JP3583577B2 - Laser exposure equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laser exposure apparatus, and more particularly to a laser exposure apparatus that scans a recording medium with different laser beams of at least two wavelengths to expose and form a color image.
[0002]
[Prior art]
Conventionally, as a laser exposure apparatus for exposing and forming a color image, a gas laser of three wavelengths corresponding to BGR (argon laser, helium neon laser, or the like) and an acousto-optic modulator (hereinafter abbreviated as AOM) are combined. There is known an apparatus to be used or an apparatus having a structure in which a photosensitive material sensitive to a red wavelength or more is used for all three layers of CMY, and a semiconductor laser of three wavelengths is directly modulated (internally modulated) and exposed.
[0003]
[Problems to be solved by the invention]
However, an argon laser, which is often used as a B light source among gas lasers, has a problem that the apparatus size is large and the cost is high.
Further, in the conventional modulation by the AOM, the laser beam from the gas laser is directly incident on the AOM. In this case, however, the exposure speed is limited by the modulation speed of the AOM, and the exposure speed is sufficiently increased. Could not be converted.
[0004]
On the other hand, if all three layers of CMY use photosensitive materials that are sensitive to red wavelengths or more, relatively inexpensive semiconductor lasers can be used as all light sources. However, photosensitive materials having the above characteristics are designed and manufactured. However, there is a problem that storage is difficult and the price of the photographic material itself becomes high. In addition, there is a problem that using three or more red wavelengths causes three wavelengths to approach each other, which may cause interference between adjacent wavelengths.
[0005]
The present invention has been made in view of the above problems, and has as its object to reduce the size and cost of a laser exposure apparatus.
Another object of the present invention is to provide a laser exposure apparatus capable of exposing a stable color image at a high speed.
[0006]
[Means for Solving the Problems]
Therefore, according to the first aspect of the present invention, there is provided a laser exposure apparatus for exposing and forming an image by scanning a recording medium with different laser beams having at least two wavelengths. Exposure timing adjusting means which is constituted by a combination of a laser beam whose light quantity is modulated by a modulation element and matches the exposure timing of the directly modulated laser beam with the laser beam whose light quantity is modulated by the acousto-optic modulation element. The configuration was provided with.
[0007]
According to this configuration, image exposure is performed by combining a laser beam that is directly modulated (internally modulated) and a laser beam that is externally modulated by an acousto-optic conversion element (AOM). At this time, since there is a delay in the modulation of the AOM with respect to the case where the laser beam is directly modulated, the configuration is provided with an exposure timing adjusting means for matching the exposure timing. The exposure timing can be matched by shifting the beam position or delaying the modulation data for performing direct modulation by the delay of the AOM.
According to the second aspect of the present invention, the laser beam whose light amount is modulated by the direct modulation is a semiconductor laser, and the laser beam whose light amount is modulated by the acousto-optic modulator is a gas laser or a solid laser.
[0008]
In such a configuration, the semiconductor laser performs light quantity modulation in accordance with an image signal by turning on and off a current flowing through the semiconductor laser, and a constant output from the gas laser or the solid-state laser is converted into an image signal by an acousto-optic modulator (AOM). Is performed in accordance with the light amount modulation. It is preferable to use a He-Ne laser as the gas laser, and it is preferable to use a laser diode (LD) pumped solid laser as the solid laser. Further, one of the CMY photosensitive layers as a recording medium is a photosensitive material having sensitivity to infrared light, the light source is shifted to infrared light, and a gas laser or a solid laser is used as a short wavelength light source (G light source). It is preferable to use a semiconductor laser as a light source of two wavelengths other than the above (R and infrared light sources).
[0009]
According to a third aspect of the present invention, there is provided a beam shaping optical unit for adjusting the beam shape of the semiconductor laser whose light intensity is modulated by the direct modulation to the beam shape of a gas laser or a solid laser whose light intensity is modulated by the acousto-optic modulator. A configuration was provided.
In general, the beam shape of a semiconductor laser is elliptical, whereas the beam shape of a gas laser or solid laser is a perfect circle, so the beam shape of a semiconductor laser is made a perfect circle, and the beam shape of each wavelength is made the same. Things.
[0010]
In the invention according to claim 4, an incident beam diameter reducing means for reducing a diameter of a laser beam incident on the acousto-optic modulator, and a diameter of the laser beam emitted from the acousto-optic modulator is reduced by the incident beam diameter reducing means. And a beam diameter returning means for returning to a diameter before being reduced.
Since the response speed in the acousto-optic conversion element (AOM) depends on the beam diameter, the beam diameter is reduced before being incident on the AOM to improve the response speed, and after being modulated by the AOM, the diameter of the laser beam is reduced. Undo.
[0012]
According to a fifth aspect of the invention, the laser beam is reduced to a desired beam diameter, and a reduction optical unit for projecting the laser beam as a parallel beam having the reduced diameter on the recording medium is provided.
According to this configuration, when exposing and scanning the recording medium with the reduced diameter, a parallel beam having the reduced diameter, that is, a beam whose diameter does not change depending on the distance from the lens, is projected onto the recording medium.
[0013]
In the invention according to claim 6 , the recording medium is exposed and scanned with a plurality of laser beams for each wavelength, and the acousto-optic conversion element simultaneously modulates the plurality of laser beams. Pitch conversion means is provided for adjusting the distance between the laser beams modulated by the direct modulation to the distance between the laser beams in the conversion element.
[0014]
According to this configuration, the exposure and scanning are performed with a plurality of laser beams for each wavelength, and when the acousto-optic conversion element is configured to simultaneously modulate the plurality of laser beams, the acousto-optic conversion element simultaneously modulates the plurality of laser beams. The interval between the directly modulated laser beams is converted so that the interval between the directly modulated laser beams matches the interval between the plurality of laser beams.
[0015]
In the invention according to claim 7, a plurality of laser beams whose light amounts are modulated by the direct modulation whose beam intervals are adjusted by the pitch conversion means and a plurality of laser beams whose light amounts are modulated by the acousto-optic conversion element are simultaneously formed. A configuration is provided that includes pitch reduction means for reducing the pitch to the same pitch.
According to such a configuration, the laser beam modulated by the acousto-optic conversion element (AOM) and the laser beam directly modulated, which have been converted to the same beam interval in advance, are collectively reduced to the same pitch, and the recording medium is reduced. Exposure is scanned upward.
[0016]
In the invention according to claim 8, the number of mirrors interposed in the optical path of the long wavelength laser beam is configured to be smaller than that of the short wavelength laser beam.
According to this configuration, the laser beam having a longer wavelength is configured to be exposed on the recording medium via a smaller number of mirrors than the laser beam having the shorter wavelength. The mirror is an optical mirror for which assembly adjustment is performed. For a long-wavelength laser beam, the number of mirrors requiring the assembly adjustment is smaller than for other short-wavelength laser beams. For example, when an infrared wavelength is used as a long wavelength, the number of mirrors that need to be adjusted is reduced for a laser beam having an infrared wavelength that is difficult to see.
[0017]
【The invention's effect】
According to the first or second aspect of the present invention, by using a laser beam that is directly modulated and a laser beam that is modulated in amount by an acousto-optic modulator, a large and expensive light source can be avoided. In addition, there is an effect that it is possible to use a low-cost recording medium (sensitive material) which can be easily manufactured and stored. At this time, even if there is a delay in the light amount modulation by the acousto-optic modulator with respect to the directly modulated laser beam, exposure scanning can be performed with the same exposure timing.
[0018]
According to the third aspect of the invention, it is possible to correct the difference between the beam shapes of the semiconductor laser and the gas or solid-state laser, and to perform exposure scanning as a beam having the same shape.
According to the fourth aspect of the present invention, the response of the acousto-optic modulator can be improved by reducing the beam diameter incident on the acousto-optic modulator.
[0019]
According to the fifth aspect of the invention, the laser beam is projected as a parallel beam onto the recording medium, so that exposure and scanning can be performed with a constant beam diameter even when the distance between the recording surface and the optical head changes. There is an effect that can be.
[0020]
According to the sixth aspect of the present invention, in the configuration using the acousto-optic modulator that simultaneously modulates a plurality of laser beams, each wavelength is adjusted by adjusting the interval of the laser beam directly modulated to the beam interval in the acousto-optic modulator. This has the effect of improving the overlay accuracy of.
According to the seventh aspect of the present invention, since the beam interval for each wavelength is previously adjusted and the beam interval is reduced collectively, the resolution and the number of lines can be easily changed. .
[0021]
According to the eighth aspect of the present invention, there is an effect that the number of adjustments of the optical mirror related to the laser beam having a wavelength that is difficult to see is reduced, thereby facilitating the assembly adjustment.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described.
FIG. 1 is a system configuration diagram schematically showing a laser exposure apparatus according to an embodiment, in which a photosensitive material (recording medium) is exposed and scanned using a laser beam of three wavelengths to obtain a color image.
[0023]
Specifically, as shown in FIG. 2, a CMY layer of a photosensitive material as a recording medium is exposed by using laser beams of three wavelengths of green G, red R, and infrared IR. In other words, one of the BGR photosensitive layers is a photosensitive material having sensitivity to infrared light, and the light source is shifted to infrared light.
A He-Ne laser that is a gas laser is used as the green G laser, and a semiconductor laser (LD) is used as the red R and infrared IR lasers.
[0024]
Semiconductor lasers are generally smaller in device size and lower in cost than gas lasers. If semiconductor lasers can be used for all three wavelengths, the size and cost of an exposure system can be greatly reduced. However, in this case, a light-sensitive material sensitive to the red wavelength or more is required for all three CMY layers due to the limitation of the oscillation wavelength of the semiconductor laser. However, a light-sensitive material having such characteristics is difficult and expensive to manufacture and store. . Therefore, an Ar laser generally used as a blue B laser is not used, particularly because the device size is large and the cost is high. On the other hand, a He-Ne laser is used as a green G laser. In this case, a light-sensitive material sensitive to a green wavelength or more can be used as the light-sensitive material, thereby reducing the cost and size of the exposure system.
[0025]
The green G laser may be a solid laser, in particular, an LD pumped solid laser that generates green light by SHG (Second Harmonic Generation), instead of the He-Ne laser that is a gas laser.
Here, the configuration of the laser exposure apparatus shown in FIG. 1 will be described in detail.
As described above, the laser exposure apparatus shown in FIG. 1 uses a He-Ne laser as a green G laser, and uses a semiconductor laser (LD) as a red R and infrared IR laser.
[0026]
A laser beam (green laser beam) from a He-Ne laser 101 as a green G laser is output by an acousto-optic modulator (hereinafter abbreviated as AOM) 102 according to a modulation signal (image signal). The light amount is modulated, and the semiconductor lasers (LD) 103 and 104 as red R and infrared IR lasers are light amount modulated by direct modulation (internal modulation) according to a modulation signal (image signal).
[0027]
Then, the laser beam 105 modulated in the light amount by the AOM 102 is reflected by the reflection mirror 106, passes through the two dichroic mirrors 107 and 108, is reflected by the reflection mirror 109, and is formed on the rotating drum 111 by the imaging lens 110. Is projected onto a light-sensitive material (recording medium) 112 fixed to.
The laser beam (red laser beam) 113 from the semiconductor laser 103 is reflected by the dichroic mirror 107, then passes through the dichroic mirror 108, is reflected by the reflecting mirror 109, and is formed on the rotating drum 111 by the imaging lens 110. The image is projected onto the fixed photosensitive material (recording medium) 112.
[0028]
Further, a laser beam (infrared laser beam) 114 from the semiconductor laser 104 is reflected by the dichroic mirror 108, then reflected by the reflecting mirror 109, and fixed on the rotating drum 111 by the image forming lens 110. (Recording medium) 112.
As described above, the number of mirrors provided in the middle of the optical path of the infrared laser beam 114 is smaller than that of the other two wavelength laser beams. As a result, with respect to the infrared laser beam 114, which is a long-wavelength laser which is the least visible, the number of mirrors requiring mirror adjustment is small, and assembly adjustment can be facilitated.
[0029]
The rotary drum 111 is driven to rotate around its rotation axis 111a, whereby main scanning is performed. On the other hand, the optical head including the reflection mirror 109 and the imaging lens 110 is rotated by the rotation axis 111a. The sub-scan is performed by driving in the direction parallel to
Between the AOM 102 and the He-Ne laser 101, a cylindrical lens 115 (incident beam diameter reducing means) for reducing the beam diameter of the laser beam 105 incident on the AOM 102 is disposed. A cylindrical lens 116 (beam diameter returning means) for returning the beam diameter reduced by the cylindrical lens 115 to the original diameter is disposed between the reflecting mirror 106 and the reflecting mirror 106.
[0030]
Since the response of the AOM 102 decreases when the diameter of the incident beam is large, the diameter of the laser beam 105 incident on the AOM 102 is reduced by the cylindrical lens 115 to improve the response of the AOM 102. . Then, after receiving the light quantity modulation in the AOM 102, the beam diameter is returned by the cylindrical lens 116.
[0031]
By the way, the beam shape of the laser beam 105 from the He-Ne laser 101 is substantially a perfect circle, whereas the beam shape of the laser beams 113 and 114 from the semiconductor lasers (LD) 103 and 104 is elliptical. For this reason, the elliptical laser beams 113 and 114 are shaped into a perfect circle which is the beam shape of the laser beam 105 by cylindrical lenses (or prism pairs) 117 and 118 as beam shaping optical means. As a result, all three laser beams are exposed and scanned in a perfect circular beam shape.
[0032]
Further, the imaging lens 110 (reducing optical means) is configured as shown in FIG.
As shown in FIG. 3, in the imaging lens 110, the three-wavelength laser beams 105, 113, and 114 (parallel beams) are projected onto the photosensitive material 112 as parallel beams with reduced beam diameters. With such a configuration using the imaging lens 110 1, even if the distance between the imaging lens 110 (optical head) and the recording surface changes due to the swing of the rotating drum 111, the laser beam exposed on the photosensitive material 112 1 Diameter does not change.
[0033]
Incidentally, there is a difference in response speed between the modulation by the AOM 102 and the direct modulation by the semiconductor lasers 103 and 104. Since the direct modulation has a higher response, the AOM 102 and the semiconductor lasers 103 and 104 have the same configuration as shown in FIG. When the modulation signals at the same timing are given to 104, the beams that fall on the same point on the drum surface are shifted. Therefore, as shown in FIG. 4, the laser beam 105 from the He—Ne laser 101 modulated by the AOM 102 has advanced in the drum rotation direction more than the laser beams 113 and 114 from the semiconductor lasers (LD) 103 and 104. It is preferable to provide a delay correction optical system 120 (exposure timing adjusting means) for exposing the position.
[0034]
The delay correction optical system 120 is composed of two reflection mirrors 121 and 122 arranged parallel to each other, and shifts the laser beam 105 from the AOM 102 in the main scanning direction.
If the delay correction optical system 120 as described above is provided, the portion exposed by the semiconductor lasers (LD) 103 and 104 will be exposed by the He-Ne laser 101 with a delay, and as a result, The He-Ne laser 101 and the semiconductor lasers (LD) 103, 104 are superposed and exposed on the recording surface even if the response of the AOM 102 to the modulation is slower than the direct modulation of the semiconductor lasers (LD) 103, 104. Can be.
[0035]
Instead of optically shifting the laser beam 105 from the He-Ne laser 101, the beam positions of the laser beams 113 and 114 from the semiconductor lasers (LD) 103 and 104 are shifted in the direction opposite to the rotation direction of the drum. It is good also as composition. That is, any configuration may be used as long as the laser beam 105 from the He-Ne laser 101 is exposed with a delay in the main scanning direction by the response delay of the AOM 102.
[0036]
In the above description, the response delay of the AOM 102 is optically corrected. However, it is also possible to compensate for the response delay by delay correction of modulation data (image data).
In the example shown in FIG. 5, the LD modulated data 130 and AOM modulated data 131 are D / A converted by D / A converters 132 and 133, respectively, and provided to the semiconductor lasers (LD) 103 and 104 and the AOM 102, respectively. Before the D / A conversion, the LD modulation data 130 is delayed by the response delay of the AOM 102 by the delay correction circuit 134 (exposure timing adjustment means).
[0037]
According to this configuration, the semiconductor lasers 103 and 104 are directly modulated in accordance with the delayed modulation data. However, since there is a delay in the light quantity modulation by the AOM 102 based on the previous modulation data, the laser beam after the light quantity modulation from the AOM 102 At the stage of emission, the laser beams modulated by the modulation data at the same timing are respectively exposed.
[0038]
By the way, in the embodiment described above, exposure and scanning are performed with one laser beam for each wavelength, but as shown in FIG. 6, exposure and scanning are performed using a plurality of laser beams for each wavelength. A configuration may be used.
In the example shown in FIG. 6, a case is shown in which exposure scanning is performed with three laser beams for each wavelength. However, the number of beams for each wavelength is not limited to three.
[0039]
In FIG. 6, a green laser beam 105 from a He-Ne laser 101 is divided into three beams by a beam separator 141, modulated by a multi-AOM 142, reflected by a reflection mirror 106, and transmitted through dichroic mirrors 107 and 108. Then, the light is incident on the imaging lens 110.
Also here, cylindrical lenses 115 and 116 are interposed on both sides of the multi-AOM 142 to reduce the beam diameter before entering the multi-AOM 142 to improve the responsiveness of the multi-AOM 142. After receiving the light quantity modulation, the beam diameter is returned to the original one.
[0040]
On the other hand, three red R semiconductor lasers (LD) 103 and three infrared IR semiconductor lasers (LD) 104 are provided. Then, the light is shaped into a perfect circle, which is the beam shape of the He-Ne laser 101, by the cylindrical lenses (or prism pairs) 117 and 118 for each wavelength, and then enters the beam compressors 143 and 144.
[0041]
In the beam compressors 143 and 144 (pitch conversion means), the beam intervals (inter-beam pitch) of the three red laser beams and the three infrared laser beams are reduced to match the beam intervals in the multi-AOM 142. You.
The three red laser beams and the three infrared laser beams with the reduced beam intervals are reflected by dichroic mirrors 107 and 108 and enter the imaging lens 110.
[0042]
In the imaging lens 110, the laser beams for each wavelength aligned at the same beam interval are simultaneously reduced to the same beam interval at the same time (pitch reducing means), and each laser beam is projected as a parallel beam onto the recording surface. Let it.
In the above-described embodiment, the exposure method is the outer cylindrical exposure method. However, the present invention is not limited to this. For example, a configuration in which scanning is performed by a polygon mirror may be used.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram schematically showing a laser exposure apparatus according to an embodiment.
FIG. 2 is a diagram showing each wavelength of a laser beam in the embodiment.
FIG. 3 is a diagram showing an imaging lens system in the embodiment.
FIG. 4 is a system configuration diagram showing a configuration for optically correcting a response delay of an AOM.
FIG. 5 is a system configuration diagram showing a configuration for correcting a response delay of an AOM by a delay of modulation data.
FIG. 6 is a system configuration diagram showing an embodiment in which exposure is performed using a plurality of beams for each wavelength.
[Explanation of symbols]
101 He-Ne laser 102 Acousto-optic modulator (AOM)
103, 104 Semiconductor laser 105, 106 Cylindrical lens 106, 109 Reflecting mirror 107, 108 Dichroic mirror 110 Imaging lens 111 Rotating drum 112 Sensitive material 115, 116 Cylindrical lens 120 Delay correction optical system 134 Delay correction circuit 141 Beam separator 142 Multi-AOM
143, 144 Beam compressor

Claims (8)

A laser exposure apparatus that scans a recording medium with at least two different wavelengths of laser beams to expose and form an image,
It is composed of a combination of a laser beam whose light intensity is modulated by direct modulation and a laser beam whose light intensity is modulated by an acousto-optic modulator .
A laser exposure apparatus, comprising: an exposure timing adjusting unit that matches exposure timings of the directly modulated laser beam and the laser beam whose light quantity is modulated by the acousto-optic modulator . 2. The laser exposure apparatus according to claim 1, wherein the laser beam whose light intensity is modulated by the direct modulation is a semiconductor laser, and the laser beam whose light intensity is modulated by the acousto-optic modulator is a gas laser or a solid laser. A beam shaping optical unit for adjusting a beam shape of the semiconductor laser whose light intensity is modulated by the direct modulation to a beam shape of a gas laser or a solid-state laser whose light intensity is modulated by the acousto-optic modulator. 3. The laser exposure apparatus according to 2. Incident beam diameter reducing means for reducing the diameter of the laser beam incident on the acousto-optic modulator, and reducing the diameter of the laser beam emitted from the acousto-optic modulator to a diameter before being reduced by the incident beam diameter reducing means. The laser exposure apparatus according to claim 1, further comprising a returning beam diameter returning unit. While reducing the laser beam to a desired beam diameter, any one of claims 1-4, characterized in that with a reduced optical means for projecting a parallel beam of reduced diameter on the recording medium A laser exposure apparatus according to claim 1. A configuration for exposing and scanning a recording medium with a plurality of laser beams for each wavelength, wherein the acousto-optic conversion element simultaneously modulates a plurality of laser beams, and a laser beam interval in the acousto-optic conversion element, The laser exposure apparatus according to any one of claims 1 to 5 , further comprising a pitch conversion unit that adjusts an interval between laser beams that are light-quantity modulated by the direct modulation. Pitch reduction means for simultaneously reducing the plurality of laser beams whose light amounts are modulated by the direct modulation whose beam intervals are adjusted by the pitch conversion means and the plurality of laser beams whose light amounts are modulated by the acousto-optic conversion element to the same pitch. The laser exposure apparatus according to claim 6, further comprising: Laser exposure apparatus according to any one of claims 1-7, characterized in that the number of mirror interposed in the optical path of a long wavelength laser beam is configured to be less than the short wavelength laser beam .

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