JP4472624B2 - Resolution switching method in inner drum type multi-beam exposure system - Google Patents

Description

  The present invention relates to a resolution switching method in an inner drum type multi-beam exposure system for performing exposure processing by scanning a photosensitive surface disposed on an inner surface of a cylindrical drum by a light beam scanning optical system.

  In general, an inner drum exposure apparatus (inner surface scanning type light beam scanning exposure apparatus) that performs a scanning exposure process by guiding a light beam such as a laser beam onto a photosensitive surface of a recording medium disposed on the inner peripheral surface of a cylindrical drum. Is widely used. The recording medium on which the image is exposed and recorded is subjected to an automatic developing machine as necessary, and the latent image formed on the recording medium is converted into a visible image. In such an inner drum exposure apparatus, it is desired to use a multi-beam in order to enable high-speed exposure processing.

  2. Description of the Related Art Conventionally, as a technique for performing exposure processing by using a multi-beam by an inner drum exposure apparatus, there is a method of using a polarized light for multi-beam. In such an inner drum exposure apparatus, a combined light beam obtained by synthesizing two light beams that have been made into two circularly polarized beams whose rotation directions are opposite to each other by the light beam output unit so that their optical axes coincide with each other. Output to the spinner side. This spinner changes the traveling direction of the combined light beam to the direction toward the inner surface of the inner drum by the uniaxial crystal and the reflecting plate.

  Also, by the action of the quarter wave plate and the uniaxial crystal (Wollaston prism), the synthesized light beam is separated into two light beams at different angles according to the rotation direction of the circularly polarized light. The optical recording medium paper on the inner surface of the drum is scanned with a plurality of light beams by rotating the quarter-wave plate, uniaxial crystal and reflecting plate, which are optical elements, around the central axis by a main scanning motor or the like. However, an apparatus for recording an image has been proposed (for example, see Patent Document 1).

  In such an inner drum type multi-beam exposure system in such an inner drum exposure apparatus, it is desired to be able to switch the resolution of an image recorded on a recording medium. Therefore, in such an inner drum type multi-beam exposure apparatus, in order to be able to switch the resolution of the image, a quarter-wave plate mounted so as to be rotated integrally with the spinner's rotary shaft device, A uniaxial crystal (Wollaston prism) is configured to vary the beam separation width in the sub-scanning direction according to the resolution by rotating and adjusting the incident direction of light with respect to the spinner's rotation axis device. It is possible to do.

However, in the case of such a configuration, if a mechanism for switching resolution is mounted on a spinner rotary shaft device that is required to rotate at an ultra-high speed of tens of thousands of revolutions per minute, the spinner rotary shaft device is Since the size and the weight increase, the rotation speed of the spinner rotating shaft device must be limited to a low value, and the writing speed for scanning and exposing the photosensitive recording medium paper on the inner surface of the drum is low. Arise.
Japanese Patent Laid-Open No. 5-27188

  In view of the above-described problems, the present invention switches the resolution on the optical system from the light source to the spinner mirror device while maintaining the light beam separation width in the sub-scanning direction initially set in the spinner mirror device. It is an object of the present invention to newly provide a resolution switching method in an inner drum type multi-beam exposure system.

  According to the first aspect of the present invention, the resolution switching method in the inner drum type multi-beam exposure system includes the first P-polarized light beam emitted from the first light source and the second light emitted from the second light source. Of the S-polarized light beam, the first and second sets of polarization-coaxial light beams that travel on the same optical path are combined into a third light beam emitted from the third light source. The third and fourth light beams that are coaxially combined with the light beam converted into the P-polarized light and the light beam converted into the fourth S-polarized light emitted from the fourth light source and travel on the same optical path. A pair of polarization coaxial combined light beams, and a first and second set of polarization coaxial combined light beams and a third and fourth set of polarization coaxial combined light beams. A light beam traveling substantially parallel on the road is passed through an imaging optical system for forming an image on the recording medium. On the optical path before being emitted to the spinner mirror device and incident on the spinner mirror device, the first and second sets and the third and fourth sets of the respective coaxial light beams combined with each other are rotated clockwise. The light is converted into circularly polarized light and counterclockwise circularly polarized light, and the right circularly polarized light beam and the left circularly polarized light beam are rotated together with the uniaxial crystal and the reflecting mirror surface installed in the spinner mirror device. Is converted into linearly polarized light orthogonal to each other by a quarter wave plate mounted in such a manner, and then exposed at a predetermined resolution on a recording medium after being reflected by a reflecting mirror surface by a uniaxial crystal placed thereafter Linearly polarized light orthogonal to each other is shifted by one pixel in the sub-scanning direction, and the first and second sets of polarization coaxially combined light beams and the third and fourth sets of polarization coaxially combined are combined. The light travels at least one of the light beams The first deflection image is formed on the recording medium by applying a minute deflection by at least one of the light deflection means for deflecting in the X-axis direction orthogonal to the light deflection means and the light deflection means for deflecting in the Y-axis direction perpendicular to these. A state in which four beams are arranged at equal intervals so as to be shifted by two pixels on the recording medium into a set of the beam spot and the second beam spot, and a set of the third beam spot and the fourth beam spot. This is a method of switching the resolution in the inner drum type multi-beam exposure system of the inner drum exposure apparatus that is imaged to perform scanning exposure, and the exposure processing is performed by switching to a resolution approximately twice the predetermined resolution. Sometimes, in the imaging optical system before being incident on the spinner mirror device, the diameter of the beam spot is changed to correspond to the resolution switched to approximately twice, and the spinner mirror device is side-run. The first moving image is formed on the recording medium by controlling the movement in the scanning direction by the sub-scanning moving means so as to correspond to the resolution switched approximately twice, and applying the minute deflection by the light deflecting means. The beam spot and second beam spot group, and the third beam spot and fourth beam spot group are shifted to each other by an amount corresponding to one pixel after resolution conversion approximately twice on the recording medium. Then, the exposure processing operation is performed such that the third beam spot enters between the first beam spot and the second beam spot, and the fourth beam spot is positioned beside the second beam spot. A method for switching resolution in an inner drum type multi-beam exposure system, characterized in that scanning exposure is performed on a recording medium.

  According to a second aspect of the present invention, the resolution switching method in the inner drum type multi-beam exposure system includes the first P-polarized light beam emitted from the first light source and the second light emitted from the second light source. Of the S-polarized light beam, the first and second sets of polarization-coaxial light beams that travel on the same optical path are combined into a third light beam emitted from the third light source. The third and fourth light beams that are coaxially combined with the light beam converted into the P-polarized light and the light beam converted into the fourth S-polarized light emitted from the fourth light source and travel on the same optical path. A pair of polarization coaxial combined light beams, and a first and second set of polarization coaxial combined light beams and a third and fourth set of polarization coaxial combined light beams. A light beam traveling substantially parallel on the road is passed through an imaging optical system for forming an image on the recording medium. On the optical path before being emitted to the spinner mirror device and incident on the spinner mirror device, the first and second sets and the third and fourth sets of the respective coaxial light beams combined with each other are rotated clockwise. The light is converted into circularly polarized light and counterclockwise circularly polarized light, and the right circularly polarized light beam and the left circularly polarized light beam are rotated together with the uniaxial crystal and the reflecting mirror surface installed in the spinner mirror device. Is converted into linearly polarized light orthogonal to each other by a quarter wave plate mounted in such a manner, and then exposed at a predetermined resolution on a recording medium after being reflected by a reflecting mirror surface by a uniaxial crystal placed thereafter Linearly polarized light orthogonal to each other is shifted by one pixel in the sub-scanning direction, and the first and second sets of polarization coaxially combined light beams and the third and fourth sets of polarization coaxially combined are combined. The light travels at least one of the light beams The first deflection image is formed on the recording medium by applying a minute deflection by at least one of the light deflection means for deflecting in the X-axis direction orthogonal to the light deflection means and the light deflection means for deflecting in the Y-axis direction perpendicular to these. A state in which four beams are arranged at equal intervals so as to be shifted by two pixels on the recording medium into a set of a beam spot and a second beam spot, and a third beam spot and a fourth beam spot set. A method of switching resolution in an inner drum type multi-beam exposure system of an inner drum exposure apparatus that is formed into an image to perform scanning exposure, and when exposure processing is performed by switching to a resolution that is approximately twice a predetermined resolution. Furthermore, in the imaging optical system before entering the spinner mirror device, the diameter of the beam spot is changed to correspond to the resolution switched to approximately twice, and the spinner mirror device is sub-scanned. The first moving image is formed on the recording medium by controlling the movement by the sub-scanning moving means so as to correspond to the resolution switched to approximately double the moving speed in the direction, and adding a minute deflection by the light deflecting means. The beam spot and the second beam spot group, and the third beam spot and the fourth beam spot group are shifted to each other by an amount corresponding to one pixel after resolution conversion of about twice on the recording medium. Thus, when the first exposure is performed, an unexposed portion of one pixel having a resolution approximately doubled is left between the first beam spot and the second beam spot, and the third beam spot and the fourth beam spot are left. Exposure so as to leave an unexposed portion for one pixel of approximately double resolution between the second beam spot and the third beam spot exposed at a position adjacent to the second beam spot, The first exposure The unexposed position between the third beam spot and the fourth beam spot is filled with the first beam spot exposed in the second time, and the fourth beam spot exposed in the first time and the second time exposed. The scanning exposure is performed on the recording medium by repeating the exposure process so that the unexposed position between the third beam spot and the third beam spot is filled with the second beam spot exposed in the second time. A resolution switching method in the inner drum type multi-beam exposure system.

  According to a third aspect of the present invention, there is provided a resolution switching method in the inner drum type multi-beam exposure system according to the first or second aspect, wherein the inner drum exposure apparatus having four multi-beam exposure systems is a predetermined one. When exposure processing is performed while switching to a resolution approximately three times the resolution, the first beam spot and the second beam imaged on the recording medium are applied to the spinner mirror device by applying a minute deflection by the light deflection means. The beam spot group, the third beam spot group, and the fourth beam spot group are shifted from each other by an amount corresponding to two pixels after approximately three times the resolution conversion on the recording medium, and the first exposure is performed. In this case, the third beam spot is exposed at a position adjacent to the second beam spot between the first beam spot and the second beam spot. Repeating the exposure process so that the unexposed position between the second beam spot exposed at the first time and the fourth beam spot is filled with the first beam spot exposed at the second time. 3. The method of switching resolution in an inner drum type multi-beam exposure system according to claim 1, wherein scanning exposure is performed on the recording medium.

  According to the inner drum type multi-beam exposure method described above, when the resolution is changed by the inner drum exposure device, the diameter of the beam spot is changed corresponding to each resolution, and the spinner mirror device is moved in the sub-scanning direction. The exposure processing is performed by controlling the movement by the sub-scanning moving means so as to correspond to each resolution, and the light deflecting means for deflecting in the X-axis direction orthogonal to the light traveling direction, and in the Y-axis direction orthogonal thereto. A small deflection is applied by controlling at least one of the deflecting light deflecting means, and between the set of the first beam spot and the second beam spot, and the set of the third beam spot and the fourth beam spot. Then, scanning exposure is performed on the recording medium by performing an exposure process by shifting the relative position. Therefore, since it is possible to switch the resolution without installing a mechanism for switching the resolution on the rotating shaft device of the spinner mirror device, the rotating shaft device of the spinner increases in size and weight, and the spinner rotating shaft device rotates. The high-speed exposure process using four multi-beams is enabled while avoiding the necessity of limiting the speed to be low.

  According to the resolution switching method in the inner drum type multi-beam exposure system of the present invention, the auxiliary shaft initially set in the spinner mirror device is installed without attaching a mechanism for switching the resolution to the rotary shaft device or the like of the spinner mirror device. There is an effect of enabling high-speed exposure processing by switching the resolution on the optical system from the light source to the spinner mirror device while maintaining the beam separation width in the scanning direction.

  A first embodiment relating to an inner drum exposure apparatus capable of performing a resolution switching method in an inner drum type multi-beam exposure system will be described with reference to FIG. As shown in the schematic configuration diagram of FIG. 1, the inner drum exposure apparatus 10 is configured with a support 12 having an arc inner peripheral surface shape (a shape constituting a part of a cylindrical inner peripheral surface) as a base, and this support. A recording medium 14 (a photopolymer plate, a normal PS plate, or a silver salt type photosensitive material) is supported along the inner peripheral surface of the body 12.

  In this inner drum exposure apparatus 10, an unrecorded recording medium 14 is supplied by a supply / discharge device for a recording medium 14 (not shown), and is securely attached to the inner peripheral surface of the support 12 and is attached. After that, an exposure process is performed, and an operation for discharging the exposed recording medium 14 from the support 12 to the outside is performed.

  In the inner drum exposure device 10, a spinner mirror device 16 as a scanning means (light deflector) is disposed at the center of the arc of the support 12. The spinner mirror device 16 includes a columnar rotary shaft member 18 that can be rotated by a motor 20 that is a drive source with a central axis thereof as a rotary axis (corresponding to the arc central axis of the support 12).

  A reflecting mirror surface 18A that forms an angle of 45 ° with respect to the rotational axis is formed at the tip of the rotational shaft member 18 of the spinner mirror device 16 that is this optical deflector. The spinner mirror device 16 as scanning means is controlled to move in the axial direction of the arc central axis of the support 12 (in the direction of arrow C in FIG. 1) in accordance with the resolution by a sub-scanning movement means (not shown). In the spinner mirror device 16, the rotation of the motor 20 is controlled by a spinner driver 22 controlled by the central control device 21.

  As shown in FIG. 1, in the inner drum exposure apparatus 10, a light source that projects a multi-beam (a plurality of light beams) to the spinner mirror device 16 side in order to perform main scanning on the recording surface of the recording medium 14 by a multi-beam method. Side optical system is provided.

  The optical system on the light source side includes first and second semiconductor laser light sources (LD) 30A and 30B (light beam output means) for modulating and outputting the light amounts of laser beams La and Lb made of substantially linearly polarized light, and A condensing optical system for condensing the laser beams La and Lb respectively emitted from the first and second semiconductor laser light sources 30A and 30B on the exposure surface of the recording medium 14; As these first and second semiconductor laser light sources 30A and 30B, single transverse mode semiconductor lasers having an intensity distribution in which the center light intensity is high and the light intensity gradually decreases as the distance from the center is increased are used. it can.

  The inner drum exposure apparatus 10 is configured to perform main scanning on the recording surface of the recording medium 14 arranged on the inner peripheral surface of the support 12 by performing beam splitting.

  For this reason, on the spinner mirror device 16 side, a quarter wavelength plate 26 and a uniaxial crystal optical element 28 are sequentially attached to a holder 24 fixed so as to rotate integrally with the rotary shaft member 18 from the upstream side of the optical path. And fix them. The quarter-wave plate 26 and the uniaxial crystal optical element 28 may be overlapped and integrally bonded with a transparent adhesive for the optical element.

  Here, the optical element 28 of the uniaxial crystal is, for example, when a circularly polarized light beam is incident thereon, as shown in FIG. 5, the light beam is equal in intensity to the ordinary ray Po and the extraordinary ray Pe. The light beam is separated and the ordinary light Po and the extraordinary light Pe are shifted in parallel with each other.

  As shown in FIG. 1, the holder 24 is formed in a cylindrical shape, for example, and is formed by drilling an opening for allowing the light beam reflected by the reflecting mirror surface 18A to pass to the recording medium 14 side.

  The quarter-wave plate 26 and the uniaxial crystal optical element 28 are arranged in the optical path in front of the reflecting mirror surface 18A in the spinner mirror device 16, and are integrated with the reflecting mirror surface 18A by a separately provided support means (not shown). It may be configured to be mounted so as to rotate.

  The quarter-wave plate 26 is configured to be capable of converting the right circularly polarized light and the left circularly polarized light beam into linearly polarized light beams orthogonal to each other.

  The uniaxial crystal optical element 28, for example, parallelly shifts one polarized beam of two mutually orthogonal linearly polarized beams in the sub scanning direction (emits two linearly polarized light beams in parallel from different positions, respectively). ) Consists of a quartz plate. As shown in FIG. 5, the uniaxial crystal optical element 28, which is a quartz plate, is manufactured to have a structure in which the crystal optical axis of the quartz is inclined by 45 ° with respect to the normal line of the light crystal incident surface. .

  Here, when the accuracy of the separation interval is set to ± 0.1 μm, the thickness accuracy may be set to about ± 18 μm, so that this quartz plate can be easily processed to have sufficient accuracy, It can be manufactured at low cost. Furthermore, quartz used as a material for the uniaxial crystal optical element 28 has the advantage of being stable in material and low in cost. Further, since the crystal used as the material of the uniaxial crystal optical element 28 has a split width characteristic with respect to the tilt angle of the crystal optical axis shown in FIG. 3, the uniaxial characteristic having a required function in accordance with the crystal characteristic. A crystal optical element 28 can be formed.

  The uniaxial crystal optical element 28 may be made of a uniaxial crystal other than quartz.

  The uniaxial crystal optical element 28 may be formed using a uniaxial material such as calcite or lithium niobate. Here, when calcite is used, since the thickness can be reduced, there is an advantage that the weight can be suppressed and the limitation on the rotation speed of the spinner mirror device 16 can be suppressed. In this case, the quarter-wave plate 26 and the uniaxial crystal optical element 28 made of calcite may be adhered and used.

  In the inner drum exposure apparatus 10 according to the first embodiment, for example, the resolution is reduced from 2400 dpi to 2438 dpi, 2540 dpi, and the like in a range of about 10% according to the user's purpose of use. It is configured so that it can be switched and used so that the commercial value of the inner drum exposure apparatus 10 can be improved.

  This inner drum exposure apparatus 10 is configured to enable high-speed exposure processing by switching the resolution while maintaining the initially set beam separation width in the sub-scanning direction in the two multi-beam exposure systems. For this reason, in this inner drum exposure apparatus 10, the two laser beams La and Lb separated and emitted by the optical element 28 of the uniaxial crystal are reflected by the spinner mirror device 16 that is an optical deflector and reflected on the recording medium 14. Two laser beams La and Lb are focused on a scanning surface at a position separated by a predetermined interval corresponding to one recording pixel in the sub-scanning direction.

  Further, in the inner drum exposure apparatus 10 equipped with the two multi-beam exposure systems, a predetermined interval corresponding to one recording pixel in the sub-scanning direction is separated on the scanning surface of the recording medium 14 even when the resolution is switched. The two laser beams La and Lb are condensed at the positions so that the scanning unevenness appearing in the image subjected to the exposure process is within an allowable range.

  Therefore, in the inner drum exposure apparatus 10, the distance between the spots a and b by the laser beams La and Lb separated on the scanning surface by the optical element 28 of the uniaxial crystal attached to the spinner mirror device 16 is set so that the unevenness cannot be seen. Set up and configure.

  Therefore, for example, the interval between the first beam spots a and b corresponding to the first resolution to be switched is D1, and the interval between the second beam spots a and b corresponding to the second resolution to be switched is D2. And when the design tolerance in the sub-scanning direction is D4, the uniaxial crystal optical element 28 separates the laser beams La and Lb and is focused on the scanning surface. Is set in accordance with the equation D3 = (D1 + D2) / 2 ± D4.

  In this inner drum exposure apparatus 10, for example, the interval between the beam spots a and b when the resolution is 2400 dpi is 10.6 μm, and the interval between the beam spots a and b when the resolution is 2540 dpi after switching is 10 μm. The interval between the beam spots a and b that are separated and collected by the optical element 28 of the uniaxial crystal is set in the vicinity of 10.3 μm, which is the center of the interval between the beam spots a and b at each resolution.

  That is, in the inner drum exposure apparatus 10, the beam separation width on the scanning surface by the optical element 28 of the uniaxial crystal is set to 10.3 μm ± 0.3 μm so as to correspond to the user's purpose of use. For example, the resolution can be switched from a range of 2400 dpi to 2438 dpi, further to 2540 dpi, and the like within a range of about 10%.

  In the inner drum exposure apparatus 10 having such two multi-beam exposure systems, the scanning unevenness of the formed image is within an allowable range even if the beam separation width on the scanning surface has a gap error of up to about 1 μm. Therefore, if the design center value of the beam separation width on the scanning plane by the uniaxial crystal optical element 28 is set to 10.3 μm, the production error of the separation width, Even if there are vibrations in the scanning direction, changes in feed speed, etc., it is possible to optimally form an image.

Further, in the inner drum exposure apparatus 10 including the two multi-beam exposure systems, for example, 2400 dpi (2R ₀ dpi) that uses the resolution most frequently for the exposure processing is set as a standard. For example, when recording is performed with the inner drum exposure apparatus 10 changing the resolution from 2400 dpi (2R ₀ dpi) to 1200 dpi (R ₀ dpi), the exposure processing is performed at a resolution of 2400 dpi (2R ₀ dpi). This can be handled by exposing the same image information with two laser beams La and Lb separated by the optical element 28 of uniaxial crystal. The resolution may be set to 4800 dpi (2R ₀ dpi) as a standard, and the resolution may be changed from 4800 dpi (2R ₀ dpi) to 2400 dpi (R ₀ dpi) for recording.

  In the inner drum exposure apparatus 10 described above, the uniaxial crystal optical element 28 has been described as separating the two laser beams La and Lb so that they are emitted in parallel. As shown in FIG. 6, a single prism-shaped quartz plate 250 may be used to emit and separate the two laser beams La and Lb in different angular directions.

  This prism-shaped quartz plate 250 uses two quartz crystals formed in a prism shape having a smaller refractive index anisotropy than calcite, and is formed by suppressing the apex angle of the prism to be small, so that two mutually orthogonal straight lines are formed. When the polarized laser beams La and Lb are transmitted, the laser beams La and Lb are emitted in different predetermined angular directions, and the beam spots a and b focused on the scanning surface are set at desired intervals. Configure to

  That is, the prism-shaped quartz plate 250 has an axis having a high phase velocity and a slow axis in one surface, and the other surface is arranged with respect to an axis having a high phase velocity and a slow axis on one surface. Configure to tilt.

  In the inner drum exposure apparatus using the prism-shaped quartz plate 250, although not shown, the light beams a and b emitted at a predetermined angle so as to be separated from the prism-shaped quartz plate 250 are emitted. The two laser beams La and Lb are condensed and exposed at a position reflected by the optical deflector and separated by a predetermined interval of one recording pixel in the sub-scanning direction on the scanning surface.

  As shown in FIG. 1, the inner drum exposure device 10 projects a light beam from the light source side toward the spinner mirror device 16 side in order to perform main scanning on the recording surface of the recording medium 14 by separating the light beam. An optical system is provided.

  In this inner drum exposure apparatus, first and second semiconductor laser light sources 30A and 30B (light beam output means) are used. That is, since the first and second semiconductor laser light sources 30A and 30B respectively emit linearly polarized light beams (laser beams) La and Lb, both the light beams La and Lb are respectively collimated lenses (collimator lenses). ) 32 and 34 are respectively parallel beams.

  The first laser beam La emitted from the first semiconductor laser light source 30A is set to be P-polarized with respect to the reflection surface of the polarization beam splitter 38, and after passing through the parallel plate 36, the polarization beam splitter 38. Proceed through.

  Further, the second laser beam Lb passes through the two angle adjusting prisms 40 and 42 and then passes through the half-wave plate 44 so that the polarization direction is rotated by 90 ° and reflected by the polarization beam splitter. The light enters the polarization beam splitter 38 after being S-polarized with respect to the surface. Then, the second laser beam Lb becomes S-polarized light, is reflected by the reflecting surface of the polarization beam splitter 38, is coaxially combined with the first laser beam La, and travels on the same optical path to the spinner mirror device 16. .

  In the optical system on the light source side of the inner drum exposure apparatus 10, it is necessary to correct with high accuracy the amount of deviation over time, including during assembly adjustment. This is because the beam spots a and b on the scanning surface correspond to the rotation angle of the optical deflector unless the coaxial multiplexing of the first laser beam La and the second laser beam Lb is performed with high accuracy. This is because the problem that the position interval fluctuates occurs.

  Therefore, in the optical system on the light source side, a PSD (beam position detector) 46 is installed on the optical path downstream of the polarization beam splitter 38. For this reason, a beam splitter 48 is installed at a predetermined position on the optical path downstream from the polarizing beam splitter 38, thereby reflecting part of the light of the first laser beam La and the second laser beam Lb. Then, the light is condensed on a PSD (beam position detector) 46 installed at a position corresponding to the scanning surface by the condensing lens 50, and the first laser beam La and the second laser beam Lb on the scanning surface. Configure the position to be detectable.

  Here, the deviation of the beam spot position on the scanning plane requires a resolution of about 0.1 μm or less from the viewpoint of suppressing unevenness in image quality, and therefore, taking the detection resolution of the PSD (beam position detector) 46 into consideration, the PSD It is desirable that the beam spot position change is enlarged 10 times or more.

  When the beam position is detected by the PSD (beam position detector) 46, the first laser beam La and the second laser beam Lb are separately provided when exposure recording is not performed on the recording medium. Are lit with a predetermined amount of light and detected individually. The PSD (beam position detector) 46 detects the position of the PSD (beam) so that the position information is not shifted due to the light quantity difference between the two first laser beams La and the second laser beam Lb. In the circuit board of the position detector 46, a circuit for dividing by the total light quantity or a circuit for correcting by calculation after data acquisition is provided.

  In the inner drum exposure apparatus 10, the first laser beam La and the second laser beam are based on position information detected by a PSD (beam position detector) 46 when exposure recording is not performed on the recording medium. The angles of the two angle adjusting prisms 40 and 42 placed on the optical path of the second laser beam Lb are adjusted so that the positional deviation from Lb is 0 or a position away from the predetermined value.

  Note that the predetermined value, which is the amount of positional deviation between the first laser beam La and the second laser beam Lb, is preliminarily exposed to the recording medium before shipping of the inner drum exposure apparatus 10 and is two in the main scanning direction. A place where there is no fluctuation in the beam interval of the book is obtained and set.

  In addition, the predetermined value may not be 0 when the first laser beam La and the second laser beam Lb are slightly shifted in parallel, especially when they are reflected by the reflecting mirror. This is because the reflection angle between the first laser beam La and the second laser beam Lb may be slightly shifted according to the above. That is, in this inner drum exposure apparatus 10, there are different angular deviations between the optical path after the second laser beam Lb is reflected by the polarization beam splitter 38 and the optical path after the first laser beam La is transmitted. This will occur and this needs to be corrected. Therefore, in the inner drum exposure apparatus 10, the first laser beam La and the second laser beam La are adjusted by adjusting the inclination angle by the parallel plate 36 disposed on the optical path of the first laser beam La during assembly adjustment. The amount of parallel shift with the laser beam Lb is adjusted to approach zero.

  The first laser beam La and the second laser beam Lb, which are coaxially combined with high accuracy as described above, are subjected to beam shaping and astigmatism correction by a cylinder lens group (not shown) arranged on the optical path. Further, after being expanded to a desired beam diameter by a beam expander, it passes through a quarter-wave plate 52 arranged on the optical path.

  The quarter-wave plate 52 has an optical axis inclined by 45 ° with respect to the direction of linear polarization of the first laser beam La and the second laser beam Lb. For this reason, the coaxially combined first laser beam La and second laser beam Lb passing through the quarter-wave plate 52 are converted into right circularly polarized light and left circularly polarized light, respectively, and are focused on the scanning plane. Through the condensing lens 54 for linking, the light advances substantially parallel to the rotational axis of the reflecting mirror surface 18A of the spinner mirror device 16 and is guided to the spinner mirror device 16 of the scanning optical system described above.

  The first laser beam La and the second laser beam Lb that are right-circularly polarized light and left-circularly polarized light incident on the spinner mirror device 16 of the scanning optical system from the optical system on the light source side are the same as those of the spinner mirror device 16. The light is converted into linearly polarized beams orthogonal to each other by passing through a quarter-wave plate 26 installed on the rotation shaft 18 and then incident on an optical element 28 of a uniaxial crystal.

  The first laser beam La and the second laser beam Lb thus converted into mutually orthogonal linearly polarized beams are transmitted in the sub-scanning direction when passing through the optical element 28 of the uniaxial crystal of the scanning optical system. After the parallel shift, the light is reflected by the reflecting mirror surface 18A of the optical deflector and condensed on the scanning surface of the recording medium 14 at a position separated by a predetermined distance corresponding to one recording pixel in the sub-scanning direction.

  In the inner drum exposure apparatus 10, a laser driver 23 for the first semiconductor laser light source 30A and a laser driver 25 for the second semiconductor laser light source 30B are provided, and each image signal separately generated by the central controller 21 is provided. The first laser beam La transmitted to the respective laser drivers 23 and 25 to drive and control the first semiconductor laser light source 30A and the second semiconductor laser light source 30B, respectively, and modulated based on the corresponding image signals, The second laser beam Lb is emitted and irradiated onto the scanning surface of the recording medium 14 by the optical system on the light source side and the spinner mirror device 16 of the scanning optical system.

  At the same time, the central controller 21 transmits a control signal to the spinner driver 22 as described above to control the rotation of the motor 20 to rotate the reflecting mirror surface 18A, and from the optical system on the light source side to the scanning optical system. The first laser beam La and the second laser beam Lb incident on the reflecting mirror surface 18A are reflected, and the recording medium 14 is subjected to scanning exposure in the main scanning direction. At the same time, the central control device 21 transmits a control signal to the spinner driver 22. Upon receiving this control signal, the spinner driver 22 controls the sub-scanning moving means (not shown), and the spinner mirror device 16 is moved in the axial direction of the center axis of the arc of the support 12 (arrows in the left-right direction toward FIG. 1). Move and scan in the C direction) at a constant speed. Thus, a two-dimensional image is recorded on the entire recording surface of the recording medium 14 by moving the spinner mirror device 16 in the sub-scanning direction while performing scanning exposure in the main scanning direction by the spinner mirror device 16. Configure to perform processing.

  Next, the operation and operation of the inner drum exposure apparatus according to the first embodiment will be described.

  In the inner drum exposure apparatus 10, a first laser beam La modulated and output according to image information from a first semiconductor laser light source 30 </ b> A controlled by a central controller and a laser driver is converted into a collimating lens (collimating lens). After being converted into a parallel beam by the meter lens 32 and transmitted through the parallel flat plate 36, the light is incident on the polarization beam splitter 38. At this time, since the first laser beam La is P-polarized with respect to the reflection surface of the polarization beam splitter 38, the first laser beam La travels through the polarization beam splitter 38.

  The second laser beam Lb modulated and output according to image information from the second semiconductor laser light source 30B is converted into a parallel beam by a collimating lens (collimator lens) 34, and is used for two angle adjustments. After passing through the prisms 40 and 42, the polarization direction is rotated by 90 ° by passing through the half-wave plate 44, so that it becomes S-polarized light and then enters the polarization beam splitter 38.

  Then, the second laser beam Lb becomes S-polarized light, is reflected by the reflecting surface of the polarization beam splitter 38, is coaxially combined with the first laser beam La, and travels on the same optical path to the spinner mirror device 16. .

  The first laser beam La and the second laser beam Lb thus coaxially combined pass through the quarter-wave plate 52 and are converted into right circularly polarized light and left circularly polarized light, respectively, on the scanning plane. The light passes through a condenser lens 54 for focusing, and is guided to a spinner mirror device 16 of a scanning optical system including a quarter-wave plate 26 and a uniaxial crystal optical element 28.

  The first laser beam La and the second laser beam Lb converted to right circularly polarized light and left circularly polarized light are linearly polarized light orthogonal to each other when passing through the quarter wavelength plate 26 of the scanning optical system. After being converted into a light beam and incident on the optical element 28 of a uniaxial crystal and separated so that two mutually orthogonal linearly polarized beams are parallel-shifted in the sub-scanning direction, along the rotation axis of the spinner mirror device 16 Introduced, reflected and deflected by the reflecting mirror surface 18 </ b> A and guided to the recording medium 14.

  In the inner drum exposure apparatus having two multi-beam exposure systems according to the first embodiment, for example, 2400 dpi is set to a standard resolution, and the resolution is changed from 2400 dpi to 1200 dpi with the inner drum exposure apparatus 10. The same image information is exposed with the two laser beams La and Lb when recording is performed by changing to the above. Furthermore, the speed at which the spinner mirror device 16 is moved in the sub-scanning direction in accordance with the resolution is changed and adjusted so as to match the resolution at that time.

  Next, a second embodiment relating to an inner drum exposure apparatus capable of performing the resolution switching method in the inner drum type multi-beam exposure system of the present invention will be described with reference to FIGS. In the second embodiment, the inner drum exposure apparatus 10 is configured to perform main scanning on the recording surface of the recording medium 14 disposed on the inner peripheral surface of the support with four light beams.

  In this spinner mirror device 16, a quarter-wave plate 226 and a uniaxial crystal optical element 228 are fixed in order from the upstream side of the optical path to a holder 24 fixed so as to rotate integrally with the rotary shaft member 18. And place it.

  The quarter-wave plate 226 and the uniaxial crystal optical element 228 are disposed in the optical path in front of the reflecting mirror surface 18A in the spinner mirror device 16, and are integrated with the reflecting mirror surface 18A by a separately provided support means (not shown). It may be configured to be mounted so as to rotate.

  The quarter-wave plate 226 is configured to be able to convert each of the right and left circularly polarized light beams into linearly polarized light beams orthogonal to each other.

  The uniaxial crystal optical element 228 is equivalent to the optical element 228 illustrated in FIG. 5 described above, and is composed of a quartz plate that shifts two mutually orthogonal linearly polarized beams in parallel in the sub-scanning direction. This quartz plate is manufactured to have a structure in which the crystal optical axis of the quartz is inclined by 45 ° with respect to the normal line of the light crystal incidence surface.

  The uniaxial crystal optical element 228 may be configured to emit and separate each laser beam in different angular directions using one prism-shaped quartz plate 250 shown in FIG. 6 described above. good.

  The inner drum exposure apparatus 10 according to the second embodiment enables high-speed exposure processing by switching the resolution while maintaining the initially set beam separation width in the sub-scanning direction in the four multi-beam exposure systems. Constitute. For this reason, in this inner drum exposure apparatus 10, the laser beams La, Lb, Lc, and Ld, which are a total of four beams of two groups and two beams separated and emitted by the optical element 28 of the uniaxial crystal, are optical deflectors. Four laser beams La, Lb, Lc, which are reflected by a certain spinner mirror device 16 and are spaced apart from each other at a predetermined interval corresponding to one recording pixel in the sub-scanning direction on the scanning surface of the recording medium 14. Ld is condensed and exposed.

  Further, in the inner drum exposure apparatus 10 having the four multi-beam exposure systems, a predetermined number corresponding to one recording pixel in the sub-scanning direction on the scanning surface of the recording medium 14 even when the resolution is switched. The four laser beams La, Lb, Lc, and Ld are condensed at respective positions spaced apart from each other so that the scanning unevenness that appears in the image subjected to the exposure process is within an allowable range.

  Therefore, in the inner drum exposure apparatus 10, the distance between the spots a and b by the laser beams La and Lb separated on the scanning plane by the uniaxial crystal optical element 28 attached to the spinner mirror device 16, and the laser beam Lc, The interval between the spots c and d by Ld is set to an interval at which no unevenness is visible. Note that the interval between the spot a by the laser beam La and the spot c by the laser beam Lc is set to a predetermined interval in which unevenness is not visible by controlling the acoustooptic device 116 and the acoustooptic device 118 described above.

  For this reason, for example, the scanning line interval corresponding to the first resolution to be switched is D1, the scanning line interval corresponding to the second resolution to be switched is D2, and the design allowable error in the sub-scanning direction. Is D4, the optical element 28 of the uniaxial crystal separates the set of the laser beams La and Lb and the set of the laser beams Lc and Ld, and collects the beam spots a, A setting interval D3 in the sub-scanning direction between the set of b and the set of beam spots c and d is obtained and set by the formula D3 = (D1 + D2) / 2 ± D4. Note that the set interval D3 has a problem with the interval when scanning is performed with the set of beam spots a and b and the set of beam spots c and d on the scanning plane. Even when it is positioned obliquely with respect to the sub-scanning direction on the scanning surface, the distance component in the sub-scanning direction is set as the set interval D3.

  In this inner drum exposure apparatus 10, for example, when the interval between scanning lines at a resolution of 1200 dpi is 21.2 μm and the interval between scanning lines at a resolution of 1270 dpi after switching is 20.0 μm, the uniaxial crystal The distance between the beam spots a and b that are separated and condensed by the optical element 28 and the distance between the beam spots c and d are set in the vicinity of 20.6 μm. That is, the beam separation width on the scanning surface by the uniaxial crystal optical element 28 is set to 20.6 μm ± 0.2 μm.

  In the inner drum exposure apparatus 10 having such four multi-beam exposure systems, the scanning unevenness of the formed image is within an allowable range even if there is a gap error of about 1 μm in the beam separation width on the scanning surface. Therefore, if the design center value of the beam separation width on the scanning plane by the uniaxial crystal optical element 28 is set to 20.6 μm, the production error of the separation width, Even if there are vibrations in the scanning direction, changes in feed speed, etc., it is possible to optimally form an image.

  As shown in FIG. 2, the inner drum exposure apparatus 10 separates the combined light beam and performs main scanning on the recording surface of the recording medium 14, so that the light beam to be incident on the spinner mirror device 16 is used. An optical system on the light source side for projection is provided.

  The inner drum exposure apparatus 10 uses first, second, third, and fourth semiconductor laser light sources 230A, 230B, 230C, and 230D (light beam output means). Further, the first and second semiconductor laser light sources 230A and 230B and the third and fourth semiconductor laser light sources 230C and 230D are configured as separate sets of optical systems.

  The set of the first and second semiconductor laser light sources 230A and 230B respectively emit linearly polarized light beams (laser beams) La and Lb. In these sets of optical systems, both light beams La and Lb are collimated by collimating lenses (collimator lenses) 232 and 234, respectively.

  The first laser beam La emitted from the first semiconductor laser light source 230A is set to be P-polarized with respect to the reflection surface of the polarization beam splitter 238, and after passing through the parallel plate 236, the polarization beam splitter 238. Through the light path.

  The second laser beam Lb is transmitted through the half-wave plate 244 so that the polarization direction is rotated by 90 ° to become S-polarized light, and then enters the polarization beam splitter 238. Then, the second laser beam Lb becomes S-polarized light and is reflected by the reflection surface of the polarization beam splitter 238, and is polarized and coaxially combined with the first laser beam La and travels on the same optical path.

  The first laser beam La and the second laser beam Lb emitted from the polarization beam splitter 238 and combined with each other in the same axis are combined with the second condenser lens 102, the partial optical function member 104, and the second laser beam Lb. The light is incident on the spinner mirror device 16 through an optical path of an optical system configured by sequentially arranging the third condenser lens 106, the quarter wavelength plate 107, and the fourth condenser lens 108.

  The partial optical function member 104 includes a light beam emitted from the first and second semiconductor laser light sources 230A and 230B and combined by polarization and coaxial, and third and fourth semiconductor laser light sources to be described later. The light beams emitted from one of the laser light sources in the light beams emitted from 230C and 230D and polarized and coaxially combined are transmitted to the spinner mirror device 16 and transmitted to the spinner mirror device 16, and the other laser The light beam emitted from the set of light sources and polarized and coaxially combined is reflected so as to be guided to the spinner mirror device 16 by the same optical system.

  That is, as shown in FIGS. 2 and 3, the partial optical functional member 104 transmits (passes) the light beam emitted from the first and second semiconductor laser light sources 230A and 230B and combined with the polarization coaxially. ) To the spinner mirror device 16, and to the spinner mirror device 16 by reflecting the light beams emitted from the third and fourth semiconductor laser light sources 230C and 230D and polarized and coaxially combined. Constitute.

  For this reason, the partial optical functional member 104 has a circular transparent shape when viewed from the front in a tilted state at a predetermined angle as the transmitting portion 110 that allows the laser beam La emitted from the first semiconductor laser light source 30A to pass through the central portion thereof. Forming part. At the same time, the partial optical function member 104 is configured such that the entire surface excluding the transmission part 110 (or a predetermined range around the transmission part 110) may be formed as the reflection part (reflection surface) 111. The partial optical functional member 104 shown in FIGS. 1 to 3 is formed of a transparent glass plate as a whole, and is formed by processing the entire surface except the central transmission portion 110 into a mirror surface. Configuration can be taken. Further, the transmission part 110 may be formed in the opening.

  Further, the partial optical function member 104 is arranged such that the transmission part 110 becomes the imaging position of the second condenser lens 102 and the reflection part 111 becomes the imaging position of the second condenser lens 120.

  The partial optical function member 104 may be composed of a composite member that is an optical member that reflects at least part of one light beam and transmits at least part of the other light beam, such as a half mirror. Moreover, when using a half mirror, it is not necessary to use the condensing lens for condensing on a partial optical function member.

  The pair of the third and fourth semiconductor laser light sources 230C and 230D emit linearly polarized light beams (laser beams) Lc and Ld, respectively. In these sets of optical systems, both light beams Lc and Ld are collimated by collimating lenses (collimator lenses) 232 and 234, respectively.

  The third laser beam Lc emitted from the third semiconductor laser light source 230C is set to be P-polarized with respect to the reflection surface of the polarization beam splitter 238, and after passing through the parallel plate 236, the polarization beam splitter 238. Through the light path.

  The fourth laser beam Ld is transmitted through the half-wave plate 244 so that the polarization direction is rotated by 90 ° to become S-polarized light, and then enters the polarizing beam splitter 238. Then, the fourth laser beam Ld becomes S-polarized light, is reflected by the reflecting surface of the polarization beam splitter 238, is combined with the third laser beam Lc and is coaxially polarized, and is emitted from the polarization beam splitter 238 to be the same light. Go on the street.

  The third laser beam Lc and the fourth laser beam Ld, which are emitted from the polarization beam splitter 238 and are coaxially combined with each other, are deflected in the X-axis direction with respect to the reflecting mirror 114 and the spinner mirror device. An acoustooptic element 116 that is an optical deflecting means, an acoustooptic element 118 that is an optical deflecting means that deflects in the Y-axis direction, a second condensing lens 120, a shared partial optical function member 104, and a third condensing element. The light enters the spinner mirror device 16 through an optical path formed by sequentially arranging the lens 106, the quarter-wave plate 107, and the fourth condenser lens 108.

  These acousto-optic elements 116 and acousto-optic elements 118 which are light deflecting means are controlled by the circuit shown in FIG. The circuit as the control means includes a control circuit 122 that generates a control clock signal based on a signal from an encoder (not shown) provided in the spinner mirror device 16, and a cosine wave signal that generates a cosine wave voltage signal according to the control clock signal. A generation circuit 124, a sine wave signal generation circuit 126 that generates a sine wave voltage signal according to the control clock signal, a voltage controlled oscillator 128 that generates a frequency modulation signal from the cosine wave voltage signal, and a frequency from the sine wave voltage signal A voltage-controlled oscillator 130 that generates a modulation signal, an amplifier 132 that amplifies the frequency-modulated signal from the voltage-controlled oscillator 128 and supplies it to the acoustooptic device 116, and a voltage-controlled oscillator 130 that generates a frequency-modulated signal from a sine wave signal Amplifier 1 that amplifies the frequency modulation signal from the signal and supplies it to the acoustooptic device 118 And a 4.

  In the second embodiment described above, the acoustooptic element 116 and the acoustooptic element 118, which are light deflecting means, are configured separately. It is also possible to configure the optical deflecting means so as to realize deflection in the X-axis and Y-axis directions. Further, instead of using an acousto-optic element, an electro-optic element or the like may be used.

  In the optical system on the set side of the third and fourth semiconductor laser light sources 230C and 230D configured as described above, polarization coaxial multiplexing is performed from the third and fourth semiconductor laser light sources 230C and 230D and output. The light beam is deflected by the acoustooptic element 116 and the acoustooptic element 118 which are light deflecting means controlled by the control means, and the light beam is deflected by the second condenser lens 120 by the reflecting portion 111 of the partial optical function member 104. Then, the light is emitted from the first and second semiconductor laser light sources 230A and 230B by the third condenser lens 106 and converted into parallel light with respect to the light beam that has undergone polarization coaxial multiplexing. The beam is condensed by the optical lens 108 and reflected by the reflecting mirror surface 18A of the spinner mirror device 16, and formed on the recording medium 14 to perform scanning exposure.

  When performing this scanning exposure, in the inner drum exposure apparatus 10, a circuit as a control means (not shown) controls and deflects the acousto-optic element 116 and the acousto-optic element 118, which are light deflecting means. Scanning exposure is appropriately performed in the main scanning direction by linking the light beam that is output from the fourth semiconductor laser light sources 230C and 230D by being subjected to the coaxial coaxial multiplexing with the operation of the spinner mirror device 16.

  For this reason, a control circuit (not shown) as a control means supplies a control clock signal to the cosine wave signal generation circuit 124 shown in FIG. 8 based on a position signal from an encoder (not shown) provided in the spinner mirror device 16. The cosine wave voltage signal output from the cosine wave signal generation circuit 124 is converted into a frequency modulation signal by the voltage control oscillator 128 and then supplied to the acoustooptic device 116 via the amplifier 132. In this case, the acousto-optic device 116 converts the light beam output by polarization coaxial multiplexing from the third and fourth semiconductor laser light sources 230C and 230D based on this cosine wave voltage signal in the X-axis direction (reflecting mirror surface 18A). (Inclination direction passing through the center).

  The control circuit as the control means supplies a control clock signal to the sine wave signal generation circuit 126. The sine wave voltage signal output from the sine wave signal generation circuit 126 is converted into a frequency modulation signal by the voltage controlled oscillator 130 and then supplied to the acoustooptic device 118 via the amplifier 134. In this case, the acoustooptic device 118 converts the second laser beam Lb modulated in the X axis direction by the acoustooptic device 116 based on the sine wave voltage signal into the Y axis direction (reflecting mirror surface 18A) based on the sine wave voltage signal. In a direction perpendicular to the inclination direction passing through the center of the head.

  As a result, the light beams output by being subjected to polarization coaxial multiplexing from the third and fourth semiconductor laser light sources 230C and 230D guided to the reflecting mirror surface 18A of the spinner mirror device 16 are output from the quarter-wave plates 107 and 1. In a state separated by the action of the quarter-wave plate 226 and the optical element 228 of the uniaxial crystal, it is orthogonal to the rotation axis 18 of the spinner mirror device 16 as shown in FIG. A substantially circular locus is drawn on the surface S 'to be performed.

  Next, the operation and operation of the inner drum exposure apparatus 10 according to the second embodiment configured as described above will be described.

  In the inner drum exposure apparatus 10 according to the second embodiment, the first laser is light-modulated and output in accordance with image information from a first semiconductor laser light source 230A controlled by a central controller (not shown) and a laser driver. The beam La is converted into a parallel beam by a collimating lens (collimator lens) 232, transmitted through a parallel plate 236, and then incident on a polarization beam splitter 238. At this time, since the first laser beam La is P-polarized with respect to the reflection surface of the polarization beam splitter 238, it travels through the polarization beam splitter 238.

  In addition, the second laser beam Lb, which is modulated and output in accordance with the image information from the second semiconductor laser light source 230B, is converted into a parallel beam by a collimating lens (collimator lens) 234, and a half-wave plate By passing through 244, the polarization direction is rotated by 90 ° to become S-polarized light, and then enters the polarizing beam splitter 238.

  Then, the second laser beam Lb becomes S-polarized light and is reflected by the reflection surface of the polarization beam splitter 238, and is polarized and coaxially combined with the first laser beam La. Passes through the quarter wavelength plate 107 through the transmission part 110 of the objective optical function member 104 and the third condenser lens 106. The first laser beam La and the second laser beam Lb, which are combined by the coaxial polarization, are converted into right circularly polarized light and left circularly polarized light when passing through the quarter wavelength plate 107, and are focused on the scanning plane. And is guided to a spinner mirror device 16 of a scanning optical system including a quarter-wave plate 226 and a uniaxial crystal optical element 228.

  The first laser beam La and the second laser beam Lb converted into right circularly polarized light and left circularly polarized light are linearly polarized light orthogonal to each other when passing through the quarter wavelength plate 226 of the scanning optical system. After being converted into a beam and incident on an optical element 228 of a uniaxial crystal and separated so that two mutually orthogonal linearly polarized beams are shifted in parallel in the sub-scanning direction, they are introduced along the rotation axis of the spinner mirror device 16 Then, the light is reflected and deflected by the reflecting mirror surface 18 </ b> A and guided to the recording medium 14.

  At the same time, in the inner drum exposure apparatus 10, the third laser beam Lc modulated and output in accordance with the image information from the third semiconductor laser light source 230 C controlled by the central controller and the laser driver is collimated. A parallel beam is transmitted through a parallel plate 236 by a mating lens (collimator lens) 232 and then incident on a polarization beam splitter 238. At this time, since the third laser beam Lc is P-polarized with respect to the reflection surface of the polarization beam splitter 238, it travels through the polarization beam splitter 238.

  The fourth laser beam Ld modulated and output according to the image information from the fourth semiconductor laser light source 230D is converted into a parallel beam by the collimating lens (collimator lens) 234, and the half-wave plate 244 is used. , The polarization direction is rotated by 90 ° to become S-polarized light, and then enters the polarization beam splitter 238.

  Then, the fourth laser beam Ld becomes S-polarized light and is reflected by the reflecting surface of the polarization beam splitter 238, and is polarized and coaxially combined with the third laser beam Lc to travel on the optical path. Then, the third laser beam Lc and the fourth laser beam Ld, which are polarization-coaxially combined, are reflected by the reflecting mirror 114 on the optical path and deflected in the X-axis direction by the acoustooptic device 116 which is a light deflecting unit. Then, the light is deflected in the Y-axis direction by an acousto-optic element 118 that is a light deflecting unit.

  Further, the deflected and coaxially combined third laser beam Lc and fourth laser beam Ld are collected by the second condenser lens 120 and then reflected by the reflecting portion 111 of the partial optical function member 104. Then, the light passes through the third condenser lens 106 in the optical system on the light source side and passes through the quarter wavelength plate 107. The third laser beam Lc and the fourth laser beam Ld, which are deflected and coaxially combined, are converted into right circularly polarized light and left circularly polarized light when passing through the quarter-wave plate 107, respectively, on the scanning plane. Then, the light passes through the fourth condenser lens 108 for focusing the light and is guided to the spinner mirror device 16 of the scanning optical system including the quarter-wave plate 226 and the uniaxial crystal optical element 228.

  The third laser beam Lc and the fourth laser beam Ld converted into right circularly polarized light and left circularly polarized light are linearly polarized light orthogonal to each other when passing through the quarter wavelength plate 226 of the scanning optical system. After being converted into a beam and incident on an optical element 228 of a uniaxial crystal and two linearly polarized beams orthogonal to each other are separated so as to be shifted in parallel in the sub-scanning direction, a predetermined interval from the rotation axis of the spinner mirror device 16 It is introduced along the opened straight line, reflected and deflected by the reflecting mirror surface 18A, and guided to the recording medium 14.

  That is, according to the inner drum exposure apparatus 10, the first, second, third, and fourth light emitted from the first, second, third, and fourth semiconductor laser light sources 230A, 230B, 230C, and 230D, respectively. Since the third and fourth laser beams La, Lb, Lc, and Ld are irradiated onto the recording medium 14 and simultaneously exposed, the exposure process can be performed efficiently and quickly.

  Next, a method for rationally performing exposure processing by switching the resolution in the inner drum exposure apparatus 10 having four multi-beam exposure systems will be described.

  The inner drum exposure apparatus 10 having the four multi-beam exposure systems will be described with reference to FIG.

  Here, in the inner drum exposure apparatus 10, the diameters of the beam spots a, b, c, and d are changed in accordance with each resolution in the optical system before being incident on the spinner mirror device 16. At the same time, the inner drum exposure apparatus 10 changes and adjusts the speed of moving the spinner mirror device 16 in the sub-scanning direction in accordance with the resolution so as to match the resolution at that time.

When recording with a resolution of 1200 dpi (1200 dpi to 1270 dpi) in the inner drum exposure apparatus 10 that performs exposure with the four beams, the acoustooptic element 116 and the acoustooptic element 118 are controlled to add a minute deflection to the scanning surface. The amount of shift in the sub-scanning direction is set to 2 pixels (42, 3 μm), and exposure is performed in the 1200 dpi state shown in FIG.
That is, four beam spots a, b, c, and d (first, second, third, and fourth beam spots) by four laser beams La, Lb, Lc, and Ld are arranged in a line at equal intervals. Exposure is performed under the condition.

  When exposure is performed at a resolution of 2400 dpi (2400 dpi to 2540), the acousto-optic element 116 and acousto-optic element 118 are controlled so that a slight deflection is applied and the amount to be shifted in the sub-scanning direction on the scanning plane is 3 Exposure is performed in the state of 2400 dpi shown in the second row from the top of FIG. 4 with a pixel size (31.75 μm).

  That is, when exposure is performed with this resolution set to 2400 dpi, by controlling the acousto-optic element 116 and the acousto-optic element 118, the interval between adjacent beam spots b and c is set to one pixel at 2400 dpi. At the same time, exposure is performed so that the space between the beam spots c and d, which are exposed at the first time, is filled with the beam spot a that is exposed at the second time.

  Further, the exposure is performed so that the unexposed position between the beam spots c and d at the time of the second exposure is filled with the beam spot a to be exposed at the third time. In this way, the entire recording medium 14 is exposed. Of course, each of the beam spots a, b, c, and d is subjected to exposure processing with the laser beams La, Lb, Lc, and Ld that are modulated in accordance with the required image information.

  When exposure is performed at a resolution of 2400 dpi (2400 dpi to 2540), exposure can be performed in a state of another mode at 2400 dpi shown in the third row from the top in FIG.

  When this resolution is exposed in another mode of 2400 dpi, by controlling the acoustooptic element 116 and the acoustooptic element 118, the beam spot c enters between the beam spot a and the beam spot b, and the beam spot b Exposure processing is performed by shifting predetermined beam spots by one pixel so that the beam spot d comes to the side. When exposure processing is performed in this way, each beam spot a, b, c, d is repeatedly exposed, so that the exposure processing is performed at 2400 dpi shown in the second row from the top in FIG. 4 described above. There is no need for interlace recording.

  Further, when exposure is performed with a resolution of 3600 dpi (3600 dpi to 3810 dpi), the acoustooptic element 116 and acoustooptic element 118 are controlled to add 2 to the amount of shift in the sub-scanning direction on the scanning plane by adding a minute deflection. Exposure is performed in the state of 3600 dpi shown in FIG. 4 for the pixel (14.l μm).

  That is, when exposure is performed with this resolution set to 3600 dpi, by controlling the acoustooptic element 116 and the acoustooptic element 118, the interval between adjacent beam spots b and c is set to one pixel at 3600 dpi. At the same time, exposure is performed so that the space between the beam spots c and d, which are exposed at the first time, is filled with the beam spot a that is exposed at the second time.

  Further, the exposure is performed so that the unexposed position between the beam spots c and d at the time of the second exposure is filled with the beam spot a to be exposed at the third time. In this way, the entire recording medium 14 is exposed. Of course, each of the beam spots a, b, c, and d is subjected to exposure processing with the laser beams La, Lb, Lc, and Ld that are modulated in accordance with the required image information.

  Next, in the inner drum exposure apparatus 10 according to the first embodiment and the second embodiment, another configuration example for performing exposure processing by performing beam division and performing main scanning on the recording surface of the recording medium 14. Will be described with reference to FIG. FIG. 9 shows a configuration corresponding to the inner drum exposure apparatus 10 according to the second embodiment. The inner drum exposure apparatus 10 according to the first embodiment has the same configuration as the two laser beams La and Lb shown in FIG.

  As shown in FIG. 9, in the inner drum exposure apparatus 10, the holder 24 fixed to the rotary shaft member 18 of the spinner mirror device 16 is connected to the quarter-wave plate 226 and the uniaxial crystal optical element 228. Then, a half-wave plate 246 that is a polarization control element and a uniaxial crystal optical element 248 as a light beam splitting element are installed. Although not shown, the quarter-wave plate 226, the uniaxial crystal optical element 228, the half-wave plate 246, and the uniaxial crystal optical element 248 are configured to rotate integrally with the reflecting mirror surface 18A. To do.

  In the inner drum exposure apparatus 10 configured as described above, for example, the first laser beam La and the second laser beam Lb that are coaxially multiplexed from the optical system on the light source side and converted into right circularly polarized light and left circularly polarized light, respectively. And the pair of the third laser beam Lc and the fourth laser beam Ld converted into the right circularly polarized light and the left circularly polarized light pass through the quarter wavelength plate 226 of the scanning optical system, respectively. A set of a first laser beam La and a second laser beam Lb in the sub-scanning direction when passing through a uniaxial crystal optical element 228 and being converted into linearly polarized light beams orthogonal to each other; 3 is divided into a set of the third laser beam Lc and the fourth laser beam Ld.

  Furthermore, the set of the first laser beam La and the second laser beam Lb and the set of the third laser beam Lc and the fourth laser beam Ld divided in the sub-scanning direction are polarization control elements. When passing through the half-wave plate 246, the polarization direction of the light beam is rotated by 45 °, and when passing through the second uniaxial crystal optical element 248 as a splitting element, the first laser beam La And the third laser beam Lc are divided in the sub-scanning direction with substantially equal light amount, and the second laser beam Lb and the fourth laser beam Ld are divided in the sub-scanning direction with substantially equal light amount.

  In this inner drum exposure apparatus, although not shown, the first quarter wave plate and the first uniaxial crystal optical element arranged on the optical path are divided in the sub-scanning direction. The laser beam and the second laser beam are each circularly polarized by a second quarter-wave plate that is a polarization control element disposed downstream of the optical element of the first uniaxial crystal, and further the optical path. The light beams that are each circularly polarized by the optical element of the second uniaxial crystal as the splitting element disposed on the downstream side may be split in equal amounts in the sub-scanning direction.

  In the inner drum exposure apparatus 10 configured in this way, the condensing spot diameter of the light beam before being divided with the same amount of light in the sub-scanning direction of each laser beam is made smaller than each recording pixel, and the first as a dividing element. By setting the division width of the uniaxial crystal optical element 248 to about half a pixel, the rectangular shape can be made closer to the sub-scanning direction, and the optical element 248 can be sharpened by being narrowed in the main scanning direction. It is possible to obtain a spot shape in a simple state (the edge portion of the beam spot becomes a steep state). Thereby, it is possible to improve the quality of the recording pixel.

It is a schematic block diagram which shows the principal part of the inner drum exposure apparatus concerning 1st Embodiment of this invention. It is explanatory drawing which shows the outline of a structure of the optical path from the light source used for the inner drum exposure apparatus concerning 2nd Embodiment of this invention to a spinner mirror apparatus. It is an expansion perspective view which takes out and shows the partial optical function member arrange | positioned on the optical path from the light source used for the inner drum exposure apparatus concerning 2nd Embodiment of this invention to a spinner mirror apparatus. It is explanatory drawing which shows the method for switching the resolution and performing a rational exposure process with the inner drum exposure apparatus concerning 2nd Embodiment of this invention. It is explanatory drawing which shows the structure of the separation element of a light beam and splitting element with which the spinner mirror apparatus used for the inner drum exposure apparatus concerning 2nd Embodiment of this invention is mounted | worn. It is explanatory drawing which shows the characteristic of the optical element of the uniaxial crystal which radiate | emits and separates the light beam which can be used for the inner drum exposure apparatus concerning 1st or 2nd embodiment of this invention in a different angle direction. A surface S ′ perpendicular to the rotation axis of the spinner mirror device of the laser beam deflected by the light deflecting means for deflecting in the X axis direction and the Y axis direction used in the inner drum exposure apparatus according to the second embodiment of the present invention. It is explanatory drawing which shows the locus | trajectory above. It is explanatory drawing which shows the structure of the control circuit for the optical deflection | deviation means which deflects to the X-axis direction and Y-axis direction used for the inner drum exposure apparatus concerning 2nd Embodiment of this invention. It is explanatory drawing which shows the structure of the separation element of a light beam and splitting element with which the spinner mirror apparatus used for the inner drum exposure apparatus concerning 2nd Embodiment of this invention is mounted | worn.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inner drum exposure apparatus 12 Support body 14 Recording medium 16 Spinner mirror apparatus 18 Rotating shaft member 18A Reflective mirror surface 28 Optical element 38 of uniaxial crystal Polarizing beam splitter 52 1/4 wavelength plate 104 Partial optical function member 1071/4 wavelength plate 116 acousto-optic element 118 acousto-optic element 2261/4 wave plate 228 uniaxial crystal optical element 238 polarization beam splitter 2461/2 wave plate 248 uniaxial crystal optical element 250 crystal plate

Claims (3)

The first P-polarized light beam emitted from the first light source and the second S-polarized light beam emitted from the second light source are polarization-coaxially combined to travel on the same optical path. A first and second set of polarization coaxial light beams combined;
The light beam converted to the third P-polarized light emitted from the third light source and the light beam converted to the fourth S-polarized light emitted from the fourth light source are polarized and coaxially combined, and A third and a fourth set of polarization coaxial combined light beams traveling on the optical path of
The first and second sets of polarization coaxial combined light beams and the third and fourth sets of polarization coaxial combined light beams are converted into light beams that travel substantially in parallel on the optical path. A light beam is emitted to a spinner mirror device through an imaging optical system for forming an image on the recording medium,
On the optical path before entering the spinner mirror device, the first and second sets, and the third and fourth sets of polarization-coaxially combined light beams are rotated clockwise and circularly polarized light respectively. The circularly polarized light is converted into a circularly polarized light, and the right circularly polarized light beam and the left circularly polarized light beam are mounted so as to rotate integrally with the uniaxial crystal and the reflecting mirror surface installed in the spinner mirror device. When the exposure is performed at a predetermined resolution on the recording medium after being converted into linearly polarized light orthogonal to each other by the quarter wavelength plate and reflected by the reflecting mirror surface by the uniaxial crystal placed thereafter. The orthogonally polarized light beams orthogonal to each other are shifted by one pixel in the sub-scanning direction,
The direction in which light travels in at least one of the first and second sets of polarization coaxial combined light beams and the third and fourth sets of polarization coaxial combined light beams. The first image formed on the recording medium is formed by applying a minute deflection by at least one of the light deflecting means for deflecting in the X-axis direction orthogonal to the light deflecting means and the light deflecting means for deflecting in the Y-axis direction orthogonal to these. The four beams are equally spaced so as to be shifted by two pixels on the recording medium into a set of the beam spot and the second beam spot, and a set of the third beam spot and the fourth beam spot. A method of switching resolution in an inner drum type multi-beam exposure system of an inner drum exposure apparatus that forms an image in a lined state and performs scanning exposure,
When exposure processing is performed while switching to a resolution that is approximately twice the predetermined resolution, the diameter of the beam spot is made to correspond to the resolution that is switched to approximately twice in the imaging optical system before entering the spinner mirror device. , And
The movement of the spinner mirror device in the sub-scanning direction is controlled by the sub-scanning moving means so as to correspond to the resolution switched approximately twice,
By applying a minute deflection by the light deflection means, a set of the first beam spot and the second beam spot imaged on the recording medium, the third beam spot, and the fourth beam. The spot set and the recording medium are shifted by an amount corresponding to one pixel after approximately double resolution conversion on the recording medium,
An exposure process for shifting so that the third beam spot enters between the first beam spot and the second beam spot, and the fourth beam spot comes next to the second beam spot. By performing the above operation, scanning exposure is performed on the recording medium, and a resolution switching method in an inner drum type multi-beam exposure system. The first P-polarized light beam emitted from the first light source and the second S-polarized light beam emitted from the second light source are polarization-coaxially combined to travel on the same optical path. A first and second set of polarization coaxial light beams combined;
The light beam converted to the third P-polarized light emitted from the third light source and the light beam converted to the fourth S-polarized light emitted from the fourth light source are polarized and coaxially combined, and A third and a fourth set of polarization coaxial combined light beams traveling on the optical path of
The first and second sets of polarization coaxial combined light beams and the third and fourth sets of polarization coaxial combined light beams are converted into light beams that travel substantially in parallel on the optical path. A light beam is emitted to a spinner mirror device through an imaging optical system for forming an image on the recording medium,
On the optical path before entering the spinner mirror device, the first and second sets, and the third and fourth sets of polarization-coaxially combined light beams are rotated clockwise and circularly polarized light respectively. The circularly polarized light is converted into a circularly polarized light, and the right circularly polarized light beam and the left circularly polarized light beam are mounted so as to rotate integrally with the uniaxial crystal and the reflecting mirror surface installed in the spinner mirror device. When the exposure is performed at a predetermined resolution on the recording medium after being converted into linearly polarized light orthogonal to each other by the quarter wavelength plate and reflected by the reflecting mirror surface by the uniaxial crystal placed thereafter. The orthogonally polarized light beams orthogonal to each other are shifted by one pixel in the sub-scanning direction,
The direction in which light travels in at least one of the first and second sets of polarization coaxial combined light beams and the third and fourth sets of polarization coaxial combined light beams. By applying a minute deflection by at least one of a light deflecting means that deflects in the X-axis direction orthogonal to the Y-axis direction and a light deflecting means that deflects in the Y-axis direction orthogonal to these, the first image formed on the recording medium is formed. One beam spot and the second beam spot group, the third beam spot and the fourth beam spot group are shifted by two pixels on the recording medium so that four beams are generated. A method of switching resolution in an inner drum type multi-beam exposure system of an inner drum exposure apparatus in which images are formed in a state of being arranged at equal intervals to perform scanning exposure,
When exposure processing is performed by switching to a resolution approximately twice the predetermined resolution, the diameter of the beam spot is made to correspond to the resolution switched to approximately twice in the imaging optical system before entering the spinner mirror device. Scaling,
The movement of the spinner mirror device in the sub-scanning direction is controlled by the sub-scanning moving means so as to correspond to the resolution switched approximately twice,
By applying a minute deflection by the light deflecting means, a set of the first beam spot and the second beam spot formed on the recording medium, the third beam spot, and the fourth beam. The spot set and the recording medium are shifted by an amount corresponding to one pixel after approximately double resolution conversion on the recording medium,
When performing the first exposure, an unexposed portion of one pixel having a resolution of approximately twice is left between the first beam spot and the second beam spot, and the third beam spot and the second beam spot The exposure is performed so as to leave an unexposed portion corresponding to one pixel having a resolution of approximately double between the fourth beam spot and the third beam spot is exposed at a position adjacent to the second beam spot. And
The unexposed position between the third beam spot and the fourth beam spot exposed in the first time is filled with the first beam spot exposed in the second time, and the exposed in the first time. Repeating the exposure process so that the unexposed position between the fourth beam spot and the third beam spot exposed at the second time is filled with the second beam spot exposed at the second time. The method of switching the resolution in the inner drum type multi-beam exposure system, characterized in that scanning exposure is performed on the recording medium. When the inner drum exposure apparatus having the four multi-beam exposure systems is switched to a resolution that is approximately three times the predetermined resolution and is subjected to exposure processing, the light deflecting means applies a small deflection to the spinner mirror apparatus. In addition, the recording medium includes the first beam spot and the second beam spot that are imaged on the recording medium, the third beam spot, and the fourth beam spot group. The amount corresponding to 2 pixels after the resolution conversion of about 3 times is shifted to each other,
In the first exposure, the third beam spot is exposed at a position adjacent to the second beam spot between the first beam spot and the second beam spot,
An operation of performing an exposure process so that an unexposed position between the second beam spot exposed at the first time and the fourth beam spot is filled with the first beam spot exposed at the second time. 3. The method of switching resolution in the inner drum multi-beam exposure system according to claim 1, wherein scanning exposure is performed on the recording medium by repeating the above.

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