laser beam uses a polarizing beam splitter. Plate making equipment. 3. A laser plate making apparatus with an auto focus function according to claim 1, wherein said means for detecting the focus error amount uses an astigmatism method. 4. A laser plate making apparatus having an auto-focus function, which uses a high-power laser for plate processing and a laser for auto-focusing having a relatively low output, wherein a drive signal of the auto-focus laser is automatically transmitted during plate processing. Means for modulating at a specific frequency different from the frequency of the disturbance mixed into the focus return beam; processing a signal detected by the return optical system of the laser for autofocus detection with a bandpass filter of the specific frequency; With means to downconvert
A laser plate making apparatus with an auto focus function, which obtains an auto focus detection signal in which the disturbance is reduced. 5. The laser plate making apparatus with an auto focus function according to claim 4, wherein the means for modulating at the specific frequency is relatively high with respect to a frequency of a disturbance mixed in an auto focus return beam during plate processing. A laser plate making device with an autofocus function that modulates at a specific frequency. 6. The laser plate making apparatus with an auto-focus function according to claim 4, wherein the means for modulating at the specific frequency includes a 455 kHz oscillator, and a 455 kHz high frequency modulation means connected to the 455 kHz oscillator. Laser plate making equipment with auto focus function that modulates the drive signal of the auto focus laser. 7. The laser plate making apparatus with an auto-focus function according to claim 4, wherein said band-pass filter processing at the same specific frequency, and further down-converting at the same specific frequency, comprise a 455-kHz band-pass filter circuit and a 455-kHz oscillator. A laser plate making apparatus having an auto-focus function having a connected synchronous detection circuit. 8. A method for eliminating disturbance of an autofocus detection laser in a laser plate making apparatus using a high-power laser for plate processing and an autofocus laser having a relatively low output, comprising: The signal is modulated at a specific frequency different from the frequency of disturbance mixed into the autofocus return beam during plate processing, and a signal detected by the return optical system of the autofocus detection laser is band-pass filtered at the same specific frequency. Downconverting the band-filtered detection signal at the same specific frequency.