KR20070030833A - Multilaser bi-directional printer with an oscillating scanning mirror - Google Patents

Abstract

A system and method for generating data lines (96, 98) on a photosensitive medium (88) for use in a display or printing device. Data lines 96 and 98 are generated by two or more coordinated parallel laser light beams 14A and 14B directed by resonant pivoting torsionally hinged mirror 90. The pivoting mirror 90 sweeps the two adjusted light beams 14A, 14B back and forth across the photosensitive medium 88 to provide bidirectional printing. The relative motion between the plane of the swept light beam and the photosensitive medium is to move the photosensitive medium 88 when used in a printing device or to move the sweeping plane of the light beams 14A, 14B vertically when used in a display device. It is also provided by.

Display, printing device, photosensitive media, resonant pivoting, torsional hinge, mirror, equidistant parallel light beams, front and rear sweeping, bidirectional printing, vertical motion

Description

MULTILASER BI-DIRECTIONAL PRINTER WITH AN OSCILLATING SCANNING MIRROR}

FIELD OF THE INVENTION The present invention generally relates to torsional hinge mirrors of a fevering micro-electric mechanical systems (MEMS), including scanning mirrors operating at a resonant frequency, and more particularly, to multiple laser beams and bidirectional. It is about using these mirrors for printing.

background

Rotating polygonal scanning mirrors are typically used in laser printers to provide a "raster" scan of an image of a laser light source across a moving photosensitive medium, such as a rotating drum. Such systems allow the rotation of the photosensitive drum and rotating polygon mirror to be synchronized such that the light beam (laser beam) sweeps or scans in one direction across the rotating drum as the facet of the polygon mirror rotates through the laser beam. To be. Subsequent facets of the rotating polygon mirror generate similar scans or sweeps that also traverse the rotating photosensitive drum but provide image lines that are spaced apart or displaced from the preceding image line by a certain distance. Increasing the rotational speed of polygon mirrors involves a much greater cost increase, so printer manufacturers using polygon mirrors as drive engines are most often equidistantly oriented or reflected from a single facet of polygon mirrors. Use two or four parallel lasers spaced apart.

There have also been prior art attempts to provide scanning beams using cheaper flat mirrors with a single reflective surface. Instead of a rotating polygon mirror, for example, a dual axis or single axis scanning mirror may be used to generate the beam sweep or scan. The rotating photosensitive drum and the scanning mirror are synchronized as the drum rotates in the forward direction, so that on the medium, a printed image line parallel to the beam scan or sweep generated by the pivoting mirror and perpendicular to the movement of the photosensitive medium Generates.

However, in the case of single axis mirrors, the return sweep will traverse the trajectory on the moving photosensitive drum which is inclined with respect to the printed image line resulting from the preceding or forward sweep. Thus, the use of a single axis resonant mirror according to the prior art is that as the mirror forms a return sweep or completes its period, the modulation of the reflected light beam is interrupted and then the beam starts scanning in the original direction. When it is turned on again. Using only one of the sweep directions of the mirror, of course, slows the print speed. Thus, in order to effectively use a scanning mirror to provide bidirectional printing, the prior art is directed to a sweep plane that is also perpendicular to the scan so that mirror sweeps in each direction produce images that are always parallel to the movable or rotating photosensitive drum. Attempt bi-directional scanning that needs to be controlled. Realizing such parallel lines requires continuous vertical adjustment of the sweeping beam, which can be realized by using a dual axis torsion mirror or a pair of single axis torsion mirrors. However, at very high print speeds, it has been found that both forward and reverse sweeps of a single axis mirror can be used, and vertical adjustment is unnecessary.

Texas Instruments currently manufactures torsional dual axis and single axis pivoting MEMS mirrors that are processed from one sheet of material (such as silicon, for example), typically about 115-125 microns thick. The dual axis layout can consist of a mirror surface supported on a gimbal frame, for example by two silicon torsional hinges, while in the case of a single axis device the mirror is by a pair of torsional hinges. Is directly supported. While elliptical forms with a long axis of about 4.0 mm and a short axis of about 1.5 mm are particularly useful, the mirror can be of any desired shape. This elongated elliptical mirror is matched in its shape at the angle at which the light beam is received. The gimbal frame used by the dual axis mirror is attached to the support frame by another set of torsional hinges.

Texas Instruments also manufactures single axis mirrors with two layers of silicon and magnets. The multilayer mirror makes it possible to select the most effective torsional hinge while reducing the flexibility or bending of the mirror surface at high vibration speeds.

These mirrors, manufactured by Texas Instruments, are particularly suitable for use as scanning engines for high speed laser printers and visual displays.

According to the prior art, torsional hinge mirrors initially interact with small magnets mounted on the pivoting mirror in a vertical position away from the pivoting axis for oscillating the mirror or generating a sweeping motion of the beam. It was driven directly by them. In a similar manner, the vertical movement of the beam sweep is also controlled by magnetic coils that interact with the magnets mounted on the frames of the gimbals at positions perpendicular to the axis used to pivot the frames of the gimbals. Inexpensive and reliable magnetic drives may be used and set in such a way that the pivoting device maintains its resonant frequency. Furthermore, the reflective surface of the scanning mirror can be almost any shape, including squares, circles, ellipses, etc., but it has been found that elongated elliptical shapes are particularly suitable.

Summary of the Invention

These and other problems are generally solved or circumvented by preferred embodiments of the present invention that provide methods and apparatuses for generating data lines on photosensitive media, such as rotating drums for printers or screens for display systems. In other words, technical advantages are generally realized.

According to embodiments of the invention, a reflective surface, such as a torsionally hinged mirror, is directed onto a reflective surface that oscillates around the first pivot axis and in which a number of coordinated parallel light beams vibrate. Next, in order to sweep the plurality of light beams back and forth across the photosensitive medium in the forward and reverse directions, a plurality of coordinated parallel light beams are reflected from the vibrating reflective surface. The relative vertical movement between the forward and reverse direction of the swept light beams and the photosensitive medium, if used in a printer, is provided by a movable medium such as a rotating drum. However, in the case of a display device, the swept light beams are typically moved by moving a group of beams perpendicular to the direction of the swept beam. This movement can be realized by using a dual axis mirror or, alternatively, by providing a vertical movement using a second mirror. As a number of coordinated parallel light beams sweep across the photosensitive medium, a plurality of selected data lines are generated on the photosensitive medium.

According to another embodiment, as the multiple light beams sweep across the photosensitive medium in forward direction, a plurality of selected data lines are generated, and as the multiple light beams sweep across the photosensitive medium in reverse direction, the same plurality of selected data The lines are generated again. However, each of the plurality of light beams provides one of a plurality of selected data lines, in the reverse direction, different from what they provided in the forward direction. In order to realize proper line spacing in the printed page or display, multiple or "N" adjusted parallel light beams are spaced at equal intervals from each other by a distance "S", and one complete During the back and forth cycle, the relative vertical movement between the photosensitive medium and the swept light beam is equal to the distance S × N.

According to yet another embodiment, two light beams are used such that as the first and second light beams move forward across the photosensitive medium, a first data line is generated with the first of the two light beams and two A second data line is generated with the second of the light beams. Next, as the first and second light beams move in opposite directions across the photosensitive medium, the second data line is generated again with the first light beam and the first data line is generated again with the second light beam.

According to yet another embodiment, the plurality of light beams comprises a first light beam, a second light beam, a third light beam and a fourth light beam, and thus, as the light beams sweep forward across the photosensitive medium, the first and second light beams. First, second, third and fourth selected data lines are generated, respectively, with the third and fourth light beams, and as the light beams sweep in the opposite direction across the photosensitive medium, the first, second, Third and fourth selected data lines are generated second with third, fourth, first and second light beams, respectively.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description thereof that follows may be better understood. In the following, further features and advantages of the invention will be described which form the subject of the claims of the invention. Those skilled in the art should appreciate that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention.

For a more complete understanding of the invention and its advantages, in the following, the following description is referred to in connection with the accompanying drawings.

1A, 1B, and 1C illustrate the use of a rotating polygon mirror to generate a sweep of a laser printer, according to the prior art.

2A, 2B and 2C are diagrams of embodiments of single axis torsional hinge pivoting devices having a mirror as a functional surface.

3A, 3B, 3C, and 3D illustrate one prior art example of generating a unidirectional beam sweep using a single axis flat scanning mirror.

4A and 4B show two examples of a dual axis mirror suitable for use in a laser printer or display.

5 illustrates one method of magnetically driving a resonant mirror using a pair of magnets.

6 illustrates a single magnet drive to provide resonant vibrations.

7 illustrates another embodiment of a single magnet drive.

8 is a perspective view of a single axis mirror, as illustrated in FIGS. 2A and 2B, for generating a beam sweep of a laser printer.

9 is a perspective view of a dual axis mirror aligned for use with a laser printer or laser display.

10 is a perspective view of a single axis mirror alignment for use in a laser printer or laser display.

11 illustrates the use of a prior art polygon mirror to reflect multiple parallel laser beams spaced at equal intervals.

12 illustrates the use of a torsionally hinged pivoting mirror to reflect multiple equally spaced parallel laser beams.

13A and 13B show patterns of two and four coordinated bidirectional laser beams spaced at equal intervals, respectively, generated on the photosensitive medium;

14 is a graph illustrating line intensity at scan center and scan edge in accordance with the teachings of the present invention.

Detailed Description of Exemplary Embodiments

In the following, the construction and use of presently preferred embodiments are discussed in detail. However, it should be understood that the present invention provides a number of applicable invention concepts that can be implemented in a wide variety of specific contexts. The specific embodiments discussed are merely examples of specific methods for constructing and using the present invention.

Those skilled in the art will recognize many possible applications and variations of the present invention based on the following examples of possible embodiments of the present invention. FIELD OF THE INVENTION The present invention relates to high speed pivoting reflective surfaces or mirrors and is particularly suitable for providing raster scans to laser printers and displays. More specifically, the present invention relates to a high speed resonant pivoting mirror around a pair of torsional hinges used to reflect multiple parallel laser beams spaced at equal intervals.

Referring now to FIGS. 1A, 1B and 1C, the operation of a prior art printer using a rotating polygon mirror is illustrated. As shown in FIG. 1A, there is a rotating polygonal mirror 10 with eight reflective surfaces l0a-10h. The light source 12 is a light beam 14a, such as a laser beam, which is focused on the rotating polygonal mirror such that the light beam from the light source 12 is blocked by the facets 10a-10h of the rotating polygonal mirror 10. ). Thus, the laser light beam from the light source 12, indicated by reference numeral 14a, has, as illustrated by the dotted line 14b, from the facets 10a-10h of the polygon mirror 10, having a rotation axis 20. Reflected by a moving photosensitive medium 16, such as a rotating photosensitive drum 18. The moving photosensitive medium 16 or drum 18 rotates around the axis 20 in the direction indicated by the bow-shaped arrow 22, so that the moving photosensitive medium 16 is exposed to the reflected light beam 14b. Or the area of the drum 18 continues to vary. As shown in FIG. 1A, the polygon mirror 10 is about an axis 24 (perpendicular to the drawing in this respect), as indicated by the second bowed arrow 26. To rotate. Thus, the leading edge 28 of the rotating polygon mirror 10 facet 10b blocks the laser light beam 14a from the light source 12 and directs the light beam to the photosensitive medium, as indicated at 14b. It will be appreciated that this will be the first portion of facet 10b to reflect. As the mirror 10 rotates, each of the eight facets of the mirror 10 will in turn block the light beam 14a and reflect the light beam 14b. As will be appreciated by those skilled in the art, optics for focusing the light beam, lens system for flattening the focal plane towards the photosensitive drum, and any fold for changing the direction of the scanned beam. Fold mirrors have been omitted for ease of understanding.

Below the rotating polygon mirror 10 is illustrated a second view of the photosensitive medium 16 or drum 18 as seen from the polygon scanner. As shown by photosensitive drum view 18, immediately after facet 10b blocks light beam 14a and reflects it to moving photosensitive medium 16 or drum 18, the drum 18. There is a starting point 30 of the laser beam 14b image.

Referring now to FIG. 1B, except that the rotating polygon mirror 10 continues its rotation about the axis 24 such that the facet 10b is rotated, ending its blocking of the laser beam 14a. An arrangement substantially identical to that illustrated in FIG. 1A is shown. As will be appreciated by those skilled in the art, due to the variable angle of the mirror facets provided to the light beam 14a being blocked, the reflected light beam 14b is shown as arrows 32 and dashed lines 34 in FIG. 1B. As it will, it will move across the surface of the rotating drum.

However, since the rotating drum 18 is moving vertically with respect to the scanning movement of the light beam 14b, if the rotating shaft 24 of the rotating mirror is exactly perpendicular to the axis 20 of the rotating photosensitive drum 18, It will also be appreciated that the image of the swept or scanning light beam will be recorded at a slight tilt. As shown more clearly as the bottom view of the photosensitive drum 18, the dotted line 34 illustrates that the trajectory of the light beam 14b itself is slightly inclined, while the solid line 36 representing the resulting image on the photosensitive drum. ) Is not tilted and is perpendicular to the rotation or movement of the photosensitive medium 16. In order to realize this parallel printed line image 36, the axis of rotation 24 of the polygonal mirror 10 is typically mounted slightly inclined with respect to the rotating photosensitive drum 18, thus sweeping across the medium 16. Alternatively, the amount of vertical travel or distance moved along the vertical axis 38 by the light beam 14B during the scan is equal to the amount of movement or rotation of the photosensitive medium 16 or drum 18. Alternatively, if necessary, this tilt may be realized using a tilted fold mirror.

1C illustrates that facet 10b of rotating polygonal mirror 10 has been rotated from light beam 14a and facet 10c has blocked the light beam. As such, the process is repeated for the second image line. Due to the continuous rotation, of course, each facet of the rotating mirror 10 blocks the light beam 14a so that it is spaced apart at regular intervals, such as image line 36a, which together will form a line of print or other image. Will generate a series of parallel image lines.

Furthermore, one of ordinary skill in the laser printing industry will recognize that a rotating polygon mirror is a sophisticated and expensive part or component that must rotate at high speeds, even with slower printers, without excessive wear of bearings. Accordingly, flat resonant mirrors of less complex torsional hinges are rapidly gaining adoption.

2A and 2B illustrate monolayer single axis torsion mirror devices. Each of the devices of FIGS. 2A and 2B may be virtually any shape, but for a number of printer and display applications, the support member for supporting the mirror or reflective surface 42, which is preferably in the elongated ellipse form of FIG. 40; support member). The pivoting mirror is supported by a pair of torsional hinges 44a and 44b. Thus, it will be appreciated that if the mirror 42 can be kept vibrated around the axis 46 by the drive source, such a mirror can be used to repeatedly move the swept light beam across the photosensitive medium. .

It will be appreciated that other embodiments of a single axis arrangement may not require a support member or frame 40 as shown in FIGS. 2A and 2B. For example, as shown in both figures, the torsional hinges 44a and 44b are simply a pair of hinge anchor pads 48a and 48b, as shown by the dashed lines. Can be extended to). The functional surface, such as mirror 42, may be appropriately polished on its upper surface to provide a reflective surface or a mirror surface.

Single layer silicon mirrors are typically micro-electric mechanical systems (MEMS) type mirrors made from a single piece of single crystal silicon. Furthermore, because of the useful material properties of single crystal silicon, MEMS based mirrors have very sharp torsional resonances. The torsional resonance Q typically falls in the range of 100 to over 1000. This sharp resonance results in significant mechanical amplification in the device motion of the resonant frequency versus non-resonant frequency. Thus, it is typically advantageous to pivot the device around the scanning axis at the resonant frequency. This greatly reduces the power required to continuously vibrate the mirror.

FIG. 2C is a rear view of a multi-layered single axis torsion mirror device, somewhat similar to the monolithic extended ellipse shape illustrated in FIG. 2B. Components of the mirror apparatus of FIG. 2C that are the same as in the mirror of FIG. 2B have the same reference numbers. However, unlike the toroidal mirror of FIG. 2B, the torsional hinges do not extend between the anchors 48a and 48b and the reflective portion. Instead, the torsional hinges extend up to the attachment member 53 having a front and a back. The permanent magnet 50c is attached to the back side, and the mirror portion 55 is attached to the front side. Mirror portion 55 may be a flat monolayer of silicon, or preferably monolayer to provide a thin reflective portion 55a and a support rib as shown, as shown in FIG. 2C. It can be provided with a piece of silicon that includes a thick lip support portion 55b etched from the mirror portion 55 of.

If the mirror is to provide a beam sweep that vibrates along the scan axis, there are a number of possible drive mechanisms that can be used to provide vibration or pivoting motion. For example, FIG. 2A illustrates a magnet driven mirror in which a pair of permanent magnets 50a and 50b are mounted on tabs 52a and 52b, respectively. Permanent magnets 50a and 50b interact with a pair of coils (to be described later) disposed under the pivoting structure. The mechanical motion of the mirror at the scan axis or around the hinges 44a and 44b is typically required to be greater than 15 ° and may be as large as 30 °. Rather than being driven by a pair of magnets 50a and 50b shown in dashed lines, FIG. 2B illustrates the use of a single magnet 50c disposed in the center of the mirror 42. The drive mechanism for a single magnet 50c disposed in the center is discussed below. Resonant drive methods typically involve applying a small rotational motion directly to the torsionally hinged functional surface near the resonant frequency of the mirror. Alternatively, an inertial drive may provide motion to the entire structure at the resonant frequency, which then causes the mirror to resonate or oscillate around its torsional axis. In inertial resonant drive methods, very small motion of the entire silicon structure can cause very large rotational motion of the device. Suitable sources of inertial resonant drive include piezoelectric drives and electrostatic drive circuits.

Furthermore, by carefully controlling the dimensions (ie, width, length and thickness) of the hinges 44a and 44b, the mirror has a natural resonant frequency that is substantially equal to the desired operating pivoting speed or oscillation frequency of the mirror. It may also be prepared. Thus, by providing the mirror with a high resonant frequency substantially equal to a given pivoting speed or vibration frequency, the power load can be reduced.

Referring now to FIGS. 3A, 3B, 3C, and 3D, one prior art example of a laser printer that generates a beam sweep using a single axis vibration mirror is illustrated. As will be appreciated by those skilled in the art and illustrated in the following figures, prior art efforts typically involve using only one direction of the vibrating beam sweep due to non-parallel image lines generated by the return sweep. It has been limited. As shown in FIGS. 3A, 3B, 3C and 3D, the rotating polygon mirror is a single oscillation in both directions, as indicated by the double-headed bowed arrow 56. This alignment is virtually identical to that shown in Figures 1A, 1B and 1C, except that it has been replaced with a flat mirror of oscillating). As in the case for FIG. 1A, FIG. 3A illustrates the start of the beam sweep by a single axis mirror 54 at point 30. Similarly, arrows 32 and dashed lines 34 in FIG. 3B indicate the direction of the beam sweep as the mirror 54 rotates in the direction indicated by the arrow 56a so that the mirror 54 substantially completes its scan. To illustrate. Referring to the bottom view of the photosensitive drum 18 according to this prior art embodiment, the mirror 54 is mounted at a slight inclination such that the beam sweep is synchronized with the movement of the rotating drum 18, so that the distance the medium moves is swept. Is equal to the vertical distance the light beam travels. As in the case for the polygon mirror of FIG. 1B, the slightly tilted trajectory of the beam illustrated by dashed line 34 generates a horizontal image line 36 on the moving photosensitive medium 16 or drum 18.

Thus, so far, it will appear that a single torsional axis of the flat surface that vibrates the mirror 54 should operate like the rotating polygon mirror 10 discussed with reference to FIGS. 1A, 1B, and 1C at least. However, when the vibrating mirror begins to reverse pivot in the opposite direction as shown by the bowed arrow 56b, as in conventional scanning mirror printers, it is mounted at a slightly inclined angle. Since the vertical movement of the reflective beam resulting from the mirror and the movement of the moving photosensitive medium 16 or the rotating drum 18 are not subtracted but cumulative, during the return sweep, the beam indicated by the dotted line 34a in FIG. 3C is turned off. And do not print. Thus, if used for printing, the tilted trajectory 34a of the return beam combined with the movement of the rotating drum 18 is at a much larger angle than would simply be caused by the movement of the rotating photosensitive drum 18. It will tilt and result in the printed image line 36a. Of course, this means that when the beam sweep returns, the beam sweep is moved in the downward direction, as indicated by arrow 58, but not in the upward direction, while the movement of the photosensitive drum is indicated by the arrow 60. This is due to the fact that it is upward. Thus, as described above, the movement of the drum and the beam trajectory are cumulative. Therefore, it will be appreciated that for satisfactory printing by the resonant scanning mirror printer according to the prior art, during the return trajectory of the scan, the light beam and printing should typically be blocked and / or interrupted. Thus, the vibrating mirror 54 must complete its inversion scan and then start its forward scan, as indicated at 30, wherein the adjusted laser is turned on again and is indicated in FIG. 3D. As such, the second image line 36b is printed.

However, if the position of the scanning beam perpendicular to the sweeping motion can be controlled to compensate for the rotating or moving photosensitive medium, the laser beam can be adjusted on in both its forward and reverse scanning directions. Such vertical movement can be realized by using a dual axis scanning mirror or by providing a resonant beam sweep using a first single axis resonant mirror and providing controlled vertical motion using a second single axis mirror.

Referring now to FIGS. 4A and 4B, two embodiments of dual axis mirrors are illustrated. As can be readily seen, these mirrors are similar to the single axis mirrors of FIGS. 2A and 2B described above, respectively. However, instead of the primary or resonant hinges 44a and 44b positioned along the resonant axis 46 directly attached to the anchor pads 48a and 48b, the primary hinges 44a and 44b are formed of members of gimbals ( 62, the member 62 of gimbals is connected to the anchor pads 48a and 48b by a pair of second hinges 64a and 64b. Hinges 64a and 64b provide pivotal movement of mirror 42 along a second axis 66 that is substantially perpendicular to axis 46.

As shown, FIG. 4A is a perspective view of a single two-axis bidirectional mirror providing resonant motion about a first axis 46 and a resonant motion about a second axis 66 that is substantially perpendicular to the first axis. The mirror device can be used to provide back and forth pivoting beam sweeps, such as a projection display screen or resonant scanning across a moving photosensitive medium, as well as to maintain uniformly spaced parallel image lines generated by the resonant raster beam sweep. Can also be used to adjust the beam sweep in a direction perpendicular to the front and back pivoting of the reflective surface or mirror portion 42. As shown, the mirror is illustrated as suitable to be mounted on a support structure and may be formed from a substantially flat sheet of material (such as silicon) by techniques similar to those used in the semiconductor industry. As discussed above, the functional or movable components may be, for example, a pair of support members or anchors 48a and 48b, intermediate gimbals portion 62 and internal mirror or reflective surface portion 42. It includes.

4B is another embodiment of a dual axis mirror having an elongated oval mirror portion 42a and a drive magnet 50c disposed centrally. The remaining elements of the device shown in FIG. 4B operate or function in the same manner as the equivalent elements of FIG. 4A, so the two figures use common reference numerals.

5 is a schematic diagram illustrating how resonant sweep and / or vertical motion is controlled by electromagnetic coils 68a and 68b. To provide resonant pivoting motion, the coils 68a and 68b are driven by an alternating voltage source 70 having a frequency substantially the same as the resonant frequency of the mirror. Permanent magnet sets 50a and 50b can be bonded to the mirror 42 (or gimbals portion 62), so that they cooperate with the electromagnetic coils 68a and 68b. Thus, as the two coils 68a and 68b switch back and forth between the N and S poles, the permanent magnets 50a and 50b are alternately repelled and attracted to create a resonance vibration. If coil alignment and magnet pairs must provide vertical motion, much slower frequencies are used.

Referring now to FIG. 6, there is a simplified view of the permanent mirror alignment with the pivoting mirror 42 or 42a and other coils that significantly reduce the moment of inertia of the device. As shown, two permanent magnets have been removed and a single magnet 72 is mounted in the center of the pivoting mirror (as shown in FIG. 4B). According to the embodiment shown in FIG. 6, the magnet 72 is not a axial charge, but rather a diametral charge perpendicular to the axis of rotation, as exemplified by the double head arrow 74. Have Of course, it will also be necessary to reposition the drive coil 76 of the electromagnetic device 77 such that the drive coil 76 of the electromagnetic device 77 is substantially below the magnet 72. Thus, as the electromagnetic device 77 switches back and forth between the north and south poles, the diameter-filled " N " and " S " poles of the permanent magnets 72 alternately repulse or are attracted to the shaft 46 To generate pivotal vibrations.

7 shows a second drive alignment suitable for use with a single magnet disposed in the center. As shown, instead of the diameter filled magnet of FIG. 6, an axially filled magnet 78 is used. Further, the coil 76 shown in FIG. 6 includes a coil 82 and strut members 84a and 84b extending from the coil 82 to the tips 86a and 86b on each side of the magnet 78. Is replaced by an electromagnetic alignment 80. Thus, an alternating current applied to the coil 82 generates a magnetic field whose polarity continues to change at the tips 86a and 86b of the posts 84a and 84b. This change in polarity creates alternating push-pull forces in the magnet 78.

8 illustrates a perspective view of a scanning mirror used to generate an image on medium 88. Mirror device 90, such as a single axis mirror of the type shown in FIGS. 2A and 2B, has a reflective surface 42 of mirror device 90 receiving light beam 14a from source 12, and limits. At 92 and 94 limits, we pivot around its single axis 46 to provide a right and left to right resonant sweep at the right of the beam 14b. This left to right and right to left beam sweep provides constant spaced lines 96 and 98 as the medium 88 moves in the direction indicated by the arrow 100.

Although various forms of mirror may be used in the practice of the present invention, the demand for higher and higher operating speeds will require higher and higher oscillation speed of the mirror around the primary or scan axis 46. However, in addition to high speed pivoting of the scanning mirrors, it is also important that the mirror does not deform when the mirror is pivoting. More specifically, it is important that the mirror does not deform when the mirror sweeps the laser beam across the photosensitive medium during the scan period. Thus, for high speed resonant mirrors, magnetic drives using a centrally placed single mirror will have less moment at the edges of the mirror and thus have a reduced moment.

More specifically, at high pivoting speeds, the tips of the preferred elongated elliptical mirror shown in FIG. 2B are subject to significant inertia as they move at very high speeds. Thus, when permanent magnets 50a and 50b are attached to the tips of an elongated elliptical mirror, as shown in FIG. 2B, the mirror will generally tend to bend excessively at torsional hinges and tips. Such excessive bending, of course, means that during some parts of the oscillation period, the mirror surface is not flat due to bending or bending. This change in mirror flatness at high frequencies is not readily acceptable in many displays and printers. However, the use of a centrally placed mirror 50c not only prevents excess weight at the mirror tips, but also provides stiffness in the center of the mirror.

The operation of the dual axis mirror, as shown in FIGS. 4A and 4B for providing a pivoting beam sweep in connection with the projection display screen 102, may be better understood by referring to FIG. 9. As shown, the laser light source 12 provides a coherent light beam 14a to the reflective surface 42 of the dual axis mirror apparatus 104, and the reflective surface 42 of the dual axis mirror apparatus 104. Reflects light beam 14b onto display screen 102. Reflective surface 42 oscillates back and forth at resonant frequencies around torsional hinges 44a and 44b along axis 46 such that beam 14b is indicated by an arrow 112 parallel to the light beam labeled 114. As shown, sweeps across display screen 102 from location or point 108 to endpoint 110 along image line 106. Vibration mirror 42 then generates an image line 118 between points 110 and 120 by changing direction and starting the return sweep, as indicated by arrow 116. After the pass point 120, the beam again begins to reverse direction. While the beam sweeps back and forth, the beam can also be moved vertically at much slower speed, as indicated by arrow 122. This sweeping and vertical movement is repeated until the last image line 124 of the display frame ending at point 126 is generated on the display screen 102. Then, to start a new display frame, it is quickly moved vertically from the end point 126 to the start point 108, as indicated by the dashed line 128.

Referring to FIG. 10, a perspective view of another embodiment of the present invention in which the vertical movement of the beam is realized by the second mirror 132 is illustrated. Each of the two mirrors 130 and 132 pivots around a single axis, like single axis mirrors of the type shown in FIGS. 2A and 2B. The scanning and vertical operation of the two single axis mirrors is in fact identical in other respects.

Thus, according to another embodiment of the present invention, FIG. 10 provides a first embodiment that provides a resonant sweeping beam such as that used with a similar second single-axis torsion mirror to be used in a projection display (or laser printer). Illustrate a single axis torsionally hinged mirror. As shown in this embodiment, it includes a pair of support members or anchors 48a and 48b that support the mirror or reflective surface 42 by a pair of torsional hinges 44a and 44b. The first mirror device 130 is illustrated. Thus, it will be appreciated that if the mirror portion 42 can be pivoted back and forth by the drive source, the mirror can be used to generate a vibrating light beam across the photosensitive display. As discussed, a particular useful method of pivoting the mirror back and forth is to generate a resonant vibration of the mirror around the torsional hinges 44a and 44b. However, as also discussed, there is also a need for a method of moving the light beam in a direction perpendicular to vibration. Thus, as illustrated, a second single axis mirror device 132 is used, so that the second single axis mirror device 132 pivots about its axis 46, thereby allowing the vertical movement of the light beam to be shifted. to provide.

As discussed above, the optical system of the embodiment of FIG. 10 uses a single axis mirror arrangement 130 to provide right to left and left to right pivoting, represented by dotted lines. However, up and down control of the beam trajectory results in a sweep motion in which the reflective surface or mirror blocks the light beam 14 emitted from the light source 12 and then pivots the blocked light 14a back and forth. It is realized by arranging the second single axis mirror device 132 to reflect to the providing mirror device 130. The distance 133 indicated on the mirror surface 42 of the resonant mirror 130 is during the left to right and right to left beam sweep to provide the data lines 106, 118 and 124 to the projection display screen. Illustrates how the mirror 132 rotates about the axis 46 to move the light beam 14a up and down on the reflective surface 42 of the mirror device 130.

As mentioned above, in an attempt to increase printing speed, printer manufacturers using rotating polygon mirrors sometimes have a large number of spaced at equal intervals to increase the number of data lines generated on the photosensitive medium during a single sweep. Use parallel laser beams. Referring now to FIG. 11, a laser beam source 134 is illustrated with four beam outputs 136, 138, 140, and 142 reflected from the rotating polygon mirror 144 onto the rotating photosensitive drum 146. . The process is important, except that it is important to ensure that the data lines generated by the first facet of the polygonal mirror are properly maintained at regular intervals with respect to the lines generated by the second and subsequent facets. It is virtually identical to the case.

More specifically, since multiple laser beams, such as beams 136, 138, 140 and 142, are spaced at a fixed equidistant distance, four data lines 148, 150, 152 generated on the photosensitive medium by the first facet. And 154 will clearly be equally spaced and parallel to each other. Furthermore, the next four data lines 148, 150, 152 and 154 generated by the next or subsequent facet will also be equidistant and parallel. However, it is also important that the first data line 148 generated by the second facet be equidistant and parallel to the last data line 154 generated by the first or preceding facet. To realize this, the movable medium or the rotating drum 146 crosses the movable medium during a complete single sweep of four beams, with the spacing between the laser beams ("S") x the number of laser beams ("N") and You must move the same distance ("D"). In other words, D = (S) (N). Thus, it can be seen that the only requirement in using multiple beams for the polygon mirror is that the rotational speeds of the polygon mirror and the moving photosensitive medium must be carefully synchronized.

Using multiple laser beams in a bidirectional resonant scanning mirror is much more difficult, and for most applications, the physical alignment will be substantially the same as polygon mirrors and multi laser beams, but will be limited to even laser beams. Referring now to FIG. 12, a perspective view similar to that of FIG. 11 is illustrated except that a bidirectional resonant scanning mirror 156 pivoting around axis 158 is used instead of the polygon mirror. The advantage arises because the top traces of the reverse or return sweep will intersect the bottom or lower traces generated by the preceding forward sweep. Thus, intersecting traces must carry the same data. As will be seen in the following, this double printing of each line allows parallel print lines without requiring a double axis mirror and also provides greater intensity resolution per spot.

More specifically and referring to FIG. 13A, traces of two parallel laser beams 166 and 168 over four complete sweep periods are illustrated. As shown, forward traces 166a and 168a are generated as laser beams 166 and 168 and are accompanied by inverted traces 166b and 168b that move from right to left and move from left to right. The laser beams will only be adjusted while the beams pass through the printing area delimited by the left edge 170 and the right edge 172. Since the oscillating mirror speed is decelerated to zero at the end of each sweep before inverting the direction, by the sweep regions 174 and 176 on each side of the printing area, the four beams reach an acceptable speed before they are adjusted with data. can do. However, as shown in FIG. 13A, the forward trace 166a at the top provided by the laser 166 intersects the inversion trace 168b of the laser 168 from the preceding period at the intersection point 178. do. Similarly, inverted trace 166b of laser 166 intersects forward trace 168a of equal period laser 168 at intersection 180. This cycle is repeated over and over. Thus, it should be appreciated that if the forward trace of laser 166 is adjusted in the same order but reversed from the laser 168 inversion period from the preceding period, the two intersecting traces of the data lines should be identical. Likewise, if the inverted traces of laser 166 are adjusted in the same order but in the same order as the forward traces of laser 168, these two intersecting traces or data lines will also be the same. Thus, in a two laser beam system, each data line is printed twice, once in each direction. However, two data lines or traces are printed during each sweep period. More specifically, each data line is printed once by both laser beams by traces crossing each other. This double printing provides an inexpensive technique for increasing printing quality or speed.

As discussed in connection with rotating polygon mirrors and multi-laser beam sources, in order to realize the highest quality printing, the relative movement between the multiple sweeping beams and the photosensitive medium receiving the laser beams must be synchronized. Thus, the relative total distance traveled between the swept laser beam and the photosensitive medium ("D") during the complete back and forth sweeping period is equal to the spacing ("S") × number of multiple laser beams ("N") between parallel laser beams. You should know that they are the same. In other words, D = (S) (N) or, in the case of a two laser beam system, D = 2S.

If two laser beams can be used to increase printing quality or speed, it will be appreciated that the use of a laser source of four laser beams will allow for a greater speed increase or an increase in both quality and speed.

Thus, referring now to FIG. 13B, traces generated by four parallel laser beams 182, 184, 186 and 188 spaced at equal intervals reflected onto a photosensitive medium moving by a vibrating mirror are illustrated. This trace diagram is similar to the trace diagram of FIG. 13A showing two laser beams. However, as can be seen within printing limits 190 and 192, not all four laser beams intersect each other at a given point on the medium, but laser beam 182 moves in either the forward or reverse trace direction. Depending on where it is, it only intersects with the laser beam 186. Similarly, within the printing limits 190 and 192 only the laser beams 184 and 188 cross each other. Thus, four different data lines 194, 196, 198 and 200 can be printed twice during each complete sweep period. More specifically, the first 194, second 196, third 198 and fourth 200 data lines are respectively the first 182 and the second 184 in the first or forward sweep directions, respectively. ), Generated by the third 186 and fourth 188 light beams, while the same first 194, second 196, third 198 and fourth 200 data lines, respectively, It is generated with third 186, fourth 188, first 182 and second 184 laser beams in the reverse or opposite direction.

With reference to FIG. 14, a graph showing the line density across the printing area for individual scans as well as the line density of the double traces for left to right and right to left scans across the printing areas of the media. As shown, the top curve 202 represents the line density of the central region produced by the combination of both forward sweep and return sweep. Curve 204 is the line density at the edges of the printing area, produced by both forward and reverse sweeps. Curve 206 represents the line density at the printing area edge at the left to right scan of a single trace, while curve 210 represents the line density at the printing area edge at the left to right scan of a single trace. . Curve 208 represents the line density at the center of the line or printing area of both left to right and right to left scans. As expected, traces of the line density of the two beams in the center regions are identical and overlap each other, provided that the outputs of the two lasers are substantially the same. Thus, as can be seen by writing or generating each line twice, the density variation across the entire write line is minimal and the lines appear substantially parallel.

Although the invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made without departing from the scope of the invention as defined by the appended claims.

Furthermore, the scope of the present application is not limited to the particular embodiments of the process, machine, product, composition of matter, means, methods and steps described in the specification. Those skilled in the art, from the teachings of the present invention, processes, machines, products, issues, present or later developed, which perform substantially the same functions or realize substantially the same results as the corresponding embodiments described herein. It will be readily appreciated that configurations, means, methods, or steps of may be used in accordance with the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, products, configurations of matter, means, methods, or steps.

Claims (17)

A method of generating data lines on a photosensitive medium, Providing a photosensitive medium; Oscillating the reflective surface about a first pivot axis; Directing a plurality of coordinated parallel light beams onto the vibrating reflective surface; Reflecting the plurality of coordinated parallel light beams from the vibrating reflective surface to sweep the light beams back and forth across the photosensitive medium in forward and reverse directions; Providing a relative orthogonal movement between the forward and reverse directions of the swept light beams and the photosensitive medium; And Generating a plurality of selected data lines on the photosensitive medium as the plurality of adjusted parallel light beams sweeps across the photosensitive medium. How to include. The method of claim 1, The generating step, Generating the plurality of selected data lines as the plurality of light beams sweeps across the photosensitive medium in the forward direction; And Generating the plurality of selected data lines as the plurality of light beams sweeps across the photosensitive medium in the reverse direction, wherein each of the plurality of light beams is one of the plurality of selected data lines, respectively. Providing a data line in the reverse direction different from that provided in the forward direction How to include. The method of claim 2, The multiple light beams include "N" light beams that are equally spaced by a distance "S", and during one complete back and forth cycle, between the directions of the light beams and the photosensitive medium. Wherein said relative vertical movement is equal to distance (S) × (N). The method of claim 1, The multiple light beams are two light beams, The generating step, As a first light beam of the two light beams and a second light beam of the two light beams move in the forward direction, generate a first data line with the first light beam and generate a second data line with the second light beam. Making a step; And Generating the second data line with the first light beam and generating the first data line with the second light beam as the first and second light beams move in the reverse direction. How to include. The method of claim 4, wherein Wherein the two light beams are spaced apart by a distance “S” and the relative vertical movement between the two swept light beams and the photosensitive medium is equal to 2S. The method of claim 1, The plurality of light beams comprises a first light beam, a second light beam, a third light beam and a fourth light beam, The generating step, As the light beams sweep across the photosensitive medium in the forward direction, generating first, second, third and fourth selected data lines with the first, second, third and fourth light beams, respectively. step; And As the light beams sweep across the photosensitive medium in the reverse direction, generating the first, second, third and fourth selected data lines with the third, fourth, first and second light beams, respectively. Letting step How to include. The method of claim 6, Wherein the four light beams are equidistantly spaced by a distance “S” and the relative vertical movement between the four swept light beams and the photosensitive medium is equal to 4S. The method of claim 1, Providing the relative movement comprises moving the photosensitive medium in a direction perpendicular to the plurality of sweeping beams. The method of claim 1, Providing the relative movement includes mounting the vibrating reflective surface to a second pivot axis perpendicular to the first pivot axis, and pivoting the vibrating reflective surface around the second pivot axis. How to include. The method of claim 1, Providing the relative movement comprises blocking the plurality of coordinated parallel light beams at another reflective surface having a pivot axis for moving the plurality of light beams perpendicular to the swept light beams. An apparatus for generating data lines on a photosensitive medium, the apparatus comprising: A source of multiple parallel light beams spaced at equal intervals; A reflective surface that receives and reflects the plurality of equidistant parallel light beams, the reflective surface being pivotally mounted about a selected axis to sweep the reflected multiple parallel light beams back and forth; A photosensitive medium arranged to block the parallel light beams from the reflective surface, the light beams sweeping the photosensitive medium in a forward and reverse direction; And Control circuitry for selectively adjusting each of the plurality of equidistant light beams to generate the data lines as the light beams sweep across the photosensitive medium Device comprising a. The method of claim 11, The source provides two parallel light beams spaced apart, The reflecting surface and the control circuit adjust the first light beam of the two light beams to generate a first data line and adjust the second light beam of the two light beams as the light beams sweep in the forward direction. Generate two data lines and adjust the first light beam to generate the second data line and adjust the second light beam to generate the first data line as the light beams sweep in the reverse direction. Device. The method of claim 11, The source provides four parallel light beams spaced at equal intervals, The reflective surface and the control circuit adjust a first data line by adjusting a first light beam, a second light beam, a third light beam and a fourth light beam of the four parallel light beams as the four parallel light beams move in the forward direction. A second data line, a third data line and a fourth data line on the photosensitive medium, respectively, and as the four parallel light beams move in the reverse direction, the first, second, third and fourth And adjust the light beams to generate the third, fourth, first and second data lines on the photosensitive medium, respectively. The method of claim 11, And the photosensitive medium moves perpendicularly to the swept adjusted equally spaced parallel light beams at a selected speed. The method of claim 14, And the photosensitive medium is a rotating photosensitive drum. The method of claim 11, And the reflective surface is pivotally mounted to rotate about a second pivot axis perpendicular to the first pivot axis to move the multiple light beams in a direction perpendicular to the sweep across the photosensitive medium. The method of claim 11, And a second reflective surface mounted pivotally to move the plurality of parallel light beams perpendicularly to the sweeping movement.

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