JP2003149582A - Method and device for light beam scanning - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for light beam scanning, which make it possible to obtain an image of high quality with an inexpensive device by correcting deterioration in converged light spot shape due to a focus position shift of a light beam or an aberration of an optical system caused by various factors, or a spot position shift of the light beam by simple constitution. SOLUTION: The cylindrical internal surface of external surface of a sheet type scanned body is scanned with the light beam which is emitted by a light source and passed through the optical system, the wavefront of the light beam is controlled by a wavefront control element to correct at least one of the spot position shift of the light beam, the focus position shift of the light beam, and the aberration of the optical system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning method and device. More specifically, the present invention is directed to an error in the focal spot position due to the displacement of the spot position of the light beam, which is caused by various factors, and a focal spot displacement (defocus) of the light beam and deterioration of the focal spot shape due to the aberration of the optical system. The present invention relates to a light beam scanning method and apparatus using an optical scanning technique that corrects (blurring) and the like and realizes high-precision optical scanning, that is, high-quality image recording or high-precision image reading.

In particular, the present invention corrects at least one of a spot position shift of a light beam, a focus position shift of the light beam, and an aberration of an optical system, which are caused by various factors, in a cylindrical inner surface scanning type light beam scanning, BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical inner surface scanning type light beam scanning method and device using an optical scanning technique for performing high-quality image recording or high-accuracy image reading.

Further, according to the present invention, at least one of a light beam spot position shift, a light beam focus position shift, and an aberration of an optical system, which are caused by various factors, is corrected to realize highly accurate optical scanning. CTP (Computer to Plate), Imagesetter, DDCP (Direct Digital Color Proof)
er) and the like, which are preferably applicable to all optical recording heads, and a method and apparatus for scanning a cylindrical outer surface of a light beam using a light beam spot correction light scanning technique.

[0004]

2. Description of the Related Art A laser printer that guides a light beam of a laser or the like onto a recording medium by a scanning optical system and scans the recording medium to expose an image, or a laser beam that reads an image using the light beam. A light beam scanning device such as a reading device has been developed. This light beam scanning device includes a flat bed type that scans a flat recording medium with a laser beam and a cylindrical outer surface scanning type that scans a recording medium mounted on the outer peripheral surface of a rotating drum with a laser beam ( There are types such as an outer surface cylindrical type (outer drum type) and a cylindrical inner surface scanning type (inner surface cylindrical type (inner drum type)) that scans a recording medium mounted on the inner peripheral surface of the drum with a laser beam.

Of these, the inner-drum type light beam scanning device is often used because the recording medium is not peeled off during recording, the high-speed scanning property is excellent, and the quality of the recording light beam is high. Has been. FIG. 10 shows a conventional inner drum type light beam scanning device. As shown in FIG. 10, the inner drum type light beam scanning device 100 is
A drum 104 for mounting a recording medium (recording sheet) 102 on which an image or the like is recorded on an inner peripheral surface of a cylinder, a light source (laser beam generator) 106 for generating a laser beam L, and a concentric center axis of the drum 104. And a laser beam scanning unit 108 that scans the recording medium 102 with the laser beam L.

The laser beam scanning unit 108 includes a condenser lens 110 set on the same optical axis as the laser beam L and a reflecting surface set at an inclination angle of about 45 ° with respect to the incident direction of the laser beam L. It has an optical deflector (spinner) 112 and a motor 114 that drives the spinner 112 to rotate about the optical axis of the laser beam L. The laser beam L output from the laser beam generator 106 is condensed by the condenser lens 110, and then the motor 1
It is reflected by the reflecting surface of the spinner 112 which rotates at a high speed by 14 and is guided to the recording medium 102. At this time,
While the laser beam L scans (main scanning) the recording medium 102 while rotating at high speed by the rotating spinner 112, the laser beam scanning unit 108 moves in the direction indicated by arrow X in the drawing by a sub-scanning moving traverse (not shown). An image or the like is recorded on the recording medium 102 while being moved in the sub-scanning direction.

However, in the inner drum type light beam scanning device, when the spinner, which is a deflector, is rotated, its reflecting surface is distorted by centrifugal force, and the wavefront of the laser beam scanning the recording medium is distorted, so that the recorded image is recorded. There is a problem that the quality deteriorates. On the other hand, USP 5907153
Distortion of the laser beam caused by the distortion of the reflecting surface caused by the rotation of the spinner.
There is disclosed a technique for correcting a he reflected beam by using a transmission type or a reflection type “optical path length compensating device”.

That is, as shown in FIG. 11, in a light beam scanning type image recording apparatus, a laser beam generated from a laser diode 201 connected to a modulator 202 and passing through an optical level controller 203 is corrected by a correction element (compensation). Beam expander 205, resolution selector 2
06, the focus lens 207, etc., and then is reflected by the reflecting surface 210 of the rotating spinner 211 to form a cylinder 209.
The recording medium 208 mounted on the inner surface of the scanner is scanned to record an image or the like. At this time, the correction element 204 corrects aberrations or distortions caused by the rotation of the spinner 211.

The correction element 204, as shown in FIG.
An electrode 215 and a piezo element 214 are provided under a planar mirror 213, and further, an electrode 2 which is divided into 212 parts and is circumferentially arranged below the electrode 215 and the piezo element 214.
It has 16A-216L. Electrodes 215 and 21
6A to 216L, as shown in FIG.
9, controlled by microprocessor 218 and voltage source 620. Then, by controlling the electrodes 216A to 216L in synchronization with the rotation of the spinner 211, the piezoelectric element 214 is deformed, the mirror 213 is deformed, and the distortion of the laser beam caused by the spinner 211 is corrected.

On the other hand, as described above, as one of the light beam scanning devices, there is a cylindrical outer surface scanning type light beam scanning device. As described above, this is also called an outer drum type, which forms an image of a recording beam on a recording medium wound around the outer peripheral surface of a drum (recording drum) that rotates at a constant speed, and scans in the rotational axis direction of the drum. The optical system is moved in the sub-scanning direction to scan the recording medium with a light beam.

Conventionally, in an outer-drum type light beam scanning device, due to various factors such as the following, blurring due to spot position deviation of a recording light beam and aberration of an optical system,
It is known that the focus position of the recording light beam shifts and the image quality deteriorates. For example, due to eccentricity or distortion in the cylindrical direction that occurs during the manufacture of the drum, or variation in the thickness of the recording medium such as the plate or film wound around the drum outer surface, the spot of the light beam on the recording surface during one rotation of the drum. A position shift or a light beam focus position shift occurs. The recording of the light beam is also caused by distortion or flexure of the rail of the sub-scanning mechanism for sub-scanning the scanning optical system, flexure of the exposure surface plate, or sub-scanning feed speed error due to lead pitch error of the sub-scanning ball screw of the sub-scanning mechanism. A spot position shift occurs on the surface.

Further, the positional deviation of the recording beam that occurs when the spiral exposure is performed by using the multi-beam causes a graphic deviation. As described above, due to various factors, the recording beam spot position shift occurs, and the image quality such as figure accuracy is deteriorated. In the past, these were dealt with by highly accurate processing of each component such as the drum. However, there is no particularly effective measure.

In the case of CTP or the like, an aluminum plate is wound around the outer surface of the drum, but during rotation of the drum, the plate is pulled outward by centrifugal force, and the plate floats from the outer surface of the drum. A focus position shift occurs. Alternatively, when a minute dust is caught between the recording medium such as a plate or film wound around the drum outer surface and the drum outer surface, the recording medium floats from the drum outer surface at that location, and similarly the focal position shift occurs. further,
Since the rails of the sub-scanning mechanism (traverse) that moves the scanning optical system in the sub-scanning direction in the drum rotation direction are distorted or bent, a focal position shift occurs as the sub-scanning is performed.

Conventionally, such a focal position shift is corrected by moving the position of a lens system which forms an image of light emitted from a light source. For example, as shown in FIG. 14, a light beam emitted from a light source 300 is guided through a first lens group 302 and a second lens group 304 onto a recording medium 308 wound around an outer surface of a recording drum 306, and scanning exposure is performed. In the exposure apparatus, the second lens group 30
By moving No. 4 as indicated by the broken line in the figure, the focus position shift is corrected to correct the focus of the recorded image. Alternatively, as shown in FIG.
The focus position shift is corrected by moving the entire optical system including 0, the first lens group 302, and the second lens group 304.

[0015]

However, as shown in FIG.
In the inner drum type light beam scanning device shown in FIG. 15, the cause of deteriorating the quality of the recorded image or the figure accuracy of the image reading is not only the distortion of the laser beam but also the thick spot diameter, There are deterioration of the shape of the condensed spot such as collapse of the spot diameter, and displacement of the spot position of the light beam (that is, an error of the condensed spot position) in which the position of the dot for recording the image is displaced from the target position. The factors that cause the deterioration of the focused spot shape and the error of the focused spot position are not only those caused by the distortion of the rotating spinner as described above, but also those caused by the spinner, for example,
There are ones due to the focal position shift (defocus) of the light beam, and ones due to the aberration of the optical system. The one caused by the spinner is dynamic, while the one caused by the aberration of the optical system is static caused by a single lens or a combination of lenses. In addition, errors from the circularity of the drum (drum eccentricity, columnar error, etc.), deviation from the linearity of the traverse that moves in the sub-scan,
There are factors such as inconsistency (parallel shift or intersection) between the traverse movement direction and the drum center line, or variation in the thickness of the recording medium.

In short, the deterioration of the focused spot shape means that the spot diameter becomes thick or the spot shape becomes large due to the aberration of the focal position shift (defocus) of the laser beam in the optical axis direction (z direction) or the optical system. The error of the focused spot position is the deviation of the recording position of the laser beam on the recording medium (x and y directions). Conventionally, the deterioration of the focused spot shape caused by the above various factors (hereinafter, represented by the focus position shift of the light beam and the aberration of the optical system)
And, in order to avoid the error of the focused spot position (hereinafter, represented by the light beam spot position shift) and obtain a high-quality recorded image, it is necessary to rely on high-precision processing and high-precision adjustment. There is a problem that the cost of the device becomes expensive.

Further, in the outer drum type light beam scanning device shown in FIGS. 14 and 15, if the spot position deviation of the light beam is corrected by relying on highly accurate processing of the drum or the like, the product price will be high. There is a problem that it becomes a thing. Further, as described above, in the method of correcting the focal position shift of the light beam by moving the lens group or the like, the heavy lens group or the like is moved, so that high-speed response cannot be expected so much. It is extremely difficult to correct the focus position shift due to factors such as dust. Further, since the lens group is mechanically moved, the vibration generated thereby may adversely affect the recording accuracy. After all, in the past, in order to eliminate the spot position shift or the focus position shift of the light beam, it is necessary to process a member such as a drum with high precision and further add a device for removing dust and the like. There is a problem that it will lead to soaring.

The present invention has been made in view of the above-mentioned conventional problems, and is caused by various factors other than those caused by the spinner as described above, in particular, the focal position shift (defocus) of the light beam. ) Or a light beam scanning method and device capable of obtaining a high-quality image with an inexpensive device by correcting the deterioration of the condensed spot shape due to the aberration of the optical system and the spot position shift of the light beam with a simple configuration. The first object is to provide the method, and the second object is to provide the method and the apparatus for scanning the inner surface of the cylinder, to which the method and the apparatus for scanning the light beam are applied.

The present invention has been made in view of the above-mentioned conventional problems, and in addition to the first problem described above, the light beam generated on the recording surface due to various factors as described above is recorded. With respect to spot position shifts, light beam focus position shifts, and optical system aberrations, the mechanical movement of the lens itself and the height of members such as drums can be prevented without making the members such as drums highly accurate. Without precision processing
It is a third object to provide a cylindrical outer surface scanning type light beam scanning method and device which realizes a stable system by correcting an adverse effect such as vibration by an inexpensive device.

[0020]

In order to solve the above-mentioned first problem, the first aspect of the present invention is to scan a sheet-shaped object by a light beam emitted from a light source and passing through an optical system. In this case, the wavefront of the light beam is controlled by a wavefront control element to correct at least one of a spot position shift of the light beam, a focus position shift of the light beam, and an aberration of the optical system. A light beam scanning method is provided.

Here, in order to solve the above-mentioned second problem, a second aspect of the present invention is the above-mentioned main aspect, wherein the sheet-shaped object to be scanned is held on an inner peripheral surface of a cylinder. ,
It is preferable to provide a cylindrical inner surface scanning type light beam scanning method of scanning with a light beam emitted from the light source, passing through the optical system, and reflected and deflected by a rotary light deflector.

In order to solve the above-mentioned third problem, a third aspect of the present invention is the same as the above-mentioned first aspect.
A sheet-shaped object to be scanned is provided on a cylindrical outer surface scanning type light beam scanning method which is wound around an outer surface of a drum rotating at a constant speed, and is scanned by a light beam emitted from the light source and passing through the optical system. Is good.

Here, by controlling the power or distortion of the wavefront of the light beam emitted from the wavefront control element, at least one of the focal position shift of the light beam and the aberration of the optical system is corrected. preferable. Further, it is preferable to correct the spot position deviation of the light beam by controlling the inclination of the wavefront of the light beam emitted from the wavefront control element.

Further, the focal position shift of the light beam is corrected by controlling the power or distortion of the wavefront of the light beam emitted from the wavefront control element, and the wavefront of the light beam emitted from the wavefront control element. Of the correction of the aberration of the optical system by controlling the power or distortion of the optical system and the correction of the spot position deviation of the light beam by controlling the inclination of the wavefront of the light beam emitted from the wavefront control element. It is preferable to combine at least two or more corrections.

Further, the wavefront control element is preferably any one of a piezo type, an electrostrictive type, an electrostatic attractive type and a liquid crystal type. The wavefront control element has a plurality of electrodes arranged on the surface of the substrate and a deformable conductive film facing the electrodes and having a surface functioning as a reflecting surface, and a voltage is applied to the electrodes. It is preferable that the reflective surface is formed into a desired shape by causing electrostatic attraction to deform the conductive film.

Further, the sheet-shaped object to be scanned is a sheet-shaped recording medium, and the light beam is a recording light beam, and the sheet-shaped recording medium is two-dimensionally scanned by the recording light beam. Therefore, it is preferable to record an image on the sheet-shaped recording medium.

In order to solve the above first problem,
A fourth aspect of the present invention is a light source that emits a light beam, and an optical system that allows the light beam emitted from the light source to pass through.
A wavefront control element that controls the wavefront of the light beam to correct at least one of the spot position shift of the light beam, the focus position shift of the light beam, and the aberration of the optical system, and emits from the light source. A light beam scanning device is provided, which scans a sheet-shaped object to be scanned with the light beam that has passed through an optical system and is corrected by the wavefront control element.

In order to solve the above second problem,
A fifth aspect of the present invention is the light beam scanning device according to the fourth aspect, further comprising: a drum for holding the sheet-shaped object to be scanned on an inner peripheral surface of a cylinder thereof; A rotating light deflector for reflecting and deflecting a beam to scan the sheet-shaped object to be scanned, wherein the wavefront control element is installed upstream of the rotating light deflector in the traveling direction of the light beam. It is preferable to provide a cylindrical inner surface scanning type light beam scanning device characterized by the above.

In order to solve the above third problem,
A sixth aspect of the present invention is the light beam scanning device according to the fourth aspect, further comprising a drum around which the sheet-shaped recording medium is wound and which rotates at a constant speed. It is preferable to provide a light beam scanning device for scanning the outer surface of a cylinder.

Here, it is preferable that the wavefront control element controls the power or distortion of the wavefront of the emitted light beam to correct at least one of the focal position shift of the light beam and the aberration of the optical system. . Further, it is preferable that the wavefront control element controls the inclination of the wavefront of the emitted light beam to correct the spot position deviation of the light beam.

The wavefront control element corrects the focal position shift of the light beam by controlling the power or distortion of the wavefront of the emitted light beam, and controls the power or distortion of the wavefront of the emitted light beam. The correction of at least two of the correction of the aberration of the optical system and the correction of the spot position shift of the light beam by controlling the wavefront inclination of the emitted light beam are performed in combination. preferable.

Further, the wavefront control element is preferably any one of a piezo type, an electrostrictive type, an electrostatic attraction type and a liquid crystal type. The wavefront control element has a plurality of electrodes arranged on the surface of the substrate and a deformable conductive film facing the electrodes and having a surface functioning as a reflecting surface, and a voltage is applied to the electrodes. It is preferable that the reflective surface is formed into a desired shape by causing electrostatic attraction to deform the conductive film.

Further, the sheet-shaped object to be scanned is a sheet-shaped recording medium, and the light beam is a recording light beam, and the sheet-shaped recording medium is two-dimensionally scanned by the recording light beam. Therefore, it is preferable to record an image on the sheet-shaped recording medium.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION A light beam scanning method and apparatus according to the present invention will be described below in detail with reference to the preferred embodiments shown in the accompanying drawings. First, with reference to FIGS. 1 to 5, the cylindrical inner surface scanning light according to the second and fifth aspects of the present invention to which the light beam scanning method and device according to the first and fourth aspects of the present invention are applied. A beam scanning method and apparatus will be described.

FIG. 1 shows a cylindrical inner surface scanning type light beam scanning device (hereinafter, inner drum) according to a fifth embodiment of the present invention for carrying out the cylindrical inner surface scanning type light beam scanning method according to the second embodiment of the present invention. FIG. 3 is a conceptual diagram showing a schematic configuration of one embodiment of a type optical scanning device). It should be noted that the cylindrical inner surface scanning type light beam scanning device according to the fifth aspect of the present invention is the first embodiment of the present invention.
It goes without saying that this is an embodiment of the light beam scanning device according to the fourth aspect of the present invention, which carries out the light beam scanning method according to the above aspect.

In FIG. 1, an inner drum type optical scanning device 10 has three laser diodes 12a, 12b, 12c as light beam output means for outputting laser beams having substantially the same wavelength and substantially the same intensity. . Also,
The inner drum type optical scanning device 10 collimates the laser beams output from the laser diodes 12a, 12b, 12c and generates them as parallel light, so that the first collimating lenses 14a, 14b, 14c, and 2 as a light deflection element. -Dimensional acousto-optic device (AOD) 16a, 16b, 1
6c, AOD emission lenses 18a, 18b, 18c, zero-order light cut plates 20a, 20b, 20c and second collimating lenses 22a, 22b, 22c. Further, in order to combine the generated parallel light, the reflection mirror 2
4a, a polarization beam splitter 24b, and a beam splitter 24c are included in the combining optical system 24, whereby parallel light is combined into almost one laser beam.

The inner drum type optical scanning device 10 also includes a beam expander system 26 for expanding the beam diameter of the light beam combined with the substantially one laser beam.
28, an opening 30 for removing flare light, a mirror 32 for changing the direction of the light beam, a condenser lens 34 for condensing the light beam into spot light, and the condensed spot light on the inner surface of the drum 40. An optical deflector (spinner) 36 for rotating and scanning is provided on the recording sheet 42 which is the scanned object. Further, a traverse (sub-scanning transport system) 44 for moving the optical system such as the condenser lens 34 and the spinner 36 along the center line of the drum is provided.

The inner drum type optical scanning device 10 according to the present embodiment is, in addition to this, a feature of the present invention.
Various factors, especially deterioration of the focal position of the light beam (defocus) or deterioration of the focused spot shape of the light beam due to aberration of the optical system (blurring of the light beam) and spot shift of the light beam (error of the focused spot position) ) (Light beam spot position deviation) for correcting the wavefront control element (WF
C ... Wave Front Control (device)) 38. The wavefront control element 38, which will be described in detail later, controls the wavefront of the light beam, and is installed upstream of the optical deflector 36, preferably between the beam expander 28 and the condenser lens 34. . Particularly in the case of this embodiment,
As shown in FIG. 1, the wavefront control element 38 is installed between the mirror 32 and the condenser lens 34.

The wavefront control element 38 controls the wavefront of the light beam, and specifically, for example, a deformable mirror used in an astronomical telescope or the like can be used. This is to correct the distortion of the wave front by reflecting the light from the star with a mirror whose surface shape is deformed, for example, when the wave front is distorted by the fluctuation of the atmosphere. . As the deformable mirror (reflecting mirror type), for example, a face sheet mirror, a bimorph mirror, a split piston mirror, etc. are known. Further, as the wavefront control element 38, a transmission type element using a liquid crystal element can also be used.

The face sheet mirror is made by sticking thin mirror surfaces of glass or the like on a large number of actuators and moving the actuators separately to deform the mirror surfaces. As the actuator that deforms the mirror surface, a laminated piezo element, an electrostrictive element (PMN), an electrostatic attraction type (for example, manufactured by OKO Co., Ltd.) or the like can be considered. The bimorph mirror is configured such that a plurality of piezoelectric plates polarized in opposite directions are attached to each other and a voltage is applied to the plates to change the curvature of the mirror surface to deform the mirror surface. The split piston mirror is one in which the mirror surface is split and the tilt is independently controlled by the piston. Further, the transmission type using a liquid crystal element controls the wavefront by controlling the optical path length.

FIG. 2 shows a specific construction of an electrostatic attraction type wavefront control element (face sheet mirror) as an embodiment of the wavefront control element 38. The wavefront control element 38 shown in the figure has a plurality of microelectrodes 47 (47a, 47b, 47c, 47 in FIG. 2) two-dimensionally arranged on a substrate 46.
d and 47e) and a conductive film 48 formed of an aluminum thin film or the like, which is provided facing the microelectrode 47 with a certain distance therebetween and has a mirror surface to form a reflection surface, and controls the microelectrode 47. A voltage according to a control signal generated by the device 45 is applied, and an electrostatic attractive force is generated between the microelectrode 47 and the conductive film 48, so that the conductive film 4 serving as a reflective surface.
The shape of 8 is changed to a desired shape, and the reflection direction of the light beam L incident on the reflection surface is freely changed and deflected.

In the wavefront control element 38 of the illustrated example, for example, the control device 45 uniformly controls the minute electrodes 47 so that the inclination angle changes while maintaining the planar shape of the conductive film 48, and the reflection surface is changed. It can be tilted (tilted), or the microelectrodes 47 are individually controlled to make the conductive film 48.
It is also possible to give a predetermined curvature or a predetermined distortion to the surface shape of, that is, to give power or distortion to the reflecting surface. The wavefront control element having such a structure is a MEMS (Micro El
It is easy to manufacture by the technology of ectro Mechanical Systems), and can be obtained at a lower cost than expensive acousto-optic elements, piezo elements, or electro-optical elements.

In this embodiment, as described above, the wavefront control element 38 is provided in the optical path so that the focal spot of the light beam shifts or the aberration of the optical system deteriorates the focused spot shape of the light beam or the spot position of the light beam. The deviation is corrected. The causes of the deterioration of the focused spot shape due to the shift of the focal position of the light beam (hereinafter, also referred to as defocus) are as follows.
For example, an error from the circularity of the drum (drum eccentricity, cylindrical error, etc.), a linearity error of the sub-scanning moving traverse, a disagreement between the moving direction of the traverse and the drum center line (parallel shift, crossing), a photosensitive medium There are variations in thickness.

Here, the drum roundness error is as shown in FIG.
As shown in (a), when the drum is not a perfect circle C but a distorted circle C ', the deviation Δz from the perfect circle is referred to. That is, assuming that the drum is originally a perfect circle C, and the spot diameter is adjusted so as to record an image on it, if the drum is distorted like C ′, only the amount of deviation Δz will occur. The spot diameter deteriorates. Further, the columnar error is, as shown in FIG.
It is said that the radius of curvature r, r ′ varies depending on the location of the drum. Even in this case, if the same image recording is performed, the image shape is distorted. Further, the traverse linearity error means that the movement of the traverse 44 is not performed along a straight line but is a curve deviating from the straight line, and the disagreement between the moving direction of the traverse and the drum center line is The movement of the traverse 44 is performed along a straight line, but the direction is deviated from the drum center line.

With respect to the deterioration of the focused spot shape of the light beam due to defocus caused by these factors,
By applying power (refractive power (curvature of wavefront); quadratic function) to the action surface of the light beam, for example, the reflecting surface or the transmitting surface, to the wavefront controlling element 38, as a result, the wavefront controlling element 38 This can be corrected by controlling the power or distortion of the wavefront of the emitted light beam. The method of applying power to the wavefront control element 38 is not particularly limited, and the wavefront control element 3
The reflecting surface may be deformed by driving the actuator of No. 8 to change the refracting power or the curvature, or in the case of the transmission type, the refractive index may be changed by changing the internal molecular structure. .

Specifically, the focal length of the condenser lens 34 is set to f
= 280 mm, the beam luminous flux diameter is Φb = 30 mm, and the defocus on the recording surface is Δz = 100 μm. The wavefront control element 38 has a diameter (major axis) in the direction of the line of intersection of the plane formed by the incident light Li and the reflected light Lo and the reflection surface of the wavefront control element 38, as indicated by the diagonal lines in FIG. It has an elliptical shape with a diameter (minor axis) in the direction orthogonal to Φms.

At this time, when the incident angle of the light beam on the wavefront control element 38 is θ, Φmt = Φms / cos θ = Φb / cos
It is desirable to set θ. Further, as shown by the broken line in FIG. 4, the wavefront control element 38 is deformed into a shape in which the cuts in the major axis direction and the minor axis direction of the diagonal ellipse are both part of a circle. At this time, the deformation amount Δd of the central portion necessary for the correction of the defocus is Δd = 0.1 μm. In this way, by deforming the reflecting surface of the wavefront control element 38, the wavefront of the light beam controlled by the wavefront control element 38 has power, so that the defocus can be corrected.

As for the correction of the deterioration of the shape of the condensed spot due to the aberration of the optical system, for example, the astigmatism where the condensing position of the ray bundle emitted from the off-axis object point of the optical system does not match on the sagittal plane and the tangential plane. The aberration is corrected by controlling the amount of power in the vertical and horizontal directions of the reflecting surface of the wavefront control element 38. Further, for example, in the case of coma aberration caused by the spinner 36 rotating to distort the cross-sectional shape of its reflecting surface into a cubic curve, the action surface (reflecting surface) of the wavefront control element 38 is adjusted according to the shape. It is only necessary to correct the power or distortion of the wavefront of the light beam emitted from the wavefront control element 38 by giving distortion (function of third or higher order) to the (or transmission surface).

The factors causing the deviation of the spot position of the light beam include, for example, an error from the circularity of the drum (drum eccentricity, cylindrical error, etc.), a linearity error of the sub-scanning moving traverse, and a traverse moving direction. There are discrepancies with the drum centerline (parallel shifts, intersections), discrepancies between the incident light beam and the drum centerline, and so on. With respect to the displacement of the spot position of the light beam due to these factors, a tilt (tilt; linear function) is applied to the action surface of the wavefront control element 38, for example, the reflection surface or the transmission surface, and as a result, the wavefront is changed. Control element 3
By controlling the tilt of the wavefront of the light beam emitted from the wavefront control element 38, it is possible to correct this. Specifically, the focal length of the condenser lens 34 is f = 280 mm, and the beam luminous flux diameter is Φb = 30.
mm, the beam position error on the recording surface is Δx = 100
μm. That is, 1 on the recording sheet 42 in the x direction.
It is assumed that the displacement is 00 μm.

At this time, as shown in FIG. 5, the direction of the reflected light of the wavefront control element 38 must be changed by 0.36 mrad. As a result, the tilt amount (tilt angle) Δθ of the wavefront control element 38 required to correct the position error is Δθ = 0.
36/2 = 0.18 mrad. That is, in this case, the reflection surface (mirror surface) of the wavefront control element 38 is set to 0.18.
By tilting mrad, x on the recording sheet 42
It is possible to correct the deviation in the direction. Note that FIG. 5 conceptually shows the manner of correction, and the direction in which the wavefront control element 38 is tilted also changes depending on the direction of the positional deviation.

The above example describes a correction method for the case where the focal position shift (defocus) of the light beam or the focus spot shape deterioration due to the aberration of the optical system and the spot position shift of the light beam occur. However, these deteriorations and errors may occur at the same time. In that case, the wavefront of the light beam controlled by the wavefront control element 38 has power, and
At the same time, the tilt is controlled so that the tilt is corrected.
For example, by tilting the mirror surface of the wavefront control element 38 while deforming it, it is possible to correct each of them simultaneously. In this way, two or three of these correction operations can be combined and corrected.

The above-mentioned control of the wavefront control element 38 is performed in synchronization with the rotation of the spinner 36.
This is done, for example, by electrically controlling an actuator that controls the reflective surface of the wavefront control element 38. Further, the error amount of each of the above errors (focal position shift and spot position shift) is measured in advance and held as a table so that the wavefront control element 38 is controlled. Alternatively, the output image may be measured to calculate the error amount, and the error amount may be corrected accordingly.

In the example described above, the error from the roundness of the drum (drum eccentricity, cylindrical error, etc.), the linearity error of the sub-scanning moving traverse, the traverse moving direction and the drum center line do not match. Deterioration of the focused spot shape of the light beam (focal position shift and aberration of the optical system) and spot shift caused by factors such as (parallel shift, crossing) and the like are emitted from the wavefront control element by the wavefront control element 38. The correction is performed by controlling the power or distortion of the wavefront of the light beam to be generated, or by controlling the tilt of the wavefront of the light beam.
Distortion of the light beam due to distortion of the reflection surface of the
may also be similarly corrected by controlling the wavefront by the wavefront control element 38.

As described in detail above, according to the present aspect, the wavefront control element can prevent the deviation of the focal position of the light beam due to various error factors, the deterioration of the focused spot shape due to the aberration of the optical system, or the deviation of the spot position of the light beam. Since the correction is performed by the method, the image quality in image recording and image reading can be improved. Also, since the tolerance of each error (positional deviation and aberration) can be relaxed,
The processing cost and the adjustment cost can be suppressed, and the device cost can be reduced.

Next, referring to FIGS. 6 to 9, the cylinders according to the third and sixth aspects of the present invention to which the light beam scanning method and device according to the first and fourth aspects of the present invention are applied. An outer surface scanning type light beam scanning method and apparatus will be described.

FIG. 6 shows a cylindrical outer surface scanning type light beam scanning device (hereinafter referred to as an outer drum type) of a sixth embodiment of the present invention for carrying out the cylindrical inner surface scanning type light beam scanning method according to the third embodiment of the present invention. 1 is a schematic configuration diagram showing a first embodiment of an optical scanning device). The first embodiment corrects the spot position deviation of the light beam caused by various factors by controlling the tilt of the wavefront of the light beam emitted from the wavefront control element by the wavefront control element. The cylindrical outer surface scanning type light beam scanning device according to the sixth aspect of the present invention implements the light beam scanning method according to the first aspect of the present invention, and the light beam scanning according to the fourth aspect of the present invention. It goes without saying that this is an embodiment of the device.
As shown in FIG. 6, the outer drum type optical scanning device 50 of the first embodiment comprises a light source 52, a first lens group 54, a wavefront control element 56, a second lens group 58 and a recording drum (drum) 60. A recording medium 62, which is a sheet-shaped object to be scanned, is wound around the outer peripheral surface of the drum 60.

In the outer drum type optical scanning device 50 of this embodiment, the light beam emitted from the light source 52 is reflected by the wavefront control element 56 through the first lens group 54, and the
The recording medium 62 on the drum 60 is exposed through the lens group 58 to record an image.

As the light source 52, various light sources corresponding to the spectral sensitivity of the target recording medium can be used as long as they can emit a sufficient amount of light. For example, if the recording medium is a commonly used PS plate (conventional PS plate) that can be exposed to ultraviolet light, an ultra-high pressure mercury lamp or a metal halide lamp may be used. In addition, for heat mode plates that are sensitive to infrared light, infrared Broa
A d area Laser Diode or the like may be used. In addition, a halogen lamp, a xenon lamp, a two-dimensional array light source (LED), etc. can be used according to the recording medium.

The first lens group 54 includes a collimator lens and collimates the light beam emitted from the light source 52 into parallel light. The second lens group 58 includes a condenser lens (focusing lens), narrows the beam diameter of the light beam, and forms an image as spot light on the recording medium 62 wound around the outer surface of the drum 60. It is a thing. The wavefront control element 56 controls the wavefront of the light beam by changing the tilt (inclination), power (refractive power), distortion, etc. of the reflection surface (wavefront) thereof. Then, this wavefront control element 56
Is used to control the tilt of the wavefront of the emitted light beam to correct the spot position deviation of the light beam.

The wavefront control element 56 controls the wavefront of the light beam by changing its tilt, power, distortion, etc., and is the same as the wavefront control element 28 used in the above-mentioned second and sixth aspects. Since the same one may be used, detailed description thereof will be omitted.

In this embodiment, as described above, the wavefront control element 56 capable of controlling the wavefront of the light beam is provided between the first lens group 54 and the second lens group 58, and the light beam is controlled by various factors. The spot position deviation is corrected. As a factor of the spot position shift of the light beam, as described above, for example, eccentricity or distortion in the drum cylindrical direction that occurs during the manufacturing of the drum, or the thickness variation of the recording medium such as a plate or film wound around the drum outer peripheral surface, Distortion or bending of the rail of the sub-scanning mechanism for sub-scanning the scanning optical system, bending of the exposure surface plate, or sub-scanning feed speed error due to lead pitch error of the sub-scanning ball screw of the sub-scanning mechanism may be considered. Further, the figure shift also occurs due to the position shift of the recording beam that occurs when the spiral exposure is performed using the multi-beam.

When the spot position shift of the light beam, that is, the shift of the position to be recorded on the recording surface (shift in the xy directions on the recording surface) occurs due to these various factors, the wavefront control element 56 causes Correct this. Specifically, by tilting (tilting) the light beam acting surface of the wavefront control element 56, that is, the mirror surface in the illustrated example, the displacement of the spot position of the light beam is corrected. For example, by tilting the wavefront control element 56 at the position shown by the solid line in FIG. 6 to the position shown by the broken line,
The position of the light beam focused on the recording medium 62 is corrected from that shown by the solid line to that shown by the broken line.

At this time, the relationship between the amount of displacement of the spot position on the recording surface and the amount of tilt (angle of inclination) of the wavefront control element 56 is that the amount of positional displacement that occurs during recording is actually recorded on the recording medium in advance. It suffices to measure and calculate the tilt amount for this, and give this to the driver of the wavefront control element 56. As a result, the driver of the wavefront control element 56 is driven so that the tilt amount is synchronized with various spot position shift amounts existing in the recording surface, and the wavefront control element 5 is driven.
By controlling 6, it is possible to correct the spot position shift due to various factors.

As described above, according to this embodiment, in the outer drum type optical scanning device, it is possible to correct the spot position deviation of the light beam caused by various factors,
Thereby, stable image quality of the exposure apparatus itself can be secured. Further, since the processing accuracy of the drum, which may be a factor that causes the displacement of the spot position of the light beam, is not so required, the processing accuracy of the drum and other various members can be lowered, and as a result, the price of the apparatus can be reduced. It can be cheaper. That is, by applying the present invention, it is possible to easily correct the spot position deviation of the light beam with a less expensive device, and it is possible to obtain high-quality image quality.

Next, a second embodiment of the sixth aspect of the present invention will be described. In the present embodiment, the present invention is applied to the same outer drum type optical scanning device (exposure device) as the above-described first embodiment as a light beam scanning device,
The wavefront control element controls the power of the wavefront of the light beam emitted from the wavefront control element to correct the focal position shift of the light beam caused by various factors.

FIG. 7 shows the outer drum type optical scanning device 50 of the present embodiment. Since this is the same as that of the first embodiment shown in FIG. 6, a detailed description of the device configuration will be omitted. . The present embodiment differs from the first embodiment in the method of controlling the wavefront control element 56. That is, in the present embodiment, power (refractive power) is applied to the wavefront control element 56 to correct the focal position shift of the light beam.

Factors causing the focal position shift of the light beam are as follows:
As described above, for example, the eccentricity or distortion in the drum cylindrical direction that occurs during the manufacture of the drum, the lift of the aluminum plate from the outer surface of the drum due to the centrifugal force during the rotation of the drum in the case of CTP, and the recording wound on the outer surface of the drum. It is conceivable that the recording medium floats up due to the inclusion of minute dust between the medium and the outer surface of the drum, or the rail of the sub-scanning mechanism is distorted or bent. When a shift in the focal position of the light beam, that is, a shift (Δz) in the direction of the optical axis (z direction perpendicular to the xy directions on the recording surface) occurs due to these various factors, this is caused by the wavefront control element 56. To correct.

By controlling the power (eg, curvature) of the wavefront of the wavefront control element 56 and controlling the power of the wavefront of the light beam emitted from this element, the focal position shift of the light beam is corrected. At this time, the method of controlling the power of the wavefront by the wavefront control element 56 is not particularly limited. For example, when the wavefront control element 56 is initially flat as shown by the solid line in FIG. 7, the wavefront control element 56 is controlled by a wavefront control element driver (not shown),
As shown by the broken line in FIG. 7, the refractive index may be changed by deforming the shape into a curved surface. Alternatively, as in the case where the wavefront control element 56 is a liquid crystal type, the refractive index may be changed by changing the internal molecular arrangement without changing its shape.

As described above, by using the wavefront control element, the focal position shift caused by various factors in the outer drum type optical scanning device is corrected, so that the stable image quality of the optical scanning device (exposure device) itself is corrected. Can be secured. Further, since the processing accuracy of the drum and the processing accuracy of other various members are not so required, it is possible to realize a more inexpensive device. Furthermore, since there is no mechanical movement of a heavy lens or the like, extra vibration can be suppressed and the drive current can be reduced.

In correcting the focal position shift of the light beam by the wavefront control element 56, the detection of the focal position shift of the light beam is performed by previously scanning the recording medium to obtain the data, and the data is obtained. The wavefront control element 56 may be controlled based on In particular, in the case of system-specific factors such as eccentricity of the drum and distortion of the rail of the sub-scanning mechanism, such data is obtained in advance and input to the wavefront control element driver. The method of controlling by using is effective. In addition, when the recording medium is lifted due to trapping dust or the like, the position where the focal position shift occurs is different each time, so feedback is performed by detecting with a sensor in the method described below. It suffices that the correction is made in real time.

Next, a third embodiment of the sixth aspect of the present invention will be described. The third embodiment is the same as the first lens group 54 in the first embodiment or the second embodiment described above.
And the wavefront control element 56 provided between the second lens group 58 and
With respect to the above, the arrangement of the wavefront control element 56 and the second lens group 58 is set to a more preferable arrangement, and only the focal position is moved with almost no change in the beam diameter so that the focal position shift of the light beam is corrected. It is the one. That is, as shown in FIG. 8, the outer drum type optical scanning device 51 of the third embodiment includes a light source 52 and a first lens group 5.
4, the second lens group 58, the recording drum 60, and the wavefront control element 56 between the first lens group 54 and the second lens group 58.
The configuration including the above is the same as that of the first or second embodiment, except that the wavefront control element 56 and the second lens group 5 are provided.
The arrangement as described below has been devised so that the arrangement with 8 is a preferable arrangement.

As described above, the wavefront control element 56 is a varifocal system which can change its refractive index (curvature of the working surface) by changing the power, and as a result, can change the focal length. . On the other hand, the second lens group 58 is
The focal length is constant and it is a fixed focus system. At this time,
Rear principal point 56a of the wavefront control element 56 which is a variable focus system
And the front principal point 58 of the second lens group 58, which is a fixed focus system.
Let d be the distance from a. Further, the front focal length of the second lens group 58 is f.

Here, regarding the wavefront control element 56 and the second lens group 58, the distance d between the principal points is determined by the second lens group 5
8 to be equal to the front focal length f, that is, d =
It is arranged so as to be f. That is, the rear principal point 56a of the wavefront control element 56, which is a varifocal system, is located at the second lens group 5
8 so as to match the front focal position of the wavefront control element 56.
Then, the second lens group 58 is arranged.

By arranging the wavefront control element 56 and the second lens group 58 in this way, the beam diameter of the light beam focused on the recording medium 62 by the second lens group 58 is hardly changed, and Only the focus position can be moved. Therefore, with the configuration of the first embodiment or the second embodiment, particularly by arranging as in the third embodiment, more excellent effects can be obtained.

Next, a fourth embodiment of the sixth aspect of the present invention will be described. In the fourth embodiment, a sensor is provided, the distance between the scanning optical system and the recording surface is measured, and a factor of focus position deviation such as floating of the recording medium due to dust or the like is detected, and the wavefront control element is accordingly detected. By controlling
It is intended to correct the focus position shift in real time, and realizes autofocusing by feeding back the detection result of the sensor.

FIG. 9 is a plan view schematically showing the outer drum type optical scanning device of this embodiment. As shown in FIG. 9, the outer drum type optical scanning device 70 of the present embodiment uses an exposure head 72 equipped with an optical system such as a wavefront control element.
Although the recording medium 76 wound around the recording drum 74 is scanned, the exposure head 7 is provided near the exposure head 72.
A recording surface distance sensor 78 for measuring the distance from 2 to the recording surface of the recording medium 76 is provided. The exposure head 72 and the recording surface distance sensor 78 are both moved by a sub-scanning moving mechanism (not shown) on the sub-scanning rail 80 in a direction parallel to the rotation axis of the recording drum 74 as indicated by an arrow in the figure. .
Further, the measurement signal of the recording surface distance sensor 78 is input to a computer (control means) 82, and the computer 82 controls the wavefront control element based on this. The computer 82 controls not only the wavefront control element but also the entire apparatus such as the rotation of the drum, the sub-scanning moving mechanism and the image data.

The exposure head 72 receives a light beam emitted from a light source (not shown), focuses the light beam on the recording surface for exposure, and moves on the sub-scanning rail 80 so that the recording surface is exposed. The image is exposed two-dimensionally. In addition,
As the exposure head 72, an optical system including the wavefront control element 56 in the outer drum type optical scanning devices 50 and 51 shown in FIGS. 6 to 8 mounted on, for example, an optical surface plate can be used. The recording surface distance sensor 78 measures the distance to the recording surface at least at a position slightly before the exposure position of the exposure head 72 in the sub-scanning direction. The measurement result is sent to the computer 82, and the computer 82 analyzes the result.

When the measured distance is not a constant value but a different value is detected by the computer 82, for example, when almost the same value is sent, but when a smaller value than before is received, recording is performed. When it is determined that the surface is lifted for some reason, and the position is exposed by the exposure head 72, the wavefront control element is controlled in synchronization with it to correct the focus position. Also, for example, the recording drum 7
Even if the diameter of 6 varies depending on the location, it is possible to always match the focus position on the recording surface by detecting it by the measurement signal and controlling the wavefront control element accordingly.

As described above, by feeding back the measured value by the sensor and controlling the wavefront control element based on this, not only the factors caused by the device itself but also abruptly caused by dust etc. It is possible to easily correct the occurrence of the focal position shift due to various factors. Further, by correcting the focus position shift at high speed in this way, the influence of dust or the like can be removed, and the stability of image quality can be ensured. In this way, complete autofocusing can be achieved.

Further, although the spot position deviation correction and the focus position deviation correction of the recording light beam of each of the embodiments of the present aspect described above may be performed independently, these two corrections are performed simultaneously. In this way, the spot position shift and the focus position shift of the recording light beam may be simultaneously corrected. That is, in this case, power may be applied to the wavefront of the wavefront control element and the wavefront may be tilted. Further, also in this aspect, similarly to the second and fifth aspects of the present invention, the aberration of the optical system may be corrected by imparting power and distortion to the wavefront of the wavefront control element, In addition to the aberration of the optical system, the deviation of the focal position of the light beam may be corrected. Further, in addition to these, by tilting the wavefront of the wavefront control element, the deviation of the spot position of the light beam is also corrected. You may do it.

In each of the above embodiments of each aspect of the present invention, a light beam recording device (image exposure device) that exposes a sheet-like recording medium with a light beam is described as an example of the light beam scanning device. The present invention can also be applied to a light beam reading device (image reading device) that reads an image or the like from an image bearing medium using a light beam such as a laser beam.

Although the light beam scanning method and apparatus of the present invention have been described in detail above with reference to various embodiments, the present invention is not limited to the above-described various embodiments, and the present invention is not limited thereto. Within the scope of the gist,
Of course, various improvements and design changes may be made.

[0083]

As described above in detail, according to the first and fourth aspects of the present invention, the focal position shift (defocus) of the light beam caused by various factors or the aberration caused by the aberration of the optical system occurs. Deterioration of the light spot shape and spot displacement of the light beam can be corrected with a simple configuration.
It is possible to obtain a high quality image with an inexpensive device.

Further, as described in detail above, according to the second and fifth aspects of the present invention, in the light beam scanning of the cylindrical inner surface scanning type, the above effect, that is, the light beam generated by various factors Deterioration of the focused spot shape due to defocusing of the focal point or aberration of the optical system and spot deviation of the light beam can be corrected with a simple configuration, and a high-quality image can be obtained with an inexpensive device. it can.

As described above in detail, according to the third and sixth aspects of the present invention, the light beam spot position deviation, the focus position deviation, and the aberration of the optical system are corrected using the wavefront control element. Therefore, it is possible to reduce the processing accuracy of the member such as the drum, and in the light beam scanning of the cylindrical outer surface scanning type, the spot position shift, the focus position shift, and the aberration of the optical system caused by various factors, It can be easily corrected by a cheaper device, and since there is no mechanical movement of a heavy lens or the like, it is possible to suppress extra vibration and reduce the drive current.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a schematic configuration of an embodiment of an inner drum type light beam scanning device according to a fifth aspect of the present invention.

FIG. 2 is a schematic cross-sectional view of an example of a wavefront control element used in the inner drum type scanning device shown in FIG.

3A is an explanatory diagram showing eccentricity of the drum, and FIG. 3B is an explanatory diagram showing a cylindrical error of the drum.

FIG. 4 is an explanatory diagram showing a state in which power is applied to the wavefront control element.

FIG. 5 is an explanatory diagram showing how a tilt is applied to the wavefront control element.

FIG. 6 is a schematic configuration diagram showing a first embodiment of an outer drum type light beam scanning device according to a sixth aspect of the present invention.

FIG. 7 is a schematic configuration diagram showing a second embodiment of an outer drum type light beam scanning device according to the sixth aspect of the present invention.

FIG. 8 is a schematic configuration diagram showing a third embodiment of an outer drum type light beam scanning device according to the sixth aspect of the present invention.

FIG. 9 is a plan view showing a schematic configuration of a fourth embodiment of an outer drum type light beam scanning device according to a sixth aspect of the present invention.

FIG. 10 is a perspective view showing an outline of a conventional inner drum type light beam scanning device.

FIG. 11 is a block diagram showing an outline of an inner drum type optical beam scanning device that corrects a beam wavefront distortion caused by a conventional spinner.

12 is a configuration diagram showing an outline of the correction element of FIG.

FIG. 13 is a plan view showing the correction element of FIG.

FIG. 14 is a schematic configuration diagram showing an example of a conventional outer drum type light beam scanning device.

FIG. 15 is also a schematic configuration diagram showing another example of a conventional outer drum type light beam scanning device.

[Explanation of symbols]

10 Inner surface cylindrical optical scanning device 12a, 12b, 12c Laser diode 14a, 14b, 14c First collimating lens 16a, 16b, 16c Two-dimensional acousto-optic device (AO
D) 18a, 18b, 18c AOD emission lenses 20a, 20b, 20c 0th order light cut plates 22a, 22b, 22c Second collimating lens 24 Combined optical system 24a Total reflection mirror 24b Polarization beam splitter 24c Beam splitters 26, 28 Beam extractor Panda (system) 30 Aperture 32 Mirror 34 Condenser lens 36 Optical deflector (spinner) 38 Wavefront control element 40 Drum 42 Recording sheet 44 Traverse (sub scanning means) 45 Control device 46 Substrate 47, 47a, 47b, 47c, 47d , 47e Microelectrode 48 Conductive films 50, 51, 70 Cylindrical outer surface scanning optical scanning device 52 Light source 54 First lens group 56 Wavefront control element 56a Rear principal point of wavefront control element 58 Second lens group 58a Of second lens group Front principal points 60, 64 (recording) drums 62, 66 recording medium 72 dew Optical head 78 Recording surface distance sensor 80 Sub-scanning rail 82 Computer

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2C362 AA31 AA36 AA47 AA48 AA49                       BA87 BB28 BB46                 2H041 AA23 AB12 AB38 AC06 AC08                       AC10 AZ06                 2H045 AG09 CB00 CB22 DA41                 5C051 AA02 CA07 DB22 DB24 DB30                       DC04 DE09 DE23                 5C072 AA03 CA06 DA02 DA04 DA20                       DA21 HA02 HA06 HA14 HA16                       HB15 JA02 RA12

Claims (18)

[Claims] 1. When scanning a sheet-shaped object to be scanned by a light beam emitted from a light source and passing through an optical system, a wavefront control element controls the wavefront of the light beam to shift the spot position of the light beam, A method of scanning a light beam, wherein at least one of a focus position shift of the light beam and an aberration of the optical system is corrected. 2. The sheet-shaped object to be scanned is held by an inner peripheral surface of a cylinder, and is scanned by a light beam emitted from the light source, passing through the optical system, and reflected and deflected by a rotary light deflector. The cylindrical inner surface scanning type light beam scanning method according to claim 1. 3. The cylinder according to claim 1, wherein the sheet-shaped object to be scanned is wound around an outer surface of a drum that rotates at a constant speed, emitted from the light source, and scanned by a light beam that has passed through the optical system. External scanning type light beam scanning method. 4. By controlling the power or distortion of the wavefront of the light beam emitted from the wavefront control element,
The light beam scanning method according to claim 1, wherein at least one of a focal position shift of the light beam and an aberration of the optical system is corrected. 5. The light beam scanning according to claim 1, wherein the spot position deviation of the light beam is corrected by controlling the inclination of the wave front of the light beam emitted from the wave front control element. Method. 6. A correction of focus position deviation of the light beam by controlling the power or distortion of the wavefront of the light beam emitted from the wavefront control element, and the wavefront of the light beam emitted from the wavefront control element. Of the correction of the aberration of the optical system by controlling the power or distortion of the optical system and the correction of the spot position deviation of the light beam by controlling the inclination of the wavefront of the light beam emitted from the wavefront control element. The light beam scanning method according to claim 1, wherein at least two or more corrections are combined. 7. The light beam scanning method according to claim 1, wherein the wavefront control element is one of a piezoelectric type, an electrostrictive type, an electrostatic attractive type and a liquid crystal type. 8. The wavefront control element includes a plurality of electrodes arranged on a substrate surface, and a deformable conductive film which faces these electrodes and whose surface functions as a reflecting surface. The light beam scanning method according to claim 1, wherein the reflective surface is formed into a desired shape by applying a voltage to generate an electrostatic attractive force and deforming the conductive film. 9. The sheet-shaped object to be scanned is a sheet-shaped recording medium, the light beam is a recording light beam, and the sheet-shaped recording medium is two-dimensionally scanned by the recording light beam. 9. The light beam scanning method according to claim 1, wherein an image is recorded on the sheet-shaped recording medium. 10. A light source that emits a light beam, an optical system that passes the light beam emitted from the light source, a wavefront of the light beam is controlled, and a spot position shift of the light beam And a wavefront control element that corrects at least one of a focus position shift and an aberration of the optical system, the sheet beam is emitted from the light source, passes through the optical system, and is corrected by the wavefront control element. A light beam scanning device for scanning an object to be scanned. 11. The light beam scanning device according to claim 10, further comprising: a drum that holds the sheet-shaped object to be scanned on an inner peripheral surface of the cylinder, and the light beam is reflected and deflected by rotating the drum. And a rotating light deflector for scanning the sheet-shaped object to be scanned, wherein the wavefront control element is installed upstream of the rotating light deflector in the traveling direction of the light beam. A cylindrical inner surface scanning type light beam scanning device. 12. The optical beam scanning device according to claim 10, further comprising a drum around which the sheet-shaped recording medium is wound and which rotates at a constant speed. Light beam scanning device. 13. The wavefront control element controls power or distortion of a wavefront of the emitted light beam to correct at least one of a focal position shift of the light beam and an aberration of the optical system. 13. The light beam scanning device according to any one of 12. 14. The light beam scanning device according to claim 10, wherein the wavefront control element controls the inclination of the wavefront of the emitted light beam to correct the spot position deviation of the light beam. . 15. The wavefront control element corrects the focal position shift of the light beam by controlling the power or distortion of the wavefront of the emitted light beam, and controls the power or distortion of the wavefront of the emitted light beam. At least two of the correction of the aberration of the optical system by the correction and the correction of the spot position shift of the light beam by controlling the inclination of the wavefront of the emitted light beam are performed in combination. The light beam scanning device according to any one of 10 to 14. 16. The light beam scanning device according to claim 10, wherein the wavefront control element is one of a piezo type, an electrostrictive type, an electrostatic attractive type and a liquid crystal type. 17. The wavefront control element includes a plurality of electrodes arranged on the surface of a substrate, and a deformable conductive film which faces these electrodes and whose surface functions as a reflection surface. The light beam scanning device according to claim 10, wherein the reflective surface is formed into a desired shape by applying a voltage to generate an electrostatic attractive force and deforming the conductive film. 18. The sheet-shaped scanned body is a sheet-shaped recording medium, and the light beam is a recording light beam,
18. The light beam scanning device according to claim 10, wherein an image is recorded on the sheet-shaped recording medium by two-dimensionally scanning the sheet-shaped recording medium with the recording light beam.