JP2005338512A - Method and apparatus for light beam scanning - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for light beam scanning in which scanning deformation is not generated and a light beam is continuously utilized during the time of reciprocal motion of a micromirror (reciprocal scanning with light beam). <P>SOLUTION: A plurality of laser beams are made incident on one micromirror, the irradiated positions (A, B) of the respective reflected laser beams are dislocated in a subscanning direction on a photoreceptor, and the used laser beams are controlled in time division during a main scanning of one line in a recording time (B1, A1, B2, A2). The distances (d1, d2)between adjacent main scanning line ends are approximately the same, the positional dislocation in the subscanning direction does not occur, and the dislocation in the subscanning direction at the scanning beginning position and the scanning terminating position of main scanning one line substantially does not occur. Thus, the laser beam is continuously utilized during the time of reciprocal motion of the micromirror (reciprocal scanning with laser beam). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light beam scanning method and apparatus for scanning a light beam reflected by a rotating micromirror.

  In a laser scanner head type laser printer, light from a laser light source is converted into parallel light by a collimator lens, and the polygon mirror is rotated to scan the parallel laser light on the photosensitive member to the print width. The printing speed in such a laser printer is defined by the number of rotations of the polygon mirror for scanning and the number of mirror surfaces, but there is a limit to speeding up due to mechanical limitations.

  In recent years, as a light beam scanning mechanism, development of a laser printer using a micro mirror (micro oscillating mirror element) which is a small-sized mirror instead of a polygon mirror has been developed. A micromirror is a mechanical element that reflects light using MEMS (Micro Electro Mechanical System) technology that applies various technologies in semiconductor manufacturing processes to reduce the size of various mechanical elements. The micromirror is driven by an electrostatic force and changes the reflection path of light depending on its rotation angle. Therefore, the micromirror is suitable as a light beam scanning mechanism, and a system for scanning a light beam using a micromirror. Has been developed (see, for example, Patent Document 1).

FIG. 8 is a diagram showing a configuration of a conventional light beam scanning apparatus using micromirrors. A laser light source 22 that emits laser light and a collimator lens 23 that collimates the laser light from the laser light source 22 are disposed on the light incident side of the micromirror 21. On the light reflecting side of the micromirror 21, a main lens 25 and a reflecting plate 26 for forming an image on the photosensitive member 24 rotating in a predetermined direction are disposed. Then, the parallel laser beam through the collimator lens 23 is irradiated onto the micromirror 21, and the micromirror 21 is rotated so that the irradiated laser beam is scanned on the surface of the photoconductor 24 to the print width.
Japanese Patent Laid-Open No. 11-305159

  FIG. 9 is a diagram showing the relationship between the rotation angle of the micromirror and the scanning trajectory of the laser beam in the conventional light beam scanning apparatus. The laser beam is scanned in a reciprocating manner in a curved line similar to a sine curve. The central part (solid line part in the figure) excluding both end parts (broken line part in the figure) in such laser beam scanning is scanned on the photosensitive member.

  When the light beam scanning device is used in a recording device such as a laser printer, in order to increase the speed of the recording process, the scanning process is performed efficiently, that is, the laser beam scanning according to the reciprocating rotation of the mirror is performed. It is conceivable to record image data using both reciprocating motions. That is, both the laser beam scanning in one direction (laser beam scanning from left to right in FIG. 6) and the laser beam scanning in the other direction (laser beam scanning from right to left in FIG. 6) are respectively performed in the main scanning direction. It is conceivable to record image data for each scanning line. However, in this case, the distances (d1, d2) between the main scanning line ends adjacent in the sub-scanning direction are largely shifted alternately (d1> d2), and scanning distortion occurs.

  Therefore, at present, only one-direction laser beam scanning is used for the recording process. Conventionally, there is a problem that the utilization efficiency of laser beam scanning is poor. In order to cope with the poor utilization efficiency of the laser beam scanning, it is conceivable to increase the recording processing speed by increasing the drive clock. However, for this purpose, an expensive CPU is required, resulting in an increase in cost. In addition, it is difficult to control the laser beam in accordance with the image data, and there is a limit to the speeding up. Therefore, improvement in utilization efficiency of the laser beam scanning is desired.

  The present invention has been made in view of such circumstances, and by using a plurality of light beams in a time-sharing manner during the scanning of one line, the micromirrors can be rotated back and forth (scanning light) without causing scanning distortion. An object of the present invention is to provide a light beam scanning method and a light beam scanning apparatus capable of continuously using a light beam during reciprocating scanning of the beam.

  Another object of the present invention is to provide a light beam scanning apparatus that can easily perform time-division control of a plurality of light beams.

  The light beam scanning method of the present invention is a light beam scanning method in which a light beam is scanned on a surface to be scanned by rotating a micromirror, and a plurality of light beams having different scanning positions on the surface to be scanned are used. The plurality of light beams are used in a time-sharing manner several times during a single scan.

  The light beam scanning device of the present invention is a light beam scanning device that scans a light beam on a surface to be scanned by rotating a micromirror, and an emission unit that emits a plurality of light beams having different scanning positions on the surface to be scanned; And control means for controlling the emission of each of the plurality of light beams by the emission means in a time division manner during one scan on the surface to be scanned.

  In the present invention, a plurality of light beams having different scanning positions on the surface to be scanned (photosensitive member) are used, and they are in one scan (one line in the main scanning direction) on the surface to be scanned (photosensitive member). Are used in a time-sharing manner. Therefore, even if the light beam is continuously used during the reciprocating rotation of the micromirror (reciprocating scanning of the light beam), the conventional scanning distortion does not occur. As a result, a high-speed writing operation on the surface to be scanned (photosensitive member) becomes possible.

  In the light beam scanning apparatus of the present invention, the emission means includes a plurality of light sources each emitting one light beam, and the control means is configured to perform the plurality of light sources during one scan on the scanned surface. The light beam emission in each is controlled in a time-sharing manner.

  In the present invention, light beam emission from a plurality of light sources each emitting one light beam in one scan (one line in the main scanning direction) on the surface to be scanned (photosensitive member) is time-shared. Control. Therefore, time division control of a plurality of light beams can be easily performed.

  In the present invention, since a plurality of light beams having different scanning positions on the surface to be scanned are used in a time-sharing manner during one scan on the surface to be scanned, the conventional scanning distortion does not occur. The light beam can be used continuously during the reciprocating rotation of the micromirror (reciprocating scanning of the light beam), and high-speed writing on the surface to be scanned can be performed without increasing the cost.

  In the present invention, since light beam emission from a plurality of light sources each emitting one light beam is controlled in a time division manner, time division control of a plurality of light beams can be easily performed.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. First, the concept of the present invention will be described.

  In the present invention, a plurality of light beams (laser beams) are incident on one micromirror, and each reflected laser beam is shifted on the photosensitive member (projection surface) so that its irradiation position is shifted in the sub-scanning direction. When scanning one line in the main scanning direction, the laser beam to be used is controlled in a time-sharing manner, and the positional deviation (scanning distortion) in the sub-scanning direction which has occurred in the conventional example using one laser beam. I am trying to correct it.

  FIG. 1 is a diagram showing the relationship between the rotation angle of a micromirror and the scanning trajectory of laser light in the present invention. In the example shown in FIG. 1, two laser beams are used, the scanning locus of the first laser beam is represented by A, and the scanning locus of the second laser beam is represented by B. As shown in FIG. 1, the second laser beam scanning position (irradiation position on the photoconductor) is slightly downstream in the sub-scanning direction (see FIG. 1) from the first laser beam scanning position (photographer irradiation position). 1 (lower side). Note that a central portion (a range in which the rotation angle of the micromirror is in the range of −25 ° to 25 °) excluding both end portions in the laser beam scanning is a region scanned on the photosensitive member.

Two laser beams whose irradiation positions are deviated in the sub-scanning direction are used by time-sharing control as follows when scanning one line in the main scanning direction.
From the start of scanning in one direction (left to right) (left end) (rotation angle: −25 °) to the middle line position (center) (rotation angle: 0 °):
Uses second laser beam (lower side) (solid line B1 in FIG. 1)
From one-way (left to right) line middle position (center) (rotation angle: 0 °) to end of scanning (right end) (rotation angle: 25 °):
Uses the first laser beam (upper side) (solid line A1 in FIG. 1)
From the start of scanning in the other direction (right to left) (right end) (rotation angle: 25 °) to the middle line position (center) (rotation angle: 0 °):
Uses second laser beam (lower side) (solid line B2 in FIG. 1)
From the line middle position (center) (rotation angle: 0 °) in the other direction (from right to left) to the end of scanning (left end) (rotation angle: −25 °):
Uses first laser beam (upper side) (solid line A2 in FIG. 1)

  In other words, in the present invention, the locus shown by the solid line in FIG. 1 is the scanning locus of the laser beam on the photosensitive member. In this case, the distance (d1, d2) between the main scanning line ends adjacent in the sub-scanning direction is small (d1≈d2), and scanning distortion does not occur. Further, there is almost no deviation in the sub-scanning direction between the scanning start position and the scanning end position in one main scanning line. Therefore, in the present invention, the laser beam can be continuously used during the reciprocating rotation of the micromirror (reciprocating scanning of the laser beam), and a high-speed writing operation to the photosensitive member can be realized.

(First embodiment)
FIG. 2 is a diagram showing the configuration of the light beam scanning apparatus according to the first embodiment of the present invention. The first embodiment is an example using two laser beams. On the light incident side of the micromirror 1, a collimator that collimates the laser beams from the two first laser light sources 2a, 2b, 2b, and 1b and 2b that emit laser beams. A lens 3 is provided. Further, on the light reflecting side of the micromirror 1, a main lens 5 and a reflecting plate 6 for forming an image on the photosensitive member 4 rotating in a predetermined direction are disposed. Then, two parallel laser beams through the collimator lens 3 are irradiated onto the micromirror 1, and the micromirror 1 is rotated so that the two irradiated laser beams are scanned on the surface of the photoconductor 4 to the print width. .

  In the first embodiment, the irradiation position of the laser beam emitted from the first laser light source 2a on the photosensitive member 4 and the irradiation position of the laser beam emitted from the second laser light source 2b on the photosensitive member 4 are: Specifically, the first and second laser light sources 2a and 2b are positioned so that the latter laser light is irradiated slightly downstream from the former laser light in the sub-scanning direction. .

  In addition to these optical members, the light beam scanning device rotates the micromirror 1 and the laser beam emission control unit 7 that controls the emission timing of the laser beams of the first and second laser light sources 2a and 2b. A rotation control unit 8 to be controlled and a synchronization circuit 9 that synchronizes both control operations of the laser light emission control unit 7 and the rotation control unit 8 are provided.

  FIG. 3 is a perspective view showing an example of the configuration of the micromirror 1. The micromirror 1 is manufactured by a microfabrication technique using anisotropic etching of silicon, and hinge bases 1b and 1c are formed on the silicon substrate 1a, and further on the hinge bases 1b and 1c. Further, hinges 1e and 1f for supporting the yoke 1d in a swingable manner are extended. By applying a voltage to the drive electrode (not shown), the yoke 1d serving as a reflection surface is rotated while being supported by the hinges 1e and 1f, thereby changing the reflection path of the laser beam and scanning the laser beam. To do.

  In the first embodiment, the laser beams from the first and second laser light sources 2a and 2b are time-division controlled as shown in FIG. 1 during scanning of one line in the main scanning direction. To use. The laser light from the first laser light source 2a corresponds to the first laser light (upper side) in FIG. 1, and the laser light from the second laser light source 2b corresponds to the second laser light (lower side) in FIG. . The laser light emission control unit 7 controls the laser light emission from each of the first and second laser light sources 2a and 2b while synchronizing the rotation operation of the micromirror 1 with the synchronization circuit 9 as described above. The two laser beams are time-division controlled.

  FIG. 4 is a diagram showing a simulation result of the rotation angle of the micromirror and the scanning trajectory of the laser light in the first embodiment using two laser lights. The conditions in this simulation result are: scanning area: 297 mm, photoreceptor width: 210 mm (A4 size), paper feed speed: 290 mm / sec. As a result, the distance between the main scanning line ends adjacent in the sub-scanning direction is Maximum: 52.39 μm, Minimum: 31.61 μm, Average: 42 μm. When the printing density is 600 dpi, the spot size of the laser beam on the photosensitive member is about 60 μm, and therefore, the line-to-line distance of about ± 10 μm has no problem in the recording process and can be said to be an acceptable range.

(Second Embodiment)
FIG. 5 is a diagram showing a configuration of a light beam scanning apparatus according to the second embodiment of the present invention. This second embodiment is an example using three laser beams. On the light incident side of the micromirror 1, three first laser light sources 2a, 2nd laser light sources 2b, and third laser light sources 2c that emit laser light are disposed. Other configurations are the same as those of the first embodiment described above, and the same or similar parts are denoted by the same reference numerals and description thereof is omitted.

  In the second embodiment, the irradiation position of the laser beam (first laser beam) emitted from the first laser light source 2a on the photosensitive member 4 and the laser beam (second laser beam emitted from the second laser light source 2b) The irradiation position of the laser beam) on the photosensitive member 4 and the irradiation position of the laser beam (third laser beam) emitted from the third laser light source 2c on the photosensitive member 4 are shifted in the sub-scanning direction. Specifically, the first laser beam, the second laser beam, and the third laser beam are irradiated in this order so that they are gradually shifted from the upstream side to the downstream side in the sub-scanning direction in this order. The three laser light sources 2a, 2b, 2c are positioned. Further, the laser beam emission control unit 7 synchronizes with the rotation operation of the micromirror 1 by the synchronization circuit 9, and the emission timing of each of the first, second, and third laser light sources 2a, 2b, and 2c. To control.

  In the second embodiment, the laser beams from the first, second, and third laser light sources 2a, 2b, and 2c are used while being time-division controlled when scanning one line in the main scanning direction. FIG. 6 is a diagram showing the relationship between the rotation angle of the micromirror and the scanning trajectory of the laser beam in the second embodiment. In FIG. 6, the scanning locus of the first laser light is represented by A, the scanning locus of the second laser light is represented by B, and the scanning locus of the third laser light is represented by C. As shown in FIG. 6, the scanning position of the first laser beam (irradiation position on the photoconductor), the scanning position of the second laser beam (irradiation position on the photoconductor), and the scanning position of the third laser beam ( The irradiation position on the photosensitive member) is gradually shifted from the upstream side in the sub-scanning direction to the downstream side in this order. As in FIG. 1, the central portion in the laser beam scanning (the range in which the rotation angle of the micromirror is −25 ° to 25 °) is an area scanned on the photosensitive member.

Three laser beams whose irradiation positions are shifted in the sub-scanning direction are used while being time-division controlled as follows during scanning of one line in the main scanning direction.
From the start of scanning in one direction (from left to right) (left end) (rotation angle: −25 °) to approximately one third of the line length (rotation angle: −10 °):
Uses third laser beam (lowermost side) (solid line C1 in FIG. 6)
From approximately 1/3 position (rotation angle: −10 °) to approximately 2/3 position (rotation angle: 10 °) of the line length in one direction (from left to right):
Uses second laser beam (center) (solid line B1 in FIG. 6)
From the position of approximately 2/3 of the line length in one direction (from left to right) (rotation angle: 10 °) to the end of scanning (right end) (rotation angle: 25 °):
Use the first laser beam (uppermost side) (solid line A1 in FIG. 6)
From the start of scanning in the other direction (right to left) (right end) (rotation angle: 25 °) to a position approximately 1/3 of the line length (rotation angle: 10 °):
Uses third laser beam (bottom side) (solid line C2 in FIG. 6)
From approximately 1/3 position (rotation angle: 10 °) of the line length in the other direction (from right to left) to approximately 2/3 position (rotation angle: −10 °):
Uses second laser beam (center) (solid line B2 in FIG. 6)
From the position (rotation angle: −10 °) of approximately 2/3 of the line length in the other direction (from right to left) to the end of scanning (left end) (rotation angle: −25 °):
Uses the first laser beam (uppermost side) (solid line A2 in FIG. 6)

  In the second embodiment, by performing time-sharing control of the three laser beams in this way, the distance (d1, d2) between the main scanning line ends adjacent in the sub-scanning direction is the same as in the first embodiment. The difference becomes small (d1≈d2), and scanning distortion does not occur. Further, there is almost no deviation in the sub-scanning direction between the scanning start position and the scanning end position in one main scanning line. Therefore, also in the second embodiment, the laser beam can be continuously used during the reciprocating rotation of the micromirror (reciprocating scanning of the laser beam), and a high-speed writing operation to the photosensitive member can be realized.

  FIG. 7 is a diagram showing simulation results of the rotation angle of the micromirror and the scanning trajectory of the laser beam in the second embodiment using three laser beams. The conditions in this simulation result are: scanning area: 297 mm, photoconductor width: 210 mm (A4 size), paper feed speed: 290 mm / sec. As a result, the distance between the main scanning line ends adjacent in the sub-scanning direction is Maximum: 48.89 μm, Minimum: 35.11 μm, Average: 42 μm. Compared with the first embodiment, the scanning distortion can be further reduced.

  In addition, although the example using two laser beams and the example using three laser beams were described, during scanning of one line in the main scanning direction using four or more laser beams, a plurality of them are used. Of course, the same effect can be obtained by time-sharing control of the laser beam. When the number of laser beams to be used is increased, the scanning distortion can be further reduced.

  In addition, although a plurality of separate laser light sources for emitting laser light are provided for each, an array type laser light source having a configuration in which a plurality of laser elements are integrated may be used. Further, the laser light emitted from one light source may be separated into a plurality of laser lights by a light separating member such as a beam splitter, and the plurality of separated laser lights may be used.

It is a figure which shows the relationship between the rotation angle of the micromirror in this invention (1st Embodiment), and the scanning locus | trajectory of a laser beam. It is a figure which shows the structure of the light beam scanning apparatus which concerns on 1st Embodiment. It is a perspective view which shows an example of a structure of a micromirror. It is a figure which shows the simulation result of the rotation angle of the micromirror in 1st Embodiment, and the scanning trace of a laser beam. It is a figure which shows the structure of the light beam scanning apparatus which concerns on 2nd Embodiment. It is a figure which shows the relationship between the rotation angle of the micromirror in 2nd Embodiment, and the scanning locus | trajectory of a laser beam. It is a figure which shows the simulation result of the rotation angle of the micromirror in 2nd Embodiment, and the scanning trace of a laser beam. It is a figure which shows the structure of the conventional light beam scanning apparatus. It is a figure which shows the relationship between the rotation angle of a micromirror in the conventional light beam scanning apparatus, and the scanning locus | trajectory of a laser beam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Micromirror 2a 1st laser light source 2b 2nd laser light source 2c 3rd laser light source 4 Photoconductor 7 Laser light emission control part 8 Rotation control part 9 Synchronous circuit

Claims (3)

  In a light beam scanning method of scanning a light beam on a surface to be scanned by rotating a micromirror, a plurality of light beams having different scanning positions on the surface to be scanned are used, and the scanning surface is scanned during a single scan. A light beam scanning method characterized by using a plurality of light beams by time-sharing several times.   In a light beam scanning apparatus that scans a light beam on a surface to be scanned by rotation of a micromirror, an emitting unit that emits a plurality of light beams having different scanning positions on the surface to be scanned, and a single time on the surface to be scanned A light beam scanning apparatus comprising: control means for controlling the emission of each of the plurality of light beams from the emission means in a time division manner during scanning. The emitting means includes a plurality of light sources each emitting one light beam, and the control means time-divides light beam emission from each of the plurality of light sources during one scan on the scanned surface. The light beam scanning apparatus according to claim 2, wherein the light beam scanning apparatus is controlled as follows.

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