JPH03132719A - Simultaneous multi-beam optical modulator - Google Patents

Abstract

PURPOSE:To make the frequency pitches of all voltage-controlled oscillators (VCO) constant by the single-time adjustment of the resistance value of a variable resistance and to improve the operatability by providing an applied voltage voltage varying means which varies voltages applied to the respective voltage- controlled oscillators by adjusting the resistance value of the variable resistor according to the number of interposed fixed resistors. CONSTITUTION:A signal line 50 where image data signals are propagated corre sponding to the number of laser beams split by the AOM 18 is connected to an optical modulating circuit 22. This signal line 50 is connected to the modulators 64 respectively. The resistance value of the variable resistor 78 is adjusted and then a VCO 66 corresponding to light of 8th order is applied with a voltage corresponding to the composite resistance of the variable resistor 78, a reference resistor 74, and one fixed resistor 72 and as the order of output light decreases, the variable resistor 78, reference resistor 74, and fixed resistor 72 are each increased in number by one to apply corresponding VCOs 66 with corresponding voltages.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a laser recording device that divides a laser beam output from a laser into a plurality of parts using an acousto-optic element and simultaneously outputs multiple beams for image recording, etc. The present invention relates to a simultaneous multi-beam optical modulation device used for.

[Prior art]

In a laser recording device, it is necessary to modulate laser light, but it is necessary to modulate a plurality of different pieces of information, such as a voltage controlled oscillator (VC).
One idea is to use one acousto-optic device to simultaneously modulate laser light using the oscillation frequency from O), separate the first-order light of Bragg diffraction into separate pieces of information, and guide them to the recording section. (See Japanese Patent Publication No. 63-5741).

In the configuration described in the above publication, since a plurality of main scans are performed simultaneously, the recording processing time can be shortened.

Here, when enlarging or reducing a recorded image, the output light (
It is necessary to keep the included angle of the primary light, . . . , N-1st order light, Nth order light constant. Therefore, each VCO and this V
A variable resistor is interposed between the power supply voltage applied to CO and the voltage applied to each VC○ is changed by each variable resistor. In this case, if the primary light changes by a predetermined angle, the next secondary light needs to change by an angle equal to the predetermined angle plus the change in the primary light. That is, in the case of N-order light, the angle is changed N times that of the first-order light.

[Problem to be solved by the invention]

However, the above configuration requires as many variable resistors as the number of output lights, and each of them must be operated independently, resulting in poor operability. Furthermore, if each is operated independently, adjustment errors are likely to occur, and the included angle of the output light may not be constant.

Therefore, there is a problem in that the quality of recorded images deteriorates.

In consideration of the above-mentioned facts, the present invention aims to provide a simultaneous multi-beam optical modulator that can change the included angle of output light with a simple operation and perform appropriate angle adjustment.

[Means to solve the problem]

A simultaneous multi-beam optical modulation device according to the present invention includes a plurality of voltage-controlled oscillators whose oscillation frequency changes depending on an applied voltage, and a plurality of carrier waves that are mixed with a predetermined frequency oscillated from the voltage-controlled oscillators to modulate each of the plurality of carrier waves. a plurality of modulation means for obtaining modulation signals, an acousto-optic element to which the plurality of modulation signals from the modulation means are simultaneously applied to split an incident beam into a plurality of beams and simultaneously perform optical modulation, and a number corresponding to the number of voltage-controlled oscillators. a fixed resistor connected in series to the power supply line; and a variable resistor connected in series with the fixed resistor to the power supply line for varying the power supply voltage, and adjusting the resistance value of the variable resistor. Applied voltage changing means for changing the applied voltage to each voltage controlled oscillator according to the number of intervening fixed resistors, thereby keeping the frequency pitch output from each voltage controlled oscillator constant;
have.

[Effect]

According to the present invention, the power supply voltage value is changed by adjusting the variable resistor. Here, the voltage applied to each voltage controlled oscillator differs depending on the number of fixed resistors.

Therefore, the frequency output from each voltage controlled oscillator is controlled so that the frequency pitch of each is constant, rather than changing by a constant amount. That is, by adjusting the resistance value of the variable resistor once, the voltage applied to all the voltage controlled oscillators can be changed by different amounts of change, and the frequency pitch of each can be made constant, improving operability. Further, when an image is recorded using this output light, image quality is not impaired even when an enlarged image or a reduced image is obtained from a standard image.

〔Example〕

FIG. 2 shows a laser beam recording device 10 to which the simultaneous multi-beam optical modulation device of the present invention is applied.

The laser 12 outputs a laser beam in response to an on/off signal from a laser power source 14.
This laser beam is input through a lens 16 to an acousto-optic device (hereinafter referred to as AOM) 18 that constitutes a part of a simultaneous multi-beam optical modulator.

AOMlg is controlled by an AOM driver 20. The AOM driver 20 is connected to an optical modulation circuit 22 which together with the AOMlg constitutes a simultaneous multi-beam optical modulation device. This optical modulation circuit 22 has the role of controlling the AOM driver 20 to change the intensity of optical modulation by the AOMlg, and its configuration will be described later.

In this embodiment, the laser beam output from the AOMlg is divided into eight laser beams (not including the zero-order beam) and is sent to the polygon mirror 2 via the lens 24 and mirror 26.
8 is input. The polygon mirror 28 is configured to be rotated at high speed by a polygon driver 30, and is configured to perform main scanning by reflecting the input laser beam on a reflective surface. The laser beam reflected by the reflective surface of the polygon mirror 28 enters the scanning lens 29, and after exiting from the scanning lens 29, it passes through the mirror 32 and the laser beam 3.
3 and is further input to a galvanometer 36 via a mirror 34. The reflecting surface of the galvanometer 36 is movable in the sub-scanning direction, and moves in the sub-scanning direction every time one main scanning of the laser beam is completed to change the direction of reflection of the laser beam.

The laser beam reflected by the galvanometer 36 reaches a stage 42 via a mirror 38 and a lens 40. A recording material 44 is placed on the stage 42, and the laser beam is irradiated onto the recording material 44, so that an image can be recorded on the recording material 44.

The recording material 44 is wound in layers on reels 46 and 48 at both ends in the longitudinal direction, and when recording of one image is completed, the recording material 44 is wound from one reel 46 to the other reel 48.
This is the configuration that will be moved to.

As shown in FIG. 1, the AOM1 is connected to the optical modulation circuit 22.
A signal line 50 that propagates image data signals corresponding to the number of laser beams divided by 8 is manually operated. The signal lines 50 are each connected to a modulator 64.

Although not shown, the signal lines 50 are branched, one being sent to a delay circuit, and the other recognizing the number of on-state image data signals. Here, by changing the light intensity of the image data signal that is delayed and output by the delay circuit in accordance with the number of recognized image data signal ONs, output fluctuations due to so-called competition for light are prevented.

Note that the delay circuit is set in consideration of the time required to recognize the number of on-states of the image data signal.

These modulators 64 each include a voltage controlled oscillator (V
CO) 66 are connected, and each signal is modulated to a predetermined frequency for division by the AOMI 8. The modulators 64 are each connected to a mixer 68 via an amplifier 67. The mixer 68 mixes the image data signals output from the respective modulators 64 and outputs the AOM.
It is output to the driver 20.

The voltage applied to the VCO 66 is supplied via a power supply line 70. A plurality of fixed resistors 72 having the same resistance value are connected in series to the power supply line 70 (in this embodiment, there are 7 fixed resistors 72).
) are connected. Furthermore, reference resistors 74 and 76 are connected in series to both ends of these fixed resistors 72. Further, a variable resistor 78 is connected to one end of the power supply line 70. A branch line 80 is connected between the reference resistor 74 and the first stage fixed resistor 72, and is connected to the VCO 66 corresponding to the eighth-order light signal. Also, from the first stage to 7
A branch line 80 is connected between the fixed resistors 72 in each stage, and V corresponding to the signals from the seventh-order light to the second-order light, respectively.
Connected to CO66. Further, a branch line 80 is connected between the seventh stage fixed resistor 72 and the reference resistor 74, and is connected to the VCO 66 corresponding to the eighth-order light signal.

Here, when the resistance value of the variable resistor 78 is adjusted, a voltage corresponding to the combined resistance of the variable resistor 78, the reference resistor 74, and one fixed resistor 72 is applied to V6O13 corresponding to the 8th order light. As the order of the output light decreases, the number of fixed resistors 72 combined with the variable resistor 78 and the reference resistor 74 is increased by one to the corresponding VCO 66, and the number of fixed resistors 72 is increased by one. voltage is applied.

The operation of this embodiment will be explained below.

First, the image data signal is input to the delay circuit 52 and output after being delayed for a predetermined time. On the other hand, the number of on-states of the branched image data signal is recognized, and the light intensity of the image data signal output from the delay circuit 52 is controlled according to this number, thereby reducing the light intensity due to so-called competition for light. Fluctuations are prevented.

After the image data signals are modulated by respective modulators 64, they are mixed in a mixer 68 and sent to the AOM driver 20.
Output to. From this AOM driver 20 to AOM18
In synchronization with the output to the laser power source 14, the laser 1
2 is turned on to output a laser beam.

The laser beam output from the laser 12 passes through the lens 16
The laser beam reaches the AOM 18 via the AOM 18, and is divided into a plurality of (eight in this embodiment) laser beams in the sub-scanning direction. The divided laser beam is passed through the lens 24
and reaches the polygon mirror 28 via the mirror 26,
By rotating the polygon mirror 28, the reflection direction is changed and the laser beam is main-scanned.

The laser beam reflected by the reflective surface of the polygon mirror 28 is incident on the galvanometer 36 via mirrors 32 and 34. In the galvanometer 36, its reflecting surface is tilted in the sub-scanning direction for each main scanning of the laser beam. In this embodiment, since eight main scans are performed simultaneously, the tilt angle of the galvanometer 36 in the sub-scanning direction is every nine pitches.

The laser beam reflected by the galvanometer 36 passes through a mirror 38 and a lens 40 to the recording material 4 on the stage 42.
4 and an image is recorded.

Here, when enlarging or reducing an image to be recorded, since eight main scanning lines are being recorded at the same time, it is not possible to obtain a desired image simply by changing the amount of sub-scanning movement. Therefore, in this embodiment, the included angle of the laser beam output from the AOMI 8 is changed by adjusting the resistance value of the variable resistor 78.

When the resistance value of the variable resistor 78 changes, the voltage applied to the VCO 66 corresponding to the eighth primary light is controlled by the combined resistance value of the resistance values of the variable resistor 78 and the reference resistor 74. . Next, the VCO corresponding to the seventh primary light
The voltage applied to the resistor 66 is controlled by a combined resistance value obtained by adding the resistance value of one fixed resistor 72 in addition to the above resistance value. The resistance value of one fixed resistor 72 is further added to the next sixth primary light, and the resistance values of the fixed resistors 72 are added one by one up to the subsequent primary lights.

Therefore, by one operation of the variable resistor 78, the voltage applied to the VC066 that controls the eight output lights can be changed by different values. This amount of change is determined by the fixed resistor 72
Since all have the same resistance value, the frequency pitch output from each VCO 66 is matched, as shown by the solid line in FIG. 3, and the included angle between the output lights can be kept constant (angle θ1 ). Note that the output light indicated by the chain line in FIG. 3 indicates the output direction before the change (angle θ2).

Here, depending on the predetermined angle change, the galvanometer 36
The movement amount of the secondary operation is also changed. As a result, all main scanning lines have the same pitch, and an enlarged or reduced image can be obtained without deteriorating image quality. In addition, since this pitch change only requires one operation of the variable resistor 78,
Work efficiency also improves.

In addition, in this example, the lower level of the voltage is assumed to be constant,
Although the upper level was changed by the variable resistor 78, the fourth
As shown in the figure, by changing both the upper and lower voltage levels using two variable resistors 82, the frequency band can be expanded or reduced based on the output corresponding to the intermediate frequency of the plurality of output lights. , the changing bandwidth can be made smaller, making it easier to fit within the bandwidth of the AOM 18.

〔Effect of the invention〕

As described above, the simultaneous multi-beam optical modulation device according to the present invention has the excellent effect of being able to change the included angle of the output light with a simple operation and to perform appropriate angle adjustment.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the optical modulation circuit, Fig. 2 is a schematic configuration diagram of the laser recording device, Fig. 3 is an explanatory diagram showing changes in the output direction of the output light, and Fig. 4 is a diagram showing the configuration of two variable resistors. FIG. 2 is a schematic configuration diagram of the configuration when used. 1O... Laser beam recording device, 12... Laser, 18... Acousto-optic element, 22... Optical modulation circuit, 64... Modulator.

Claims (1)

[Claims] (1) A plurality of voltage-controlled oscillators whose oscillation frequency changes depending on the applied voltage, and a plurality of modulation means that obtain a plurality of modulation signals by respectively modulating a plurality of carrier waves that are mixed with a predetermined frequency oscillated from the voltage-controlled oscillators. , an acousto-optic element to which a plurality of modulation signals from the modulation means are simultaneously applied to split the incident beam into a plurality of beams and simultaneously perform optical modulation; a fixed resistor and a variable resistor connected in series with the fixed resistor to the power supply line to change the power supply voltage, and by adjusting the resistance value of the variable resistor, the voltage controlled oscillator is connected to each voltage controlled oscillator. applied voltage changing means for changing the applied voltage according to the number of intervening fixed resistors to keep the frequency pitch output from each voltage controlled oscillator constant.