Direct plate-making machine optical printing head based on double acousto-optic modulators and direct plate-making machine

Abstract

The utility model discloses a computer-to-plate optical printing head based on double acousto-optic modulators and a computer-to-plate, and belongs to the technical field of computer-to-plate, and the optical printing head used by the computer-to-plate comprises a first acousto-optic modulation unit, a second acousto-optic modulation unit and a third acousto-optic modulation unit, the first acousto-optic modulation unit is used for modulating and splitting half energy, matched with the first acousto-optic modulation unit in polarization direction, in the random polarization laser into first multi-channel laser; the second acousto-optic modulation unit is used for modulating and splitting the other half of energy of which the polarization direction is not matched with that of the first acousto-optic modulation unit but matched with that of the second acousto-optic modulation unit into second multi-channel laser; and the imaging unit is used for focusing the first multi-channel laser and the second multi-channel laser. According to the utility model, the energy of the polarized laser beam is fully utilized, the use efficiency of the laser is doubled, and the requirement on the power of the laser is correspondingly reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of direct plate making machines, and in particular relates to an optical printing head of a direct plate making machine based on a double acousto-optic modulator and a direct plate making machine. Background Art

[0002] Computer direct platemaking machines (CTP platemaking machines) are generally divided into four categories: internal drum type, external drum type, flatbed type, and curved type. Among these four types, the most commonly used are internal drum and external drum types; among them, high-end CTP platemaking machines with better performance all use external drum types. Figure 1 and 2 As shown, in the external drum platemaking system, the printing plate 3 is fixed on the outside of the imaging drum 2. When the imaging drum 2 rotates in the circumferential direction at a speed of several hundred revolutions per minute, the printing plate 3 rotates at the same speed as the imaging drum 2. At the same time, the laser emitted by the optical print head 1 irradiates the printing plate, and the optical print head 1 moves along the track 10 to complete the scanning of the printing plate 3. In general, in order to improve production efficiency, multiple laser beams are often used for scanning.

[0003] CTP plate-making machines are divided into many types according to the printing plates. The equipment used for printing flexographic plates is called flexographic plate-making machines, and its resolution is also required to be above 5080DPI. In addition, the printing format of flexographic plate-making machines is larger, the laser printing power is higher, and the thickness of the plate is thicker than the 0.27mm of traditional offset printing, and its thickness is about 0.9mm to 4mm. The printing power of flexographic plate-making machines is nearly an order of magnitude higher than the plate power of standard offset CTP equipment. The commonly used method is to use hundreds of watts of industrial fiber lasers to perform multi-channel spectral modulation on their beams for printing. The multi-channel spectral device usually uses an acousto-optic modulator.

[0004] The acousto-optic modulator uses an ultrasonic transducer to generate ultrasonic waves. The ultrasonic waves pass through the acousto-optic crystal. The crystal refractive index at the peak and the trough is different, making the acousto-optic crystal a phase grating. The laser beam passes through the phase grating and diffracts, thereby modulating the laser beam and forming multiple small light spots on the printing plate. The response speed of the acousto-optic modulator to adjust the light beam depends on the time it takes for the ultrasonic wave to pass through the entire beam diameter. Therefore, the thinner the laser beam passing through the acousto-optic modulator, the faster the acousto-optic modulator modulates the switching laser beam. For high-power lasers, the thinner the laser beam means the higher the laser energy density, and the acousto-optic crystal will not be able to withstand the laser power. Therefore, the thickness of the laser beam needs to be a reasonable value. Except for special polarization-maintaining lasers, the laser beam output through the optical fiber of industrial fiber lasers, whether single-mode or multi-mode, is a randomly polarized laser. When the acousto-optic modulator performs split light modulation, Bragg diffraction is used, and the light beam that can be effectively modulated is the linearly polarized light with the appropriate polarization direction. For randomly polarized lasers, a polarization beam splitter is required to reflect half of the laser and use the remaining half of the linearly polarized laser for split light modulation printing. Based on the above principle, the optical system of the optical print head 1 of the conventional CTP platemaking machine is as shown in the attached figure. Figure 3 As shown, it includes a polarization beam splitter 4, an acousto-optic modulator 5 and an imaging unit 6 which are sequentially arranged on the laser light path.

[0005] The optical system of the above-mentioned CTP platemaking machine needs to reflect half of the laser. However, the flexographic printing resolution requirement is very high, and the laser needs to use a pure single-mode laser. High-power single-mode lasers are not only expensive, but also more difficult to improve the beam quality. Therefore, if it is possible to use all the energy of the randomly polarized laser beam, the laser efficiency will be doubled, and the requirement for laser power will be reduced accordingly. Utility Model Content

[0006] The utility model provides a direct platemaking machine optical print head based on a dual acousto-optic modulator and a direct platemaking machine, so as to solve the problem that the optical system of the existing platemaking machine needs to reflect half of the laser, resulting in high power requirements of the laser for the platemaking machine.

[0007] In order to solve the above technical problems, the technical solution provided by the utility model is:

[0008] The utility model relates to an optical print head of a direct plate-making machine based on a dual acousto-optic modulator, which comprises:

[0009] A first acousto-optic modulation unit is used to modulate and split half of the energy of the randomly polarized laser light whose polarization direction matches the first acousto-optic modulation unit into a first multi-channel laser light;

[0010] A second acousto-optic modulation unit is used to modulate and split the other half of the energy whose polarization direction does not match the first acousto-optic modulation unit but matches the second acousto-optic modulation unit into a second multi-channel laser;

[0011] An imaging unit is used to focus the first multi-channel laser and the second multi-channel laser.

[0012] Preferably, the first acousto-optic modulation unit is a first acousto-optic modulator, the second acousto-optic modulation unit includes a half-wave plate and a second acousto-optic modulator, the half-wave plate is arranged between the first acousto-optic modulator and the second acousto-optic modulator, and the polarization directions matched by the first acousto-optic modulator and the second acousto-optic modulator are the same.

[0013] Preferably, the first acousto-optic modulation unit is a first acousto-optic modulator, the second acousto-optic modulation unit is a second acousto-optic modulator, and the polarization directions matched by the first acousto-optic modulator and the second acousto-optic modulator are perpendicular.

[0014] The utility model also relates to a direct plate-making machine based on a dual acousto-optic modulator, comprising an optical print head, an imaging drum and a printing plate, wherein the optical print head is arranged on the side of the imaging drum through a track parallel to the axis direction of the imaging drum, and the printing plate is wrapped on the outside of the imaging drum, and the optical print head comprises:

[0015] A first acousto-optic modulation unit is used to modulate and split half of the energy of the randomly polarized laser light whose polarization direction matches the first acousto-optic modulation unit into a first multi-channel laser light;

[0016] A second acousto-optic modulation unit is used to modulate and split the other half of the energy whose polarization direction does not match the first acousto-optic modulation unit but matches the second acousto-optic modulation unit into a second multi-channel laser;

[0017] An imaging unit is used to focus the first multi-channel laser and the second multi-channel laser.

[0018] Preferably, the first acousto-optic modulation unit is a first acousto-optic modulator, the second acousto-optic modulation unit includes a half-wave plate and a second acousto-optic modulator, the half-wave plate is arranged between the first acousto-optic modulator and the second acousto-optic modulator, and the polarization directions matched by the first acousto-optic modulator and the second acousto-optic modulator are the same.

[0019] Preferably, the first acousto-optic modulation unit is a first acousto-optic modulator, the second acousto-optic modulation unit is a second acousto-optic modulator, and the polarization directions matched by the first acousto-optic modulator and the second acousto-optic modulator are perpendicular.

[0020] Compared with the prior art, the technical solution provided by the utility model has the following beneficial effects:

[0021] The utility model relates to a first acousto-optic modulation unit in an optical print head of a direct plate-making machine based on a dual acousto-optic modulator, which is used to modulate and split half of the energy of a randomly polarized laser whose polarization direction matches the first acousto-optic modulation unit into a first multi-channel laser; the second acousto-optic modulation unit is used to modulate and split the other half of the energy whose polarization direction does not match the first acousto-optic modulation unit but matches the second acousto-optic modulation unit into a second multi-channel laser; and finally, the first multi-channel laser and the second multi-channel laser are used for scanning. The utility model reuses half of the laser beam reflected in the optical system of the original optical print head, and the energy of the polarized laser beam is fully utilized, the use efficiency of the laser is doubled, and the requirement for the laser power is also reduced accordingly. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a stereogram of a plate-setter;

[0023] Figure 2 It is a schematic diagram of the working status of the direct plate-making machine;

[0024] Figure 3 It is a schematic diagram of the optical path system of the optical print head of the existing direct plate making machine;

[0025] Figure 4 It is a schematic diagram of the optical path system of the optical print head involved in Example 1 of the utility model;

[0026] Figure 5 It is a light spot diagram formed on a printing plate by the direct plate-making machine involved in Embodiment 1 of the utility model;

[0027] Figure 6 It is a front view of the optical path system of the optical print head involved in Embodiments 2 and 3 of the present utility model;

[0028] Figure 7 It is a top view of the optical path system of the optical print head involved in Embodiments 2 and 3 of the utility model;

[0029] Figure 8 It is a light spot diagram formed on a printing plate by the direct plate-making machine involved in Embodiment 2 of the utility model;

[0030] Fig. 9 It is a light spot diagram formed on a printing plate by the direct plate-making machine involved in Example 3 of the utility model.

[0031] Figure numerals: 1-optical print head, 2-imaging drum, 3-printing plate, 4-polarization beam splitter, 5-acoustic-optic modulator, 6-imaging unit, 7-first acousto-optic modulator, 8-second acousto-optic modulator, 9-half-wave plate, 10-track, 11-randomly polarized laser, 12-first multi-channel laser, 13-outgoing light, 14-second multi-channel laser. DETAILED DESCRIPTION

[0032] In order to further understand the content of the utility model, the utility model is described in detail in conjunction with embodiments. The following embodiments are used to illustrate the utility model but are not used to limit the scope of the utility model.

[0033] Example 1

[0034] See attached Figure 1 and 2 As shown in FIG. 1 , the direct platemaking machine based on dual acousto-optic modulators involved in this embodiment includes an optical print head, an imaging drum and a printing plate. The optical print head is arranged on the side of the imaging drum through a track parallel to the axis direction of the imaging drum, and the printing plate is wrapped around the outside of the imaging drum. Figure 4 As shown, the optical path system of the optical print head includes a first acousto-optic modulation unit, a second acousto-optic modulation unit and an imaging unit 6 arranged along the laser optical path. The first acousto-optic modulation unit is a first acousto-optic modulator 7, the second acousto-optic modulation unit includes a half-wave plate 9 and a second acousto-optic modulator 8, and the polarization directions matched by the first acousto-optic modulator 7 and the second acousto-optic modulator 8 are the same.

[0035] The printing method of the direct plate-making machine based on the dual acousto-optic modulator involved in this embodiment comprises the following steps:

[0036] Step 1. The randomly polarized laser 11 is incident on the first AOM 7, and the first AOM 7 modulates and splits half of the energy of the randomly polarized laser 11 whose polarization direction matches the first AOM 7 into the first multi-channel laser 12, and the remaining half of the energy whose polarization direction does not match the first AOM 7 passes through the first AOM 7 as the outgoing light 13;

[0037] Step 2. The first multi-channel laser 12 and the outgoing light 13 enter the second acousto-optic modulation unit simultaneously, specifically:

[0038] Step 2.1. The first multi-channel laser 12 and the outgoing light 13 enter the half-wave plate 9, and the half-wave plate 9 rotates the polarization directions of the first multi-channel laser 12 and the outgoing light 13 by 90°;

[0039] Step 2.2. The first multi-channel laser 12 and the outgoing light 13 after polarization direction rotation enter the second AOM 8, and the second AOM 8 modulates the outgoing light 13 into the second multi-channel laser 14. The first multi-channel laser 12 passes through the second AOM 8 because its polarization direction does not match that of the second AOM 8. The first multi-channel laser 12 and the second multi-channel laser 14 formed by steps 1 and 2 are arranged along a straight line.

[0040] Step 3. The imaging unit 6 focuses each laser beam of the first multi-channel laser 12 and the second multi-channel laser 14, and projects the first multi-channel laser 12 and the second multi-channel laser 14 onto the printing plate. At this time, the modulation angles of the first acousto-optic modulator 7 and the second acousto-optic modulator 8 are calculated so that the light spots projected by the first multi-channel laser 12 and the second multi-channel laser 14 onto the printing plate are arranged in a straight line and adjacent light spots are arranged closely, such as Figure 5 As shown, this light spot is used for scanning and printing.

[0041] Example 2

[0042] Refer to the attached Figure 1 and 2 As shown in FIG. 1 , the direct platemaking machine based on dual acousto-optic modulators involved in this embodiment includes an optical print head, an imaging drum and a printing plate. The optical print head is arranged on the side of the imaging drum through a track parallel to the axis direction of the imaging drum, and the printing plate is wrapped around the outside of the imaging drum. Figure 6 and 7 As shown, the optical path system of the optical print head includes a first acousto-optic modulation unit, a second acousto-optic modulation unit and an imaging unit 6 arranged along the laser optical path. The first acousto-optic modulation unit is a first acousto-optic modulator 7, the second acousto-optic modulation unit is a second acousto-optic modulator 8, and the polarization directions matched by the first acousto-optic modulator 7 and the second acousto-optic modulator 8 are perpendicular.

[0043] The printing method of the direct plate-making machine based on the dual acousto-optic modulator involved in this embodiment comprises the following steps:

[0044] Step 1. The randomly polarized laser 11 is incident on the first AOM 7, and the first AOM 7 modulates and splits half of the energy of the randomly polarized laser 11 whose polarization direction matches the first AOM 7 into the first multi-channel laser 12, and the remaining half of the energy whose polarization direction does not match the first AOM 7 passes through the first AOM 7 as the outgoing light 13;

[0045] Step 2. The first multi-channel laser 12 and the outgoing light 13 enter the second AOM 8 at the same time. Since the polarization direction of the first multi-channel laser 12 is at an angle of 90 degrees to the polarization direction matched by the second AOM 8, the first multi-channel laser 12 directly passes through the second AOM 8, and the polarization direction of the outgoing light 13 matches the second AOM 8. The second AOM 8 modulates the outgoing light 13 into the second multi-channel laser 14.

[0046] The arrangement direction of each laser in the second multi-channel laser 14 modulated in step 2 is perpendicular to the arrangement direction of each laser in the first multi-channel laser 12 modulated in step 1.

[0047] Step 3. The imaging unit 6 focuses each laser beam of the first multi-channel laser 12 and the second multi-channel laser 14, and projects the first multi-channel laser 12 and the second multi-channel laser 14 onto the printing plate. The number of lasers in the second multi-channel laser 14 is the same as the number of lasers in the first multi-channel laser 12. At this time, the modulation angle of each laser in the first multi-channel laser 12 is controlled by the first acousto-optic modulator 7, and the modulation angle of each laser in the second multi-channel laser 14 is controlled by the second acousto-optic modulator 8, so that the light spots formed when the lasers of adjacent channels in the first multi-channel laser 12 are projected onto the printing plate are tangent, and the light spots formed when the lasers of adjacent channels in the second multi-channel laser 14 are projected onto the printing plate are tangent, as shown in FIG. Figure 8 As shown, the light spot is used for scanning and printing. During scanning and printing, the angles between the scanning direction and the arrangement directions of the first multi-channel laser 12 and the second multi-channel laser 14 are both 45°. For each laser in the first multi-channel laser 12, there is a laser in the second multi-channel laser 14 in the scanning direction. In this way, the first multi-channel laser 12 and the second multi-channel laser 14 will overlap one by one in the scanning direction. A delay is set for each light spot generated by modulated spectroscopy so that the imaging point on the printing work surface is at the same place, thereby achieving the overlap of the patterns printed by the multi-channel light spots after spectroscopy by the two acousto-optic modulators, and each pixel of the printed pattern is exposed twice, without any waste of laser energy.

[0048] Example 3

[0049] Refer to the attached Figure 1 and 2 As shown in FIG. 1 , the direct platemaking machine based on dual acousto-optic modulators involved in this embodiment includes an optical print head, an imaging drum and a printing plate. The optical print head is arranged on the side of the imaging drum through a track parallel to the axis direction of the imaging drum, and the printing plate is wrapped around the outside of the imaging drum. Figure 6 and 7 As shown, the optical path system of the laser print head includes a first acousto-optic modulation unit, a second acousto-optic modulation unit and an imaging unit 6 arranged along the laser optical path. The first acousto-optic modulation unit is a first acousto-optic modulator 7, the second acousto-optic modulation is a second acousto-optic modulator 8, and the polarization directions matched by the first acousto-optic modulator 7 and the second acousto-optic modulator 8 are perpendicular.

[0050] The printing method of the direct plate-making machine based on the dual acousto-optic modulator involved in this embodiment comprises the following steps:

[0051] Step 1. The randomly polarized laser 11 is incident on the first AOM 7, and the first AOM 7 modulates and splits half of the energy of the randomly polarized laser 11 whose polarization direction matches the first AOM 7 into the first multi-channel laser 12, and the remaining half of the energy whose polarization direction does not match the first AOM 7 passes through the first AOM 7 as the outgoing light 13;

[0052] Step 2. The first multi-channel laser 12 and the outgoing light 13 enter the second AOM 8 at the same time. Since the polarization direction of the first multi-channel laser 12 is at an angle of 90 degrees to the polarization direction matched by the second AOM 8, the first multi-channel laser 12 directly passes through the second AOM 8, and the polarization direction of the outgoing light 13 matches the second AOM 8. The second AOM 8 modulates the outgoing light 13 into the second multi-channel laser 14.

[0053] The arrangement direction of each laser in the second multi-channel laser 14 modulated in step 2 is perpendicular to the arrangement direction of each laser in the first multi-channel laser 12 modulated in step 1.

[0054] Step 3. The imaging unit 6 focuses each laser beam of the first multi-channel laser 12 and the second multi-channel laser 14, and projects the first multi-channel laser 12 and the second multi-channel laser 14 onto the printing plate. The number of lasers in the second multi-channel laser 14 is the same as the number of lasers in the first multi-channel laser 12. At this time, the modulation angle of each laser in the first multi-channel laser 12 is controlled by the first acousto-optic modulator 7, and the modulation angle of each laser in the second multi-channel laser 14 is controlled by the second acousto-optic modulator 8, so that the spots formed when the lasers of adjacent channels in the first multi-channel laser 12 are projected onto the printing plate are arranged at intervals, and the spots formed when the lasers of adjacent channels in the second multi-channel laser 14 are projected onto the printing plate are arranged at intervals, the number of lasers in the second multi-channel laser 14 is the same as the number of lasers in the first multi-channel laser 12, the angles between the scanning direction and the arrangement direction of the first multi-channel laser 12 and the arrangement direction of the second multi-channel laser 14 are both 45°, and the lasers in the first multi-channel laser 12 and the second multi-channel laser 14 are staggered in the direction perpendicular to the scanning direction, as shown in FIG. Fig. 9 As shown, this light spot is used for scanning and printing.

[0055] At this time, there is a gap between the light spots of each channel of each laser beam, and the light beam of the second AOM 8 can just be added into the gap of the first AOM 7, so that the total number of equivalent printing channels of the two AOMs is doubled, and there is no waste of laser energy.

[0056] The above is a detailed description of the utility model in combination with the embodiments, but the contents described are only preferred embodiments of the utility model and cannot be considered to limit the scope of implementation of the utility model. All equivalent changes and improvements made within the scope of application of the utility model should still fall within the scope of the patent coverage of the utility model.

Claims

1. An optical print head for a direct plate-making machine based on a dual acousto-optic modulator, characterized in that: It includes: A first acousto-optic modulation unit is used to modulate and split half of the energy of the randomly polarized laser light whose polarization direction matches the first acousto-optic modulation unit into a first multi-channel laser light; A second acousto-optic modulation unit is used to modulate and split the other half of the energy whose polarization direction does not match the first acousto-optic modulation unit but matches the second acousto-optic modulation unit into a second multi-channel laser; An imaging unit is used to focus the first multi-channel laser and the second multi-channel laser.

2. The optical print head for a direct-to-plate machine based on a dual acousto-optic modulator according to claim 1, characterized in that: The first acousto-optic modulation unit is a first acousto-optic modulator, and the second acousto-optic modulation unit includes a half-wave plate and a second acousto-optic modulator, the half-wave plate is arranged between the first acousto-optic modulator and the second acousto-optic modulator, and the polarization directions matched by the first acousto-optic modulator and the second acousto-optic modulator are the same.

3. The optical print head for a direct-to-plate machine based on a dual acousto-optic modulator according to claim 1, characterized in that: The first acousto-optic modulation unit is a first acousto-optic modulator, and the second acousto-optic modulation unit is a second acousto-optic modulator. The polarization directions matched by the first acousto-optic modulator and the second acousto-optic modulator are perpendicular.

4. A direct platemaking machine based on a dual acousto-optic modulator, comprising an optical print head, an imaging drum and a printing plate, wherein the optical print head is arranged on the side of the imaging drum through a track parallel to the axis direction of the imaging drum, and the printing plate is wrapped on the outside of the imaging drum, characterized in that: The optical print head comprises: A first acousto-optic modulation unit is used to modulate and split half of the energy of the randomly polarized laser light whose polarization direction matches the first acousto-optic modulation unit into a first multi-channel laser light; A second acousto-optic modulation unit is used to modulate and split the other half of the energy whose polarization direction does not match the first acousto-optic modulation unit but matches the second acousto-optic modulation unit into a second multi-channel laser; An imaging unit is used to focus the first multi-channel laser and the second multi-channel laser.

5. The direct plate-making machine based on dual acousto-optic modulator according to claim 4, characterized in that: The first acousto-optic modulation unit is a first acousto-optic modulator, and the second acousto-optic modulation unit includes a half-wave plate and a second acousto-optic modulator, the half-wave plate is arranged between the first acousto-optic modulator and the second acousto-optic modulator, and the polarization directions matched by the first acousto-optic modulator and the second acousto-optic modulator are the same.

6. The direct plate-making machine based on dual acousto-optic modulator according to claim 4, characterized in that: The first acousto-optic modulation unit is a first acousto-optic modulator, and the second acousto-optic modulation unit is a second acousto-optic modulator. The polarization directions matched by the first acousto-optic modulator and the second acousto-optic modulator are perpendicular.

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