JPH04238317A - Light beam scanner - Google Patents

Abstract

PURPOSE:To provide the light beam scanner with which adequate images are obtainable without generating jitters, etc., by a deviation in synchronization. CONSTITUTION:An AOM 18 splits a laser beam into 8 beams and optically modulates the intensity. The 1st order light of the 8th beam split by the AOM 18 is rotated in polarization angle by 90 deg. by a 1/2lambda plate 80 and is multiplexed with the 1st order light of the 7th beam from the 1st beam by a polarization beam splitter 84; thereafter, this light is separated by a polarization beam splitter 86 and is projected via a linear encoder 40 to a photoelectric converter 60. A control circuit controls the AOM 18 via an AOM driver in such a manner that the respective intensities of the above-mentioned eight laser beams attain prescribed values. A stable synchronizing signal is, therefore, obtd. from the laser beams which do not fluctuate in light quantity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device, and more particularly to a light beam scanning device that performs two-dimensional plane scanning by performing main scanning and sub-scanning of a light beam using a scanning optical system.

0002

[Prior Art] Conventionally, multi-frequency acousto-optic elements (
An optical beam scanning device has been proposed that uses an optical modulation device equipped with an AOM (AOM) to perform stable and high-speed reading or recording with multiple laser beams (Japanese Patent Publication No. 63-574).
Publication No. 1, JP-A-54-5455, JP-A-57-
41618, Japanese Patent Publication No. 53-9856, etc.).

[0003] In such a light beam scanning device, a plurality of signals of different frequencies are input to an acousto-optic element, and the laser beam incident on the acousto-optic element is divided into a plurality of parts.
A scanning optical system consisting of a rotating polygon mirror, a galvano mirror, etc. performs main scanning and sub-scanning of the laser beam, and these multiple laser beams simultaneously irradiate the photosensitive surface to perform two-dimensional plane scanning. Is going.

In the above-mentioned light beam scanning device, in order to keep the main scanning recording position constant, a light beam for forming a synchronizing signal is required in addition to the scanning light beam. By setting the time of input of this synchronization signal or the time when a predetermined time has elapsed since the time of input as the main scanning recording time, it is possible to synchronize each main scanning line.

In order to generate such a synchronization signal, conventionally, in addition to a laser that oscillates a scanning light beam, a laser that oscillates a synchronization signal light beam has been used. In this case, the synchronization signal light beam must be combined before the scanning optical system so that the optical path matches the scanning light beam, and then the synchronization signal light beam must be separated and input to the encoder for synchronization signal generation. There is. Since this combination and separation is performed using a color separation prism (mirror), lasers with different wavelengths are required for the synchronizing signal light beam and the scanning light beam.

However, in the configuration using the above synchronizing signal light beam, it is necessary to install two lasers with different wavelengths, and multiple drive sources are required to drive these lasers, so the number of parts is reduced. There are many problems, and the assembly workability is also poor. In particular, currently, laser recording devices have been developed that can simultaneously perform multiple main scans by dividing a single laser into multiple light beams using an acousto-optic device. It is not preferable to provide another laser to the

[0007] In order to solve the above-mentioned problems, a method has been proposed in which zero-order light passing through an acousto-optic element, which is not used for recording, is used as a synchronization signal.

[0008]

However, the above-mentioned light beam scanning device uses the same light beam inputted to the acousto-optic element by dividing it into a plurality of parts. At this time, the zero-order light of the light beam passing through the acousto-optic element differs when the photosensitive surface is irradiated using multiple light beams at the same time, and when no light beam is used at all and the photosensitive surface is not irradiated. The amount of light fluctuates. If zero-order light, which is not used for recording and has passed through this acousto-optic element, is used as a synchronization signal, the detection level of the detection signal will vary due to variations in the amount of light. For this reason, an appropriate image may not be obtained due to jitter or the like due to synchronization deviation.

SUMMARY OF THE INVENTION In view of the above facts, it is an object of the present invention to provide a light beam scanning device that can obtain a proper image without causing jitter or the like due to synchronization deviation.

0010

Means for Solving the Problems In order to achieve the above object, the invention of claim 1 includes an acousto-optic element that divides an incident light beam into a plurality of beams, and the light beam is scanned by a scanning optical system for main scanning and scanning. A light beam scanning device that performs two-dimensional scanning by performing sub-scanning, comprising synchronization signal generation means for generating a synchronization signal for the two-dimensional scanning using one of the light beams split by the acousto-optic element. It is characterized by:

[0011] The invention according to claim 2 provides an acousto-optic element that divides a light beam into a plurality of parts in a plurality of directions according to the frequency of an input signal and modulates the light to an intensity according to the amplitude of the input signal. A light beam scanning device that performs two-dimensional scanning by performing main scanning and sub-scanning of a light beam using a scanning optical system, the light beam scanning device performing two-dimensional scanning using one of the light beams split by the acousto-optic element. synchronous signal generating means for generating a synchronous signal; and control means for controlling the amplitude of the signal so that the intensity of each of the light beams divided by the acousto-optic element becomes a predetermined value. shall be.

0012

The light beam scanning device according to the first aspect of the present invention performs two-dimensional scanning by performing main scanning and sub-scanning of the light beam using a scanning optical system. Further, the light beam scanning device includes an acousto-optic element that divides the incident light beam into a plurality of beams. The synchronization signal generating means generates a synchronization signal for the two-dimensional scanning using one of the light beams split by the acousto-optic element among the plurality of light beams split by the acousto-optic element. There is.

The light beam scanning device according to the second aspect of the invention performs main scanning and sub-scanning of the light beam by a scanning optical system.
Performs a dimensional scan. Further, the light beam scanning device includes an acousto-optic element that splits the light beam into a plurality of parts in a plurality of directions according to the frequency of the input signal and modulates the light to an intensity according to the amplitude of the input signal. There is. The synchronization signal generating means generates a synchronization signal for the two-dimensional scanning using one of the light beams split by the acousto-optic element among the plurality of light beams split by the acousto-optic element. There is. The control means controls the amplitude of the signal so that the intensity of each of the light beams split by the acousto-optic element becomes a predetermined value.

[0014] Thereby, a stable synchronization signal can be generated using a light beam of a predetermined intensity obtained by the acousto-optic element.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows a laser beam scanning device 10 to which an embodiment of the present invention is applied. This laser beam scanning device 10 is equipped with a base surface plate 62, and on the upper surface of the base surface plate 62, a He
-Ne laser 12 is provided. Instead of this He-Ne laser 12, other gas lasers, semiconductor lasers, etc. may be used. On the laser beam emission side of the He-Ne laser 12, an AOM entrance lens 14 and a reflection mirror 16 are arranged in this order. A laser beam emitted from the He-Ne laser 12 is irradiated onto a reflection mirror 16 via the AOM entrance lens 14, and is reflected by the reflection mirror 16 in the horizontal direction at an angle substantially perpendicular to the optical axis direction.

On the laser beam exit side of the reflection mirror 16, an AOM (acousto-optic modulator) 18, an AOM exit lens 20, a reflection mirror 22, and a relay lens 24 are arranged in this order. AOM18 is AOM driver 72 (Figure 3)
The AOM driver 72 includes a control circuit 7.
4 are connected. This control circuit 74 controls the AOM driver 72 to change the intensity of optical modulation by the AOM 18, and the configuration will be described later. In this embodiment, eight laser beams are used which are modulated by the AOM 18 and emitted as diffracted light.

Furthermore, as shown in FIG. 1, in addition to the eight laser beams mentioned above, the AOM 18 outputs laser beams that are not used for scanning. This laser beam is
This is zero-order light that is not diffracted by the AOM 18 and passes through the AOM 18 in a straight line. The zero-order light that has passed through the AOM 18 is blocked by a light blocking plate 56 disposed on the extension of its optical path. On the other hand, the 8th order light modulated by AOM18 is
The light is incident on the 1/2λ plate 80 arranged on the extension of the optical path. In this 1/2λ plate 80, the polarization plane of the 8th order light is 90°.
be rotated. The 8th order light that has passed through the 1/2λ plate 80 is irradiated onto a polarizing beam splitter 84 via a mirror 82. The polarizing beam splitter 84 is disposed on the optical path of the scanning laser beam emitted from the AOM 18, and as a result, the 8th order light is combined with this scanning laser beam (1st to 7th order light). The light is then irradiated onto the reflecting mirror 22.

The laser beam irradiated onto the reflecting mirror 22 is reflected horizontally at a substantially right angle and irradiated onto the relay lens 24 .

Note that there is a space between the AOM exit lens 20 and the polarizing beam splitter 84 when not recording (for example, when changing the recording from one frame to another, or when changing the recording from one fish to another). AOM
A photoelectric converter 58 is movably mounted so that the laser beam diffracted by the laser beam is incident thereon and the intensity of the laser beam can be monitored.

On the laser beam exit side of the relay lens 24, there are a reflecting mirror 26, a first cylindrical lens 28,
Reflection prisms 30 are arranged in order. The laser beam emitted from the relay lens 24 is reflected by the reflection mirror 26 at a substantially right angle in the vertical direction, and is directed to the reflection prism 3 via the first cylindrical lens 28 for surface tilt correction.
irradiated to 0.

A reflecting mirror 32 and a polygon mirror 34 are arranged in this order on the laser beam exit side of the reflecting prism 30. The reflecting mirror 32 reflects the laser beam emitted from the reflecting prism 30 in a direction forming an angle of approximately 45° with the optical axis so that the laser beam is incident on the polygon mirror 34 . A polygon mirror driver (not shown) that rotates the polygon mirror 34 at high speed is connected to the polygon mirror 34, and the laser beam irradiated from the reflection mirror 32 is
After being deflected by this polygon mirror 34 in the main scanning direction,
Scanning lens 3 placed on the reflective side of polygon mirror 34
6.

A deflection beam splitter 86, a second cylindrical lens 42, and a long mirror 44 are arranged in this order on the laser beam exit side of the scanning lens 36, and a linear encoder 40, on the reflection side of the deflection beam splitter 86.
A photoelectric converter 60 is arranged. The laser beam incident on the second cylindrical lens 42 is a scanning laser beam that linearly passed through the polarizing beam splitter 86, and the eighth-order light
6, it is deflected at right angles. That is, since the polarization plane of the 8th order light is rotated by the 1/2λ plate 80,
It is separated from the scanning laser beam by a polarizing beam splitter 86.

The eighth-order light emitted from the scanning lens 36 is reflected by the polarizing beam splitter 86 and irradiated onto the linear encoder 40. The linear encoder 40 is composed of a flat plate in which a large number of transparent parts and opaque parts are arranged alternately in stripes at a constant pitch in the main scanning direction.
When the top is scanned, the eighth-order light passes through the transparent portion, so that the photoelectric converter 60 outputs a pulse signal. The pulse signal from the photoelectric converter 60 is used as a synchronization signal and is input to a galvano mirror driver (not shown) that controls the angle of the galvano mirror 48. Further, the timing for recording on the photosensitive material 54 is determined using this synchronization signal. On the other hand, the recording laser beam, which is the first to seventh order light that has passed through the polarizing beam splitter 86, is irradiated onto the elongated mirror 44 via the second cylindrical lens 42 for surface tilt correction. The laser beam emitted from the second cylindrical lens 42 is reflected by the elongated mirror 44 in the horizontal direction at an angle substantially perpendicular to the optical axis.

A relay lens 46 and a galvanometer mirror 48 are arranged in this order on the laser beam reflecting side of the elongated mirror 44. The galvano mirror 48 has a reflecting surface that can be moved in the sub-scanning direction by the galvano mirror driver (not shown), and the laser beam emitted from the relay lens 46 is moved in the sub-scanning direction by the galvano mirror 48. reflected in the vertical direction.

On the reflection side of the galvanometer mirror 48, a recording lens 50 attached to a turret 52 and a photosensitive material 54 such as a microfilm are arranged in this order. The laser beam reflected by the galvanometer mirror 48 is directed to the recording lens 5.
The light is irradiated onto the photosensitive material 54 through 0, and an image is recorded on the photosensitive material 54. Both longitudinal ends of this photosensitive material 54 are
Each layer is wound around a reel (not shown), and when exposure of one image is completed, it is moved from one reel to the other reel.

As shown in FIG. 4, the photoelectric converter 60, which is disposed at the above-described position on the laser beam emission side of the AOM 18 and outputs a voltage corresponding to the power of the received laser beam, is an oscillation circuit. (FIG. 3) is connected to a signal generation circuit 70 that outputs a signal for controlling the amplitude of each signal output from the circuit 70 (FIG. 3). The signal generation circuit 70 is A
It is connected to the OM driver 72.

The control circuit 74 includes a register 90 for temporarily storing image data and a data converter 92 connected to the register 90. This image data is given as an 8-bit parallel signal. Note that one of the image data includes a data signal for a synchronization signal. The data converter 92 outputs a 4-bit parallel signal corresponding to the number of turned-on 8-bit signals input from the register 90. A DAC 94 is connected to the data converter 92. The DAC 94 converts the 4-bit parallel signal output from the data converter 92 into an analog signal and outputs it to the AOM driver 72. As shown in FIG. 6, the level of this analog signal increases as the number of ON signals increases. Also, the image data is transferred to the delay circuit 9
After being delayed for a predetermined time in step 6, the signal is input to the AOM driver 72.

As shown in FIG. 3, the AOM driver 72 includes oscillation circuits 62A to 62H, each having a frequency of f1 to f8.
It includes local level control circuits 64A to 64H and switch circuits 66A to 66H. Each of the local level control circuits 64A-64H is connected to each of the output ends of the oscillation circuits 62A-62H, and the local level control circuits 64A-64H
Switch circuits 66A to 66H are connected to the output terminal of 64H, respectively. A double balanced mixer or a pin diode attenuator can be used as the local level control circuit. Further, a signal generation circuit 70 is connected to each of the level control terminals of the local level control circuits 64A to 64H. And the switch circuit 66
Each of the control terminals A to 66H is connected to receive each image data output from the delay circuit 96.

Each output terminal of the switch circuits 66A and 66B is connected to a combiner 68 that mixes two signals at a ratio of 1:1.
They are respectively connected to the input terminals of AB. Similarly, each output terminal of the switch circuits 66C, 66D is connected to the input terminal of the combiner 68CD, each output terminal of the switch circuits 66E, 66F is connected to the input terminal of the combiner 68EF, and each output terminal of the switch circuits 66G, 66H is connected to the input terminal of the combiner 68EF. is combiner 68GH
is connected to the input end of the

The output end of combiner 68AB is connected to amplifier circuit 72AB via total level control circuit 70AB. Similarly, the output terminal of the combiner 68CD is connected to the amplifier circuit 72C via the total level control circuit 70CD.
The output end of combiner 68EF is connected to amplifier circuit 72EF via total level control circuit 70EF, and the output end of combiner GH is connected to amplifier circuit 72GH via total level control circuit 70GH. The output terminals of the amplifier circuits 72AB and 72CD are connected to the input terminal of the combiner 74, and the output terminals of the amplifier circuits 72AB and 72CD are connected to the input terminal of the combiner 74.
Each output terminal of H is connected to an input terminal of combiner 76. The output ends of combiners 74 and 76 are connected to combiner 78, and the output end of combiner 78 is connected to transducer 17. The total level control circuit is composed of a double balanced mixer and a pin diode attenuator like the local level control circuit, and the output terminal of the DAC 94 of the control circuit 74 is connected to each level control terminal.

The operation of this embodiment will be explained below. He-
The laser beam output from the Ne laser 12 is AOM
The light is irradiated onto the AOM 18 via the incident lens 14 and the reflection mirror 16, and is split by the AOM 18 into a plurality of (eight in this embodiment) laser beams in the sub-scanning direction. The split laser beam passes through the AOM exit lens 20, the polarizing beam splitter 84, the reflecting mirror 22, and the relay lens 2.
4 and the polygon mirror 3 via the reflective mirrors 30 and 32.
4, and by the rotation of this polygon mirror 34,
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 passes through the scanning lens 36, the polarizing beam splitter 86, the second cylindrical lens 42, and the elongated mirror 44.
, are incident on the galvanometer mirror 48 via the relay lens 46. The reflecting surface of the galvanometer mirror 48 is tilted in the sub-scanning direction for each main scanning of the laser beam.

The laser beam reflected by the galvanometer mirror 48 is irradiated onto the photosensitive material 54 via the recording lens 50, and an image is recorded.

The data of the image to be recorded is supplied from a host computer (not shown), etc., and the image data is
The signal is supplied to a register 90 and a delay circuit 96. Note that this image data includes data for a synchronization signal. The data converter 92 outputs a digital signal according to the number of ON signals inputted from the register 90, and the DAC 94 outputs an analog signal shown in FIG. 6 according to this digital signal. This analog signal is input to each of the control terminals of total level control circuits 70AB to 70GH. Further, the image data delayed for a predetermined time by the delay circuit 96 is transferred to the switch circuits 66A to 66H of the AOM driver 72.
are input into each of the fields.

After the amplitude of the signals output from each oscillation circuit 62A-62H is adjusted by local level control circuits 64A-64H, the signals are sent to switch circuits 66A-66H, combiners 68AB-68GH, total level control circuits 70AB-70GH, and amplification. AOM1 via circuits 72AB to 72GH, combiners 74, 76, and combiner 78
8 transducers 17. The transducer 17 converts the input signal into an ultrasonic signal according to the frequency and amplitude of the input signal. This ultrasonic signal propagates through the acousto-optic medium 21 and is absorbed by the sound absorber 19 . At this time, when a laser beam is oscillated from the He-Ne laser 12, this laser beam is split by the acousto-optic medium 21 into directions whose intensity corresponds to the amplitude of the ultrasonic signal and whose frequency corresponds to the frequency. The multi-laser beams divided by the AOM 18 are scanned in the main scanning direction by a polygon mirror 28 and scanned in the sub-scanning direction by a galvanometer mirror 36.

FIG. 8 shows the mirror angle of the galvanometer mirror 36 as a function of elapsed time. In a non-recording period before the start of recording of the n-th exposure, image data of the n-th exposure is prepared, the recording material is conveyed for one exposure, and the recording material is positioned. Note that once recording is started, the data of the n-th scan is transferred and the image recording of the n-th scan is performed until the mirror angle of the galvanometer mirror 36 reaches the recording end angle. Also, during the check period of this non-recording period, the photoelectric converter 58 is connected to the AOM.
Amplitude adjustment of signals inserted into the optical path of the laser beam emitted from the oscillator circuits 62A to 62H and output from each oscillation circuit 62A to 62H;
That is, level adjustment is performed.

In this level adjustment, a constant voltage is applied to the level control terminals of the total level control circuits 70AB-70GH, and level adjustment is performed for each oscillation circuit 62A-62H. That is, while the signals are output from the oscillation circuits 62A to 62H, only the switch circuit 66A is turned on. The signal output from the oscillation circuit 62A is supplied to the transducer 17 via a local level control circuit 64A, a switch circuit 66A, a combiner 68AB, a total level control circuit 70AB, an amplifier circuit 72AB, and the like. As a result, from the AOM 18, the oscillation circuit 62
The amplitude of the signal output from A is controlled by the output level of the signal generation circuit 70 input to the local level control circuit 64A, and a laser beam with an intensity corresponding to the amplitude of the output from the local level control circuit 64A is emitted. . AOM1
The laser beam emitted from the photoelectric converter 8 is received by the photoelectric converter 58, and a voltage corresponding to the intensity of the received laser beam is output from the photoelectric converter 58. The signal generation circuit 70 compares the level of the signal input from the photoelectric converter 58 with a preset reference value.

When the level of the input signal is higher than the reference value, the signal generation circuit 70 lowers the voltage applied to the control terminal of the local level control circuit 64A to reduce the amplitude of the signal. When the level of the signal is lower than the reference value, the voltage applied to the control terminal of the local level control circuit 64A is increased to increase the amplitude of the signal. As a result, the intensity of one laser beam emitted from the AOM is adjusted to the target value.

Then, the switch circuits 66B to 66H are sequentially turned on in the same manner as above, and the oscillation circuits 62B, . . .
Level adjustment is performed for 62H, and during this check period, level adjustment is performed for all of the oscillation circuits 62A to 62H individually. During image recording, the signal generation circuit 70
to hold the voltage value adjusted as above.

Furthermore, when recording the data of the nth frame, the register 90, the data converter 92 and the DAC 94
Total level control circuit 70AB, 70CD,
70EF and 70GH are each supplied with an analog signal proportional to the number of image data turns on shown in FIG. 6, and the total level control circuit controls the amplitude of the signals output from combiners 68AB to 68GH according to this analog signal. do. As a result, the intensity of each laser beam output from the AOM 18 becomes constant regardless of the number of ON signals, as shown in FIG. 7, and image density unevenness due to the number of ON signals of image data is prevented. Note that when the amplitude is not controlled by the number of ON signals, the intensity of one laser beam emitted from the AOM will vary as shown in FIG. Change as shown.

Here, in the laser beam recording apparatus 10 of this embodiment, A is used as a synchronization signal that determines the main scanning recording timing.
Eight-order light output from OM18 is used. That is, the 8th order light output from the AOM 18 is first 1/2λ
The plane of polarization is rotated by 90 degrees by plate 80 and then reflected by mirror 82 to polarization beam splitter 84.
is irradiated to. In the polarizing beam splitter 84, the AOM
The scanning laser beam diffracted by the scanning laser beam 18 and the eighth-order light are combined, and as a result, the eighth-order light passes through the same optical path as the scanning laser beam and is output from the scanning lens 36.

The eighth-order light outputted from the scanning lens 36 is deflected in a right angle direction by a polarizing beam splitter 86 and separated from the scanning laser beam. This is because the polarization plane of the 8th order light is rotated by 90 degrees from the polarization plane of the scanning laser beam, and even if the laser beams have the same wavelength, they can be easily separated.

The eighth-order light separated by the polarizing beam splitter 86 passes through the linear encoder 40, and pulsed light is output on the back side thereof. The pulsed light is applied to a photoelectric detector 60, which detects the light and applies it as a synchronization signal. The photoelectric detector 60 converts the input light amount into a current value and outputs it when this current value exceeds a predetermined threshold value, thereby controlling the main scanning recording timing by the scanning laser beam. can.

Furthermore, fluctuations in the intensity of light due to so-called competition for light are prevented, and fluctuations in the intensity of each laser beam are also prevented, so that a constant amount of light can be maintained at all times. Therefore, fluctuations in the amount of light due to main scanning can be reduced, and the S/N ratio of the detection signal can also be improved. Therefore, the synchronization signal is detected at a constant level, and since there is no fluctuation in the detected level, a good image without jitter or the like can be obtained.

In this way, in this embodiment, the polarization direction of the 8th order light output from the AOM 18 is changed and it is applied to create a synchronization signal, so there is no need to separately provide a laser with a different wavelength, and the number of parts can be reduced. be able to. Also, 1
Since the polarization plane of the 8th order light is rotated by 90 degrees with respect to the scanning laser beam using the /2λ plate 80, it is easy to separate the scanning laser beam and the 8th order light by using the polarizing beam splitters 84 and 86. can be synthesized and separated.

In this example, the polarization plane of the 8th order light was rotated by 90° using the 1/2 λ plate 80, but 1/4 λ plates were provided on the incident side and the reflective side of the mirror, respectively, to rotate the circularly polarized light. The plane of polarization may be rotated by 90 degrees after converting once to .

Note that although the light that has passed through the linear encoder 40 is guided directly to the photoelectric converter 60, the light that has passed through the linear encoder 40 is reflected by a mirror and then guided to the photoelectric converter 6.
0, or an acrylic or glass box may be placed in place of the mirror.

In the above embodiment, an example was explained in which a synchronizing signal laser beam is polarized, multiplexed, and separated to obtain a synchronizing signal, but as another embodiment, a synchronizing signal laser beam is polarized. We will explain how to obtain a synchronized signal without combining or separating the signals. In this embodiment, the polarizing beam splitters 84 and 86 are not required. Instead of the polarizing beam splitter 86, a reflecting mirror is provided at a position that reflects only the 8th order light diffracted by the AOM. As a result, A
All of the laser beams diffracted by the OM are deflected by the polygon mirror 34, and only the eighth-order light is irradiated to the reflection mirror and then irradiated to the linear encoder 40. Therefore, the eighth-order light that has passed through the linear encoder 40 is irradiated onto the photoelectric converter 60, and a synchronization signal is obtained. Other controls are the same as in the above embodiment. In this way, it is also possible to detect the synchronization signal without rotating the polarization angle of the synchronization signal laser beam and combining and separating the laser beams using a polarization beam splitter.

As explained above, according to the above embodiment,
When exposing a photosensitive surface with multiple laser beams, the intensity of the laser beams can be kept at a predetermined value even if the characteristics of the acousto-optic elements differ, and fluctuations in the intensity of the light beams over time can be reduced. By preventing changes in the intensity of each beam, the synchronization signal is detected at a constant level, and since there is no fluctuation in the detected level, a good image without jitter etc. can be obtained. It will be done.

[0050] In the above, an example has been described in which the total level control circuit is connected after the combiners 68AB to 68GH that mix two signals.
, 76 or after the combiner 78, a total level control circuit may be connected. In addition, although the example using an acousto-optic element as an optical modulator was explained above,
An optical waveguide type modulator may also be used.

In the above embodiment, an example was explained in which the amplitude of the signal is controlled by the local level control circuit and the total level control circuit to keep the intensity of the laser beam constant. may be controlled to keep the intensity of the laser beam as a synchronization signal constant. Also, in the above example, the switch circuit is turned on and off when adjusting the level of the laser beam.
The laser beam as a synchronizing signal may be always on and only the intensity adjustment may be performed.

In the above embodiment, an example was explained in which a sensor for detecting the intensity of the laser beam was provided on the recording scanning optical path of the laser beam, but a mirror with low transmittance was placed downstream of the AOM, and A sensor may be placed on the back side. In addition, a reflective mirror is installed on the shutter,
A sensor may be provided at a position capable of receiving the reflected light to detect the intensity of the laser beam.

In the above embodiment, an example of a light beam scanning device using a laser beam as the light beam was explained, but a scanning device using LED light as a light beam may also be used, or a scanning device using other light sources may be used. It may also be a light beam.

In the above embodiments, an example was explained in which the intensity of the laser beam is corrected for each frame during non-recording. It may be carried out for each fish, or it may be carried out at a combination of these times.

[0055]

As explained above, since the light beam scanning device according to the present invention uses the diffracted light obtained by the acousto-optic element as a light source for the synchronization signal, each of the obtained diffracted lights has a so-called Fluctuations in light intensity due to competition for light are prevented, and a constant amount of light can be maintained at all times. For this reason,
Fluctuations in light intensity due to main scanning can be reduced, the S/N ratio of the detection signal can also be improved, and furthermore, since there is no fluctuation in the level detected as a synchronization signal, there is no fluctuation in synchronization timing, resulting in improved image quality. can improve
This effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a scanning optical system according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a laser beam scanning device to which the present invention is applied.

FIG. 3 is a block diagram showing an AOM driver according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a control circuit of the AOM.

FIG. 5 is a diagram showing the relationship between the number of image data turns on and the power of a laser beam.

FIG. 6 is a diagram showing the relationship between the number of image data turns on and the level of an analog signal output from a DAC.

FIG. 7 is a diagram showing the relationship between the number of image data turns on and the power of a laser beam.

[Figure 8] Check period for the angle of the galvanometer mirror,
It is a diagram showing the relationship between a non-recording period and a recording period.

[Explanation of symbols]

10 Laser beam recording device 12 He-Ne laser 18 AOM 34 Polygon mirror 48 Galvano mirror 70 Signal generation circuit 72 AOM driver 74 Control circuit

Claims (2)

[Claims] 1. A light beam scanning device comprising an acousto-optic element that divides an incident light beam into a plurality of beams, and performing two-dimensional scanning by performing main scanning and sub-scanning of the light beam by a scanning optical system, comprising: A light beam scanning device comprising: synchronization signal generating means for generating a synchronization signal for the two-dimensional scanning using one of the light beams split by the acousto-optic element. 2. An acousto-optic device that splits the light beam into a plurality of parts in a plurality of directions according to the frequency of the input signal and modulates the light beam to an intensity according to the amplitude of the input signal. A light beam scanning device that performs two-dimensional scanning by performing main scanning and sub-scanning using a scanning optical system, wherein a synchronization signal for the two-dimensional scanning is generated using one of the light beams split by the acousto-optic element. and a control means for controlling the amplitude of the signal so that the intensity of each of the light beams divided by the acousto-optic element becomes a predetermined value. Device.