JP2009015223A - Inner drum exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inner drum exposure apparatus that scans and exposes a recording medium with two light beams split by using polarized light, in which a cubic prism mirror is used as a light polarizing means and focal positions in the optical axis direction of the two light beams can be aligned even when a photo-elastic effect occurs in the prism mirror by high-speed rotation. <P>SOLUTION: At least one of the two light beams incident to a multiplexing means that multiplexes the light beams is prepared to be a converging or diverging light beam according to the misalignment of condensation positions of the light beams caused by distortion of the prism mirror. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inner drum-type exposure apparatus that performs scanning exposure by holding a scanned body such as a recording medium on a cylindrical inner peripheral surface. Specifically, the present invention combines two light beams, and again 2 The present invention relates to an inner drum exposure apparatus capable of properly condensing two light beams at a predetermined position in the optical axis direction in an inner drum exposure apparatus that scans by dividing into books.

The recording medium is two-dimensionally supported by a light beam that is main-scanned in the circumferential direction of the arc by a spinner (optical deflector) that supports the recording medium on an arc-shaped inner circumferential surface and rotates a reflecting surface around the center line of the arc. An inner drum exposure apparatus (cylindrical inner surface scanning exposure apparatus) that performs scanning exposure is known.
In such an inner drum exposure apparatus, a light beam separating means such as a Wollaston prism or a beam displacer is used, for example, the light beams modulated independently of each other are combined to rotate the light polarization means. There is also known an apparatus that enters a spinner, deflects / scans in the circumferential direction of the inner drum, separates the combined light beams into multi-beams, and simultaneously scans with a plurality of light beams.

As an example, Patent Document 1 discloses an inner drum exposure apparatus having a schematic configuration shown in FIG.
The inner drum exposure apparatus 200 combines the light beams emitted from the light source units 202a and 202b having the light source and the collimator lens, and separates them again to form two light beams having an arc-shaped inner peripheral surface. The recording medium P held on the inner surface of the cylindrical support 204 is two-dimensionally scanned and exposed with two light beams.

In the illustrated inner drum exposure apparatus 200 (hereinafter referred to as exposure apparatus 200), the light sources 202a and 202b of the light beam are modulated and driven independently of each other. The light beams La and Lb emitted from the light sources 202a and 202b are converted into parallel light (parallel beam) by a collimator lens (not shown), and the light path is adjusted by a parallel plate or a prism (both not shown) and then polarized. The beams are combined by the beam splitter 208, and an apparent optical beam having the same optical axis is obtained.
Here, the light beams La and Lb emitted from the light sources 202a and 202b are both p-polarized light beams with respect to the polarization beam splitter 208, but the light beam Lb emitted from the light source 202b is ½ in the middle. The polarization direction (polarization plane) is rotated by 90 ° by the wave plate 210 to obtain an s-polarized light beam. That is, the light beams La and Lb combined by the polarization beam splitter 208 are light beams whose polarization directions are orthogonal to each other.

The linearly polarized light beams La and Lb combined by the polarization beam splitter 208 travel along the center line of the cylinder of the support 204 and enter the quarter wavelength plate 212.
This quarter-wave plate 212 is arranged in a state where the crystal optical axis is inclined by 45 ° with respect to the polarization direction of the light beam. Further, the polarization directions of the light beams La and Lb are orthogonal to each other. Therefore, the light beams La and Lb that have passed through the quarter-wave plate 226 are circularly polarized light beams whose rotation directions are opposite to each other, one rotation to the left and the other to the right rotation.

The light beams La and Lb that have been circularly polarized by the quarter-wave plate 212 are then condensed by the condenser lens 214 so as to have a predetermined beam diameter on the inner surface of the support 204 (the surface of the recording medium P). And enters the spinner 216.
The spinner 216 includes a second quarter wave plate 220, a beam displacer 222, a spinner mirror 224, a motor 226, and a holder 228. The spinner mirror 224 is fixed in a cylindrical holder 228, and the quarter wavelength plate 220 and the beam displacer 222 are fixed near the upper surface of the holder 228 (upstream end surface of the light beam optical path). The four-wave plate 220, the beam displacer 222, and the spinner mirror 224 are integrally rotated by a motor 226. Further, the holder 228 is formed with an opening through which the light beam passes in the direction in which the light beam is reflected by the spinner mirror 224.

The light beams La and Lb incident on the spinner 216 are first returned from the circularly polarized light whose rotation direction is reverse to the linearly polarized light beam whose polarization direction is orthogonal by the ¼ wavelength plate 220, and is returned to the beam displacer 222. Incident.
The beam displacer 222 is an optical element made of a uniaxial crystal, and the crystal optical axis of the uniaxial crystal is disposed with an inclination of 45 ° with respect to the normal line of the crystal incident surface of the light beam. Such a uniaxial crystal shifts the component of the extraordinary ray of the light beam in parallel, and divides it into two light beams of an ordinary ray and an extraordinary ray. Further, the beam displacer 222 is arranged so that the division direction is a sub-scanning direction (a center line direction of the support 204) described later.
Therefore, the linearly polarized light beams La and Lb that are incident on the beam displacer 222 have two components having parallel optical paths (optical axes) in which components corresponding to extraordinary rays are shifted in parallel in the sub-scanning direction. It becomes a light beam.

The light beams La and Lb divided by the beam displacer 222 are incident on the spinner mirror 224.
The spinner mirror 224 is provided with a reflection surface at an angle of 45 ° with respect to the optical axes of the combined light beams La and Lb (that is, the center line of the inner surface of the cylindrical support 204). It is rotated by a motor 226 at the center. Therefore, the two divided light beams are deflected and scanned in the circumferential direction (main scanning direction) of the cylindrical inner peripheral surface of the support 204.

  In the exposure apparatus 200, the spinner 216 and the condenser lens 214 are integrated in a sub-scanning direction that coincides with the optical axis direction of the light beams La and Lb (the direction of the center line of the inner surface of the support 204) by scanning means (not shown). (Sub-scan). Accordingly, the recording medium P held on the inner surface of the support 204 is two-dimensionally scanned and exposed by the two light beams La and Lb that are main-scanned in the circumferential direction.

JP 2006-91377 A

  In an apparatus such as the exposure apparatus 200 that scans and exposes the recording medium P with two light beams modulated independently of each other, in order to perform proper image recording, the two light beams in the optical axis direction are used. It is necessary to match the focus position.

Here, in such an exposure apparatus 200, the light deflecting means such as the spinner mirror 224 rotates at a very high speed of, for example, about 40,000 rpm.
As described above, the spinner 216 needs to fix the second quarter-wave plate 220 and the beam displacer 222 that rotate integrally with the upper part of the spinner mirror 224. However, the spinner mirror 224 has a problem in that it is difficult to balance at high speed rotation, and the mirror surface tends to be mechanically distorted.
In contrast, spinner mirrors using cubic prism mirrors have already been commercialized. With this prism mirror, the quarter wavelength plate and the beam displacer can be fixed relatively easily on the upper part.
However, in this case, as conceptually shown in FIG. 8, when this cubic prism mirror is used, the prism mirror 230 is distorted during high-speed rotation, and the s-polarized light and p-polarized light are different from each other due to the photoelastic effect. It has been found that there is a problem that the positions of the condensing points of the two light beams La and Lb are shifted in the optical axis direction.

  Therefore, the two light beams La and Lb having linearly polarized light orthogonal to each other may be out of focus in the direction of the optical axis when entering the recording medium P, and proper exposure may not be performed.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. A recording medium is held on a cylindrical inner surface support, and two light beams modulated independently are combined and divided. In an inner drum exposure apparatus that scans and exposes a recording medium in the circumferential direction of a cylinder with two light beams, a cubic prism mirror that can fix a quarter-wave plate and a beam displacer relatively easily is used as a light polarization unit. And an inner drum exposure apparatus that can properly adjust the focus position of the two light beams in the optical axis direction on the surface of the recording medium even if the prism mirror is distorted due to high-speed rotation. is there.

  In order to achieve the above object, an inner drum exposure apparatus of the present invention includes a first light source unit that emits a linearly polarized light beam, and linearly polarized light in a direction orthogonal to the light beam emitted by the first light source unit. A second light source unit that emits a light beam, a multiplexing unit that combines the light beams emitted from the first light source unit and the second light source unit, and a light beam that is combined by the multiplexing unit rotate with each other. A first polarizing member for converting into two circularly polarized light beams having opposite directions, a support having an arc-shaped inner peripheral surface and holding a recording medium on the inner peripheral surface, and supporting the light beam A deflecting surface that reflects toward the inner peripheral surface of the body, and rotating the deflecting surface about the center line of the inner peripheral surface of the support, thereby allowing the light beam to be reflected on the inner peripheral surface of the support. It has a cubic prism mirror that scans in the main scanning direction that matches the circumferential direction The light deflection means, the condensing optical system for condensing the circularly polarized light beam at a predetermined position, and the light deflection means by a predetermined path traveling along the central axis of the inner peripheral surface of the support. An optical path adjusting means that is incident on the optical path, and two circularly polarized light beams that are arranged on the optical path of the light beam adjusted by the optical path adjusting means and rotated integrally with the light polarizing means. A second polarizing member for returning to a linearly polarized light beam, and a light beam converted into linearly polarized light by the second polarizing member into two light beams traveling in parallel are rotated together with the light polarizing means. The combined beam separating means, the condensing optical system, the light deflecting means, the second polarizing member, and the combined beam separating means are integrally moved in the direction of the central axis of the inner peripheral surface of the support. Means, and the first light source unit and An inner drum exposure apparatus characterized in that at least one of the second light source units emits a converged or diverging light beam so as to correct a converging position deviation of the light beam due to rotation of the cubic prism mirror. provide.

In such an inner drum exposure apparatus according to the present invention, at least one of the first light source unit and the second light source unit emits a light beam that converges or diverges so as to correct the converging position deviation. Preferably, at least one of the first light source unit and the second light source unit has a relay lens that converges or diverges parallel light, so that a light beam that converges or diverges so as to correct the converging position deviation. Is preferably emitted.
Further, it is preferable that the second polarizing means and the combined beam separating means are fixed to the prism mirror.

According to the present invention having the above configuration, the recording medium (scanned medium) is held on the inner surface of the support having the cylindrical inner surface, and the two light beams modulated independently are combined and divided. In an inner drum exposure apparatus that scans and exposes a recording medium in the circumferential direction of a support with two light beams, a cubic prism mirror that can fix a quarter-wave plate and a beam displacer relatively easily is optically polarized. Further, at least one of the two light beams before being combined is extremely slightly used so as to correct the deviation of the converging position of the light beam caused by the distortion of the cubic prism mirror caused by the high-speed rotation. In addition, a light beam that diverges or converges is used.
Therefore, according to the inner drum exposure apparatus of the present invention, even if the light deflecting means is distorted by high-speed rotation and the light beam condensing position shifts in the optical axis direction, the light beam corrects this light converging position shift. Therefore, it is possible to make the shape and beam diameter of the two light beams on the surface of the recording medium appropriate by matching the condensing positions in the optical axis direction of the two light beams. That is, appropriate image exposure with two appropriate light beams can be stably performed.

  Hereinafter, the inner drum exposure apparatus of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

FIG. 1 shows a conceptual diagram of an example of an inner drum exposure apparatus of the present invention.
An inner drum exposure apparatus 10 (hereinafter referred to as exposure apparatus 10) shown in FIG. 1 holds a recording medium P (scanned medium) on the inner surface of a support 12 having a cylindrical inner surface, and the center of the cylinder. An inner drum exposure apparatus (cylindrical inner surface scanning exposure apparatus) that deflects a light beam using a cubic prism mirror rotating around a line as a light deflecting means and scans the light beam in the circumferential direction of the inner surface of the cylinder. Thus, the recording medium P is simultaneously scanned and exposed by the two light beams L modulated independently of each other.
The exposure apparatus 10 in the illustrated example basically includes a support 12 indicated by an imaginary line (one-dot chain line) in the drawing, a first light source unit 14a that emits a light beam La, and a second light source unit 14b that emits a light beam Lb. , A polarizing beam splitter 16, a beam alignment optical system 18, a ¼ wavelength plate 20, a condenser lens 22, a spinner 24, and a control means 26.

The control unit 26 includes a CPU and the like, and controls driving and operation of the entire exposure apparatus 10.
The control unit 26 drives the light sources 31 of the first light source unit 12a and the second light source unit 12b according to the image to be recorded on the recording medium P.

The support (drum) 12 has a cylindrical inner peripheral surface (cylindrical inner surface), and holds the recording medium P in close contact with the inner peripheral surface.
The recording medium P is held (fixed) on the support 12 by using an inner drum type (cylindrical inner surface scanning) such as a method using suction, a method using static electricity, a method using a fixing member using a magnet or fitting. A known method used in a type exposure apparatus may be used. Further, the supply and discharge of the recording medium P to and from the support 12 may be performed manually or automatically using a known method used in an inner drum type exposure apparatus.

  The first light source unit 14a emits a linearly polarized light beam La modulated in accordance with an image to be recorded and enters a predetermined position of the polarization beam splitter 16, and is basically parallel to the light source unit 30a. And a flat plate 33.

The light source unit 30a includes a light source 31 and a collimator lens 32 as conceptually shown in FIG. The light source 31 is a known light beam light source that emits a linearly polarized light beam (laser beam) such as an LD. The collimator lens 32 is a known collimator lens that changes the light beam La emitted from the light source 31 into parallel light (parallel beam) (collimates the light beam La). In the illustrated example, the light source 31 emits a p-polarized linearly polarized light beam La to the polarizing beam splitter 16 (its reflection surface).
The parallel flat plate 33 is a transparent optical glass flat plate, and in order to combine the light beams La and Lb by the polarization beam splitter 16 with high accuracy, the optical path of the light beam La emitted from the light source unit 30a is shifted in parallel (optical path). Is shifted in a plane direction perpendicular to the optical axis).

  Similarly to the first light source unit 14a, the second light source unit 14b emits a linearly polarized light beam Lb modulated in accordance with the image to be recorded, and enters the polarization beam splitter 16 at a predetermined position. Basically, the light source unit 30b includes two prisms, ie, a first prism 34 and a second prism 36, and a half-wave plate 38.

The light source unit 30b has the same configuration as that of the light source unit 30a. The light source unit 30b includes a light source 31 for a light beam Lb and a collimator lens 32, and is a p-polarized linearly polarized light beam La with respect to the polarization beam splitter 16. Is emitted.
The first prism 34 and the second prism 36 are configured to accurately combine the light beams La and Lb by the polarization beam splitter 16 with an angle of the light beam Lb emitted from the light source unit 30b emitted from the light source unit 30a ( For adjusting the direction of travel).

  In the exposure apparatus 10 of the present invention, when the polarization beamsplitter 16 can combine the light beams La and Lb with high accuracy according to the positional accuracy of the light source unit, the parallel flat plate 33, and The first prism 34 and the second prism 36 are not required, or may have only one of a parallel plate and a prism.

  The half-wave plate 38 rotates the polarization direction (polarization plane) of the linearly polarized light beam Lb emitted from the light source unit 30b by 90 ° to obtain an s-polarized linearly polarized light beam. As described above, since the first light source unit 14a emits the p-polarized light beam La, the light beams La and Lb incident on the polarization beam splitter 16 are polarized with respect to the p-polarized light and the s-polarized light. Becomes a linearly polarized light beam.

Here, in the exposure apparatus 10 of the present invention, at least one of the light source unit 30a and the light source unit 30b corresponds to the positional deviation of the condensing points of the light beams La and Lb caused by the high-speed rotation of the prism mirror 64 of the spinner 24. Thus, the distance between the light source 31 and the collimator 36 is adjusted, and a light beam that converges or diverges (the beam diameter of the light beam is reduced or expanded) is emitted. A light source unit that does not emit a convergent or divergent light beam emits parallel light (parallel beam) as in a normal light beam exposure apparatus.
This will be described in detail later.

The polarization beam splitter 16 is a known polarization beam splitter that separates a light beam line into two by a birefringent crystal.
In the illustrated exposure apparatus 10, the light source units 30 a and 30 b are arranged at the same position on the reflecting surface of the polarization beam splitter 16 so that the light beams La and Lb are incident on the optical paths orthogonal to each other.
The polarization beam splitter 16 transmits the light beam La from the first light source unit 14a through the reflection surface, and reflects the light beam Lb from the second light source unit 14b at the reflection surface, thereby having polarization directions orthogonal to each other. The two linearly polarized light beams La and Lb are combined into an apparently single light beam having the same optical axis. In the following description, particularly when there is no need to distinguish between the light beam La and the light beam Lb, they are collectively referred to as a light beam L.

Further, in the illustrated exposure apparatus 10, the first light source unit 14 a, the second light source unit 14 b, and the polarization beam splitter 16 are configured such that the optical axis of the light beam L combined by the polarization beam splitter 16 is Arranged to coincide with the center line of the cylinder.
That is, these members constitute the optical path adjusting means in the present invention.

The beam alignment optical system 18 multiplexes the light beams La and Lb with the polarization beam splitter 16 with high accuracy, and the parallel plate 33 of the first light source unit 14a and the first prism 34 of the second light source unit 14b. In addition, the angle of the second prism 36 is adjusted.
In the illustrated example, the beam alignment optical system 18 includes a beam splitter 50, a lens 52, and a beam position detector 54 (hereinafter referred to as PSD 54).

The beam splitter 50 is a known beam splitter that reflects (deflects) a part of the light beam L in a predetermined direction toward the PSD 54, and the lens 52 reflects the light beam L reflected by the beam splitter 50 on the PSD 54. Focus on the light receiving surface. The beam splitter 50 is moved to a reflection position shown in FIG. 1 that acts on the optical path of the light beam L and a retreat position that is completely retracted from the optical path of the light beam L by a moving unit (not shown). The moving means may be a known plate-like moving means such as a mirror.
The PSD 54 is a photoelectric conversion element in which light receiving elements are two-dimensionally arranged, such as a CCD sensor, and detects the position of the light beam reflected by the beam splitter 50.

As will be described in detail later, in the exposure apparatus 10, two linearly polarized light beams La and Lb whose polarization directions are orthogonal to each other are combined to form a circularly polarized light beam, and then returned to the linearly polarized light beam again. After that, it is split into two light beams La and Lb using polarized light, and deflected and scanned in the circumferential direction of the support by the spinner 24. Therefore, in order to perform appropriate exposure in the exposure apparatus 10, it is necessary to combine the light beams La and Lb with high precision by the polarization beam splitter 16 so that the optical axes coincide with each other.
The beam alignment optical system 18 is for adjusting the optical paths (position and direction) of the light beams La and Lb in order to multiplex the light beams La and Lb with high accuracy by the polarization beam splitter 16.

Here, if the light beams La and Lb are combined with high accuracy, the two light beams La and Lb are incident on the same position on the light receiving surface of the PSD 54.
On the other hand, when the incident positions and angles of the light beams La and Lb on the PSD 54 are different, the polarization beamsplitter 16 does not properly combine the light beams La and Lb. Therefore, at this time, the first beam so that the incident angles of the light beams La and Lb to the PSD 54 are matched, that is, the light beams La and Lb can be combined with the polarization beam splitter 16 with high accuracy. The angles of the prism 34 and the second prism 36 are adjusted. Further, since the optical axes of the light beams La and Lb are shifted on the polarization beam splitter 16 by this angle adjustment, the angle of the parallel plate 33 is adjusted in order to correct this shift.

The quarter-wave plate 20 is disposed in the optical path of the light beam L with the crystal optical axis inclined by 45 ° with respect to the linear polarization direction of the light beam L.
Therefore, the light beam L incident / passed to the quarter wavelength plate 20 is converted from linearly polarized light to circularly polarized light beam. Here, since the combined light beams La and Lb are linearly polarized light beams whose polarization directions are orthogonal to each other, the light beams La and Lb are circles having different rotation directions of right rotation and left rotation. It becomes a polarized light beam.

The condensing lens 22 is a lens that condenses the light beam L and causes the inner surface (the surface of the recording medium P) of the support 12 to be incident (imaged) with a predetermined beam spot diameter. The center line, that is, the optical axis of the light beam L is arranged to coincide.
In the exposure apparatus 10, the beam diameter of the light beam L is increased as necessary, downstream of the polarizing beam splitter 16, preferably between the quarter-wave plate 20 and the condenser lens 22. May have a beam expander.

The light beam L that has passed through the condenser lens 22 travels along the center line of the support 12 and then enters the spinner 24.
The spinner 24 deflects and scans the light beam L in the circumferential direction (main scanning direction) of the support. Basically, the quarter wavelength plate 60, the beam displacer 62, and the prism mirror, which are second polarizing members. 64 and a motor 66.

The light beam L incident on the spinner 24 is first converted from a circularly polarized light beam L to a linearly deflected light beam L by the quarter-wave plate 60.
Here, since the light beams La and Lb are circularly polarized light having different rotation directions, the light beams La and Lb that have passed through the quarter-wave plate 60 have the same deflection direction as before the circularly polarized light. The light beam is an orthogonal linearly polarized light beam.

The beam displacer 62 is an optical element made of a uniaxial crystal (optical crystal) that separates a light beam into an ordinary ray Po and an extraordinary ray Pe. As shown conceptually in FIG. Are arranged such that the crystal optical axis of the uniaxial crystal is 45 ° with respect to the incident surface and the normal line.
Such a beam displacer 62 parallelly shifts one of the light beam La and the light beam Lb (the one corresponding to the extraordinary light beam Pe) converted into the linearly polarized light directions orthogonal to each other into two light beams. To separate.

The beam displacer 62 (uniaxial crystal) has a crystal optical axis in a plane formed by the optical axis of the light beam L incident on the prism mirror 64 and the optical axis of the light beam L reflected by the prism mirror 64. Are arranged to exist.
As a result, the light beam L can be made into two light beams obtained by separating the ordinary ray Po and the extraordinary ray Pe in the sub-scanning direction to be described later.

As a beam displacer 62, a crystal is illustrated as a suitable example.
For example, when the interval of one pixel in the exposure apparatus 10 is 10.58 μm, a crystal plate having a thickness of 1.74 mm is used as the beam displacer 62, so that the light beam La or the light beam Lb for one pixel is used. Can be shifted in parallel.
Further, in order to set the accuracy of the separation interval to an error of 0.1 μm or less, the error of the thickness of the crystal plate may be set to ± 18 μm or less. If it is this level, the quartz plate can be processed at a low cost with sufficient accuracy, and also has the advantage of being stable and low in cost as a material. Furthermore, since the relationship of the division width with respect to the inclination angle of the crystal is loose, the beam displacer 62 having a required function can be configured according to the characteristics of the crystal.

The uniaxial crystal constituting the beam displacer 62 is not limited to quartz, and may be configured using uniaxial crystals such as calcite and 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 prism mirror 64 can be suppressed. When calcite is used, it is desirable to use the quarter-wave plate 60 and the beam displacer 62 by bonding them at an angle.

The light beams La and Lb divided by the beam displacer 62 are then incident on a prism mirror (ball prism) 64 and deflected / scanned.
The prism mirror 64 is light deflecting means that reflects a light beam using two prisms, and the motor 66 is a rotational drive source that rotates the prism mirror 64. The prism mirror 64 is rotated at a high speed (for example, 40000 rpm) with the reflection surface set at an angle of 45 ° with respect to the center line of the support 12 (ie, the optical axis of the light beam L) and the motor 66 as the rotation center. Degree).
Therefore, the light beams La and Lb incident on the prism mirror 36 are reflected by the prism mirror 36 to the inner peripheral surface of the support 12 and scanned in the circumferential direction (main scanning direction) of the inner peripheral surface (main scanned). )

Here, as shown in FIG. 1, the beam displacer 62 is fixed (adhered) to the light beam incident surface of the prism mirror 36, and the quarter wavelength plate 60 is fixed (adhered) to the beam displacer 62. ) Therefore, the three members rotate integrally and their positional relationship does not change, that is, the optical positional relationship is always constant.
Therefore, in the spinner 24, the two light beams La and Lb can always be divided in the sub-scanning direction at a predetermined interval regardless of the scanning position by the prism mirror 36 (the rotation angle of the prism mirror 36).

Although not shown, the spinner 24 and the condensing lens 22 are integrated with the exposure apparatus 10, and the direction of the center line of the support 12 (its cylindrical inner surface), that is, the optical axis direction of the light beam L is shown. Sub-scanning means moving in the (sub-scanning direction) is arranged.
As described above, the light beam is main-scanned in the circumferential direction of the inner peripheral surface of the support 12 by the prism mirror 36. Therefore, the entire surface of the recording medium P held on the inner peripheral surface of the support 12 can be scanned and exposed two-dimensionally by sub-scanning in the center line direction of the spinner 24 and the like.
The sub-scanning means is not particularly limited, and various known linear movement methods such as a screw transmission method can be used.

Here, in the spinner 24, in order to deflect and scan the light beam L, the prism mirror 64 (light deflecting means) is rotated at a high speed of, for example, 40,000 rpm as described above.
As described above, in the inner drum exposure apparatus that performs the multi-beam scanning exposure using the polarization direction of the linearly polarized light beam, the cubic prism mirror 64 is used as the light polarization means, so that a quarter wavelength is obtained. The plate 60 and the beam displacer 62 can be fixed relatively easily. On the other hand, in particular, as in the illustrated example, when a cubic prism mirror 64 is used as the light deflection means, the prism mirror 64 is distorted during high-speed rotation, and s-polarized light is applied to the prism mirror 64 by the photoelastic effect. The positions of the condensing points of the two light beams La and Lb having different p-polarizations are shifted in the optical axis direction.
As a result, the two light beams La and Lb incident on the recording medium P held on the support 12 are out of focus, and proper image exposure with the two light beams L cannot be performed.

  On the other hand, in the present invention, the light beam La and the light beam Lb are made to coincide with each other so that the beam spots incident on the recording medium P held on the support 12 coincide with each other. At least one of the first light source unit 14a and the second light source unit 14b is incident on the polarization beam splitter 16 in accordance with the converging position shift (the amount) of the two light beams La and Lb due to the high-speed rotation of the deflecting unit. The light beam is a light beam that converges or diverges so as to correct (compensate) the deviation of the condensing position.

Specifically, in the exposure apparatus 10 shown in the drawing, first, in advance, experiments and simulations are performed in advance to find out the condensing position deviation of the light beam La and the light beam Lb caused by the distortion of the prism mirror 64 due to high-speed rotation. .
Further, in at least one of the light source unit 30a and the light source unit 30b, the condensing position of the light beam L is in the opposite direction (due to the distortion of the prism mirror 64) by the amount of the condensing position deviation found (for example, arrow a in FIG. 7). The light beam incident on the polarization beam splitter 16 is a convergent or divergent light beam so that it is shifted in the direction opposite to the condensing position shift.

More specifically, after knowing the converging position deviation a of the light beam La and the light beam Lb in the actual exposure apparatus 10, as an example, as conceptually shown in FIG. 4, from the light source units 30a and 30b. Using an imaging lens (dummy lens 70) that forms an optically equivalent optical system up to the scanning position (the surface of the recording medium P held by the support 12), the optically equivalent to the exposure apparatus 10 is used. An optical system (dummy optical system) is formed.
Then, the distance b between the light source 31 and the collimator lens 32 of at least one of the light source unit 30a and the light source unit 30b (only the light source unit 30b in FIG. 4) is adjusted so that the light beam L is not parallel light. As the light beam L that converges or diverges slightly, the condensing position deviation of the light beam in the dummy optical system is opposite to the condensing position deviation that was previously known by the amount of the condensing position deviation a of the light beam L that was previously found. Move in the direction. Further, the light source units 30 a and 30 b adjusted as described above are incorporated in the exposure apparatus 10.

In the present invention, in this way, in at least one of the first light source unit 14a and the second light source unit 14b, the light beam L is condensed at a high speed by the light deflecting unit such as the prism mirror 64. The converged or diverging light beam L is incident on the polarization beam splitter 16 so as to correct the condensing position deviation.
Therefore, the condensing positions of the two light beams La and Lb are aligned and incident on the recording medium P held by the support 12 regardless of the converging position of the light beam L due to the high-speed rotation of the light deflecting means. The beam spot diameters of the two light beams La and Lb can be made uniform, and accurate and appropriate scanning exposure with the two light beams L can be stably performed in the exposure apparatus using the inner drum.

In the exposure apparatus 10 of the illustrated example, the prism mirror 64 is rotated at high speed by adjusting the distance between the light source 31 of the light source unit 30 and the collimator lens 32 in at least one of the first light source unit 14a and the second light source unit 14b. The light beam L that converges or diverges is incident on the polarization beam splitter 16 in accordance with the condensing position deviation caused by the.
However, the present invention is not limited to this, and a light beam that converges or diverges according to a converging position shift caused by high-speed rotation of the prism mirror 64 is incident on the polarization beam splitter 16 by various means. be able to.

An example is shown in FIG.
The inner drum exposure device 72 shown in FIG. 5 (hereinafter referred to as the exposure device 72) basically has the same configuration as the exposure device 10 except that the relay lens 76 is included. The same reference numerals are given, and the following description mainly focuses on different parts.

In the inner drum exposure apparatus 72 shown in FIG. 5, the light source unit 30 is a normal light source unit that emits parallel light without adjusting the distance between the light source 31 and the collimator lens 32 as described above.
In this example, as conceptually shown in FIG. 5, at least one of the first light source unit 74a and the second light source unit 74b (in the illustrated example, provided only in the second light source unit 74b), the light beam By inserting a relay lens 76 in which L is a light beam that converges or diverges according to the condensing position deviation caused by the high-speed rotation of the prism mirror 64, the condensing position deviation is reduced according to the condensing position deviation. The light beam L that converges or diverges to be corrected is incident on the polarization beam splitter 16.

Also in this example, similarly to the previous exposure apparatus 10, in the actual exposure apparatus 72, the condensing position deviation a of the light beam caused by the high-speed rotation of the prism mirror 64 is found by experiments and simulations.
Then, as conceptually shown in FIG. 6, a dummy optical system that is optically equivalent to the light source unit 30 to the scanning position is formed using the dummy lens 70. Further, the light beam is adjusted so that the condensing position of the light beam L in this dummy optical system is shifted opposite to the converging position deviation previously known, by the amount of the condensing position deviation a of the light beam L previously known. The relay lens 76 is selected so as to converge or diverge, or the distance between the relay lenses 76 is adjusted. Then, the relay lens 76 is inserted into the corresponding light source unit of the first light source unit 74a or the second light source unit 74b of the exposure apparatus 72.

Hereinafter, the operation of the exposure apparatus 10 shown in FIG. 1 will be described.
When the recording medium P is loaded on the cylindrical inner surface of the support 12, image data to be recorded is supplied to the control means 26, and when an instruction to start recording is issued in response to an input instruction by the operator, the spinner 24. Rotates the prism mirror 64 (the quarter-wave plate 60 and the beam displacer 62) at a predetermined speed, and scanning means (not shown) causes the condenser lens 22 and the spinner 24 to move in the sub-scanning direction at a predetermined sub-scanning speed. (The extending direction of the center line of the cylindrical inner surface of the support).

When the position of the spinner 24 reaches a predetermined position, the control unit 24 independently modulates and drives the light sources 31 of the light source unit 30a and the light source unit 30b according to the image to be recorded on the recording medium P, The light source unit 30a emits the light beam La modulated according to the recorded image, and the light source unit 30b emits the light beam Lb modulated according to the recorded image.
As described above, the light beam L emitted from each light source unit is a p-polarized linearly polarized light beam with respect to the polarizing beam splitter 16.

In the first light source unit 14a, the light beam La emitted from the light source unit 30a is parallel-shifted in the optical path by the parallel plate and enters the polarization beam splitter 16 with p-polarized light.
On the other hand, in the second light source unit 14b, the traveling direction of the light beam Lb emitted from the light source unit 30b is adjusted by the first prism 34 and the second prism 36, and the polarization direction is rotated by the half-wave plate, The light beam splitter 16 is s-polarized light.

The linearly polarized light beams La and Lb incident on the polarization beam splitter 16 and having polarization directions orthogonal to each other are combined in the polarization beam splitter 16 and apparently become one light beam L. The light travels with the center line of the inner surface aligned with the optical axis, and then enters the quarter-wave plate 20.
The light beams La and Lb are converted by the quarter wavelength plate 20 from linearly polarized light beams whose polarization directions are orthogonal to circularly polarized light beams L whose rotation directions are opposite to each other, and are collected by the condenser lens 22. And enters the spinner 24.

The light beam L incident on the spinner 24 is first returned to the linearly polarized light beam L whose polarization directions are orthogonal to each other by the second quarter-wave plate 60, and then the extraordinary ray Pe by the beam displacer 62. The components corresponding to are shifted in parallel, split into two light beams La and Lb, and enter the prism mirror 64.
The light beams La and Lb incident on the prism mirror 64 are deflected (reflected) on the inner surface of the support 12 by the rotating prism mirror 64 and scanned in the main scanning direction (the circumferential direction of the cylindrical inner surface of the support 12). Incident on the recording medium P. Further, since the condenser lens 22 and the spinner 24 are moved in the sub scanning direction by the scanning means, the recording medium P is two-dimensionally scanned and exposed by the light beams La and Lb deflected in the main scanning direction. The

  Here, in the exposure apparatus 10, at least one of the light beams La and Lb incident on the polarization beam splitter 16 converges so as to correct this according to the converging position shift caused by the high-speed rotation of the prism mirror 64. Since the light beam L diverges, the focus position of the light beam incident on the recording medium P is the same in the optical axis direction, and appropriate image exposure is performed by two light beams modulated independently of each other. Can be done.

  Although the inner drum exposure apparatus of the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and various improvements and modifications may be made without departing from the scope of the present invention. Of course.

For example, although both the exposure apparatus 10 and the exposure apparatus 50 shown in the drawing use the beam displacer 62 made of a uniaxial crystal as a separating element for the combined light beam, the present invention is not limited to this. Instead, various known light beam separating elements that separate the light beam into a plurality of light beams, such as a Wollaston prism, a Rochon prism, and a Senalmon prism, can be used.
Further, in the illustrated example, only one of the light source units is a light beam that is incident on the polarization beam splitter (combining means) in accordance with the converging position deviation of the light beam caused by the high-speed rotation of the prism mirror (optical deflector). However, the present invention is not limited to this, and the light beams emitted from both light source units are converged or diverged so as to correct the converging position deviation due to the high-speed rotation of the light deflecting means. It may be divergent.

It is a conceptual diagram of an example of the inner drum exposure apparatus of this invention. It is a figure which shows notionally the light source unit of the inner drum exposure apparatus shown in FIG. It is a conceptual diagram for demonstrating the beam displacer used with the inner drum exposure apparatus shown in FIG. It is a conceptual diagram for demonstrating the manufacturing method of the inner drum exposure apparatus shown in FIG. It is a conceptual diagram of another example of the inner drum exposure apparatus of this invention. It is a conceptual diagram for demonstrating the manufacturing method of the inner drum exposure apparatus shown in FIG. It is a conceptual diagram of an example of the conventional inner drum exposure apparatus. It is a conceptual diagram for demonstrating the condensing position shift of the light beam in the conventional inner drum exposure apparatus.

Explanation of symbols

10, 72, 200 (Inner drum) Exposure device 12, 204 Support 14a, 14b, 74a, 74b Light source unit 16, 208 Polarizing beam splitter 18 Beam alignment optical system 20, 212 1/4 wavelength plate 22, 214 Condensing Lens 24, 216 Spinner 30, 30a, 30b, 202a, 202b Light source unit 31 Light source 32 Collimator lens 33 Parallel plate 34 First prism 36 Second prism 38 1/2 wavelength plate 50 Beam splitter 52 Lens 54 Beam position detector (PSD) )
60, 220 Second quarter wave plate 62, 222 Beam displacer 64 Prism mirror 66, 226 Motor 70 Dummy lens 224 Spinner mirror 228 Holder

Claims (4)

A first light source unit that emits a linearly polarized light beam; and a second light source unit that emits a linearly polarized light beam in a direction orthogonal to the light beam emitted by the first light source unit;
Multiplexing means for combining the light beams emitted from the first light source unit and the second light source unit;
A first polarizing member that converts the light beam combined by the combining means into two circularly polarized light beams whose rotation directions are opposite to each other;
A support having an arc-shaped inner peripheral surface and holding a recording medium on the inner peripheral surface;
A deflecting surface for reflecting the light beam toward the inner peripheral surface of the support; and rotating the deflecting surface about a center line of the inner peripheral surface of the support; Light deflecting means having a cubic prism mirror that scans in the main scanning direction that coincides with the circumferential direction of the inner peripheral surface of
A condensing optical system for condensing the circularly polarized light beam at a predetermined position;
An optical path adjusting means for causing the light beam to enter the light deflecting means in a predetermined path traveling along the central axis of the inner peripheral surface of the support;
The circularly polarized light beam, which is arranged on the optical path of the light beam adjusted by the optical path adjusting means and rotated integrally with the light polarizing means, is returned to two linearly polarized light beams orthogonal to each other. Two polarizing members;
A combined beam separating unit that rotates integrally with the light polarizing unit, separates the light beam converted into linearly polarized light by the second polarizing member into two light beams traveling in parallel;
A scanning unit that integrally moves the condensing optical system, the light deflecting unit, the second polarizing member, and the combined beam separating unit in the direction of the central axis of the inner peripheral surface of the support;
In addition, at least one of the first light source unit and the second light source unit emits a converged or divergent light beam so as to correct a light beam condensing position shift caused by rotation of the cubic prism mirror. Inner drum exposure device characterized.   The inner drum exposure apparatus according to claim 1, wherein at least one of the first light source unit and the second light source unit emits a light beam that converges or diverges so as to correct the converging position shift.   The at least one of the first light source unit and the second light source unit includes a relay lens that converges or diverges parallel light, and emits a light beam that converges or diverges so as to correct the converging position shift. 2. An inner drum exposure apparatus according to 1.   The inner drum exposure apparatus according to any one of claims 1 to 3, wherein a second polarization unit and a combined beam separation unit are fixed to the light deflection unit.

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