JP2006039190A - Optical recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain high recording quality without fluctuations in the scanning line gaps. <P>SOLUTION: A multibeam scanning optical recording apparatus has a light source for generating a plurality of beams which emits laser beams; a photoreceptor drum on which a plurality of focused spot lines are formed by laser beam scanning; and an optical system which transmits the laser beams which form the plurality of imaging focused spot lines. The multibeam scanning optical recording apparatus is characterized by that a reflection element array, including a micromirror array which is driven in accordance with the respective laser beams, is arranged in the optical system, and the scanning line gaps between the plurality of focused spot lines are adjusted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to an optical recording apparatus such as a laser beam printer that performs optical recording by scanning and modulating a plurality of laser beams.

  In recent years, in laser scanning image forming apparatuses such as laser printers and laser facsimiles, a plurality of scanning lines are simultaneously formed on a surface to be scanned such as a photosensitive member by a plurality of light beams as means for realizing high speed and high resolution. A multi-beam scanning optical system to be formed is essential.

  As means for forming a plurality of scanning lines by multi-beams, a plurality of semiconductor lasers are used as a light source, a beam combining method for combining light beams from the respective semiconductor lasers by a polarization beam splitter, etc., and a plurality of light emitting points as a light source A system using a semiconductor laser array, an optical fiber having a light source formed from an optical fiber array in which light emitted from independent semiconductor lasers is incident on an optical fiber and the light emitting side tips of the optical fibers are arranged close to each other and arranged in a line An array method or the like is well known. For example, Patent Literature 1, Patent Literature 2, Patent Literature 3, Patent Literature 4, and Patent Literature 5 can be cited.

  Among these, the semiconductor laser array can realize a simple optical system configuration, but it is difficult to obtain the element itself, and the tendency becomes remarkable particularly when the number of beams increases. In addition, it is difficult to obtain a semiconductor laser array having a short oscillation wavelength because of technical difficulties, and even if it can be obtained, it is very expensive.

  On the other hand, the beam synthesis method has an advantage that a general-purpose semiconductor laser can be used. However, the adjustment accuracy for setting a predetermined scanning line interval on the photosensitive member is strict, and the semiconductor laser is caused by temperature fluctuation or vibration. The relative position of the beam on the photosensitive member may fluctuate greatly even with minute fluctuations between them, so that it is difficult to keep the scanning line interval stable.

  On the other hand, the optical fiber array method can use general-purpose semiconductor lasers in the market, and the strict accuracy of the adjustment mechanism used in the beam synthesis method is not required by arraying the tip of the optical fiber. There are advantages. However, in this method, since the alignment accuracy of the beams emitted from the individual optical fibers forming the optical fiber array directly corresponds to the spacing error between the scanning lines formed on the photosensitive member, the optical fiber array is manufactured. Requires strict accuracy. For this reason, when an optical fiber array with low accuracy is used, there is a problem in that the image quality is adversely affected.

JP 2003-131155 A JP-A-10-177145 JP-A-11-84283 JP 2001-242403 A JP 2003-35876 A

  In the above-described multi-beam scanning optical recording apparatus, if there is an error in the individual beam generation positions of the multiple beam generation light sources, an error also occurs in the interval between the scanning lines formed by each beam that performs batch scanning. It is a point that adversely affects.

  An object of the present invention is to address the above-described problems, and to obtain a multi-beam scanning type optical recording apparatus that can provide good recording image quality even if there is an error in the individual beam generation positions of a plurality of beam generation light sources. .

  According to the present invention, in a multi-beam scanning type optical recording apparatus, a plurality of connections formed on a photosensitive drum are provided through a reflection element array including a micromirror array that can be driven corresponding to each laser beam. It is characterized in that the scanning line interval between image spot rows can be adjusted.

  More specifically, the micromirror array is provided at a position satisfying the following expression.

Where L is the distance from the multiple beam generating light source to the position where the micromirror array is arranged δFA is the size of each light emitting portion of the multiple beam generating light source and 1 / (e ² ) of the center light intensity
Level half width λ: Light source wavelength dFA: Interval between light emitting portions of a plurality of beam generating light sources.

  According to the present invention, since the error of the scanning line interval can be finely adjusted by the reflective element array, it is possible to provide a good recording image quality.

  The present invention provides a multi-beam scanning type optical recording apparatus that simultaneously scans a plurality of rows of laser beams at once, and uses a reflective element array to greatly adjust the variation in scanning line interval variation. Realized easily without changing to.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the outline of the optical system of the multi-beam scanning optical recording apparatus will be described with reference to FIG.

  Each of the semiconductor laser module units 1 to 5 is constituted by a plurality of independent semiconductor lasers and a coupling optical system for making light emitted from the semiconductor lasers incident on optical fibers 6 to 10 corresponding to the individual semiconductor lasers. Is done.

  Single mode optical fibers are used for the optical fibers 6 to 10. The light emission side tips of the optical fibers 6 to 10 form an optical fiber array 11 arranged close to each other and arranged in a row, and light emitted from the optical fiber array 11 is used as a light source for generating a plurality of beams.

  Individual semiconductor lasers emit laser beams 13 to 17 according to the image data signal 12 from the controller, thereby emitting individually modulated beams 18 from the tips of the optical fiber array 11. In FIG. 1, for convenience, five beams are used.

  The light emitted from the optical fiber array 11 is collimated by the lens 19 through the mirror 26 and the micromirror array 27 as a reflection element array, and then enters the lens 20 and is formed by the lens 20 and the lens 21. It is converted into parallel light with an expanded beam width by an expander.

  An enlarged view from the optical fiber array 11 to the micromirror array 27 is shown in FIG.

  Thereafter, the light emitted from the lens 21 passes through a cylinder lens 22 having lens power only in the sub-scanning direction, and is then imaged as a spot row on the photosensitive drum 25 by the rotary polygon mirror 23 and the scanning lens 24, and individually. Optical recording is performed on the photosensitive drum 25 by scanning the modulated spot.

  At this time, the plurality of imaging spots 31 to 35 imaged on the photosensitive drum 25 have an oblique angle so that the scanning lines formed by the respective imaging spots are in close contact with each other. This oblique angle is set by rotating and adjusting the optical fiber array 11 around the optical axis. The cylinder lens 22 disposed in front of the rotary polygon mirror 23 is for eliminating the deviation of the scanning line in the sub-scanning direction due to the swinging of the rotary polygon mirror 23 during rotation. The image is narrowed down in the sub-scanning direction on the surface.

  2 and 3 are diagrams showing details of the component arrangement position of the optical system shown in FIG. 1, and FIG. 2 shows the optical system in the rotating plane of the rotary polygon mirror 23, that is, the photosensitive drum 25 in the main scanning direction. It is an optical system. FIG. 3 shows an optical system viewed from the vertical direction, that is, an optical system in the sub-scanning direction. In FIGS. 2 and 3, the number of beams is three in order to avoid complications.

  2 and 3, when the focal lengths of the lens 19, the lens 20, the lens 21, and the lens 22 are fcol, fL1, fL2, and fcyl, respectively, the distance between the optical fiber array 11 and the lens 19 is fcol, and the lens 19 and the lens. The distance 20 is fcol + fL1, the distance between the lens 20 and the lens 21 is (fL1 + fL2), and the distance between the lens 21 and the rotary polygon mirror 23 is approximately fL2.

  By arranging in this way, in FIG. 1, the principal rays of the respective laser beams emitted in parallel from the optical fiber array 11 are made parallel again after being emitted from the lens 20, and the lens 21 is irradiated. Thereafter, the principal rays of the beams emitted from the lens 21 are approximately matched on the rotary polygon mirror 23. By doing so, it is not necessary to increase the size of the rotary polygon mirror 23 even when a plurality of beams are used, and a conventional one can be used.

  Next, each laser beam emitted from the optical fiber array 11 will be described with reference to FIGS.

  Assuming that the diameter of the beam emitted from each optical fiber of the optical fiber array 11 is δFA [μm] and the arrangement interval of each beam is dFA [mm], the lens 19 has a condition that the beams emitted from the optical fiber array 11 cannot be removed. Below, the beam diameter DCOL after emission from the lens 19, the imaging spot diameter δL1 between the lens 20 and the lens 21, the arrangement interval dL1 of the imaging spots, and the beam diameter DL2 after emission from the lens 21 are expressed by the following equations. Is done.

DCOL = 4 · λ · fcol / (π · δFA) [mm] (Formula 1)
δL1 = δFA · (fL1 / fcol) [mm] (Equation 2)
dL1 = dFA · (fL1 / fcol) [mm] (Equation 3)
DL2 = 4 · λ · fcol · fL2 / (fL1 · π · δFA) [mm] (Formula 4)
Here, λ is the wavelength of light.

  On the other hand, in the optical system in the sub-scanning direction of FIG. 3, until the lens 21 emits parallel light having a beam diameter DL2 = 4 · λ · fcol · fL2 / (fL1 · π · δFA) [mm]. Although it is the same as the optical system of FIG. 2, the light emitted from the lens 21 is narrowed down on the rotary polygon mirror 23 by the cylinder lens 22.

If the size (vertical diameter) in the sub-scanning direction of the spot focused on the rotary polygon mirror 23 is δPOL [μm], δPOL is expressed by the following equation.
δPOL = {(fL1 · fcyl) / (fcol · fL2)} δFA [μm] (Expression 5)
Further, when the interval in the sub-scanning direction of the spots narrowed down on the rotary polygon mirror 23 is PPOL, the following relationship is established.

PPOL∝ {(fL1 · fcyl) / (fcol · fL2)} (Expression 6)
Therefore, a light spot having a horizontal width DL2 [mm], a vertical width δPOL [μm], and an interval PPOL is formed on the reflecting surface of the rotary polygon mirror 23 as shown in FIG.

  The light reflected by the rotary polygon mirror 23 forms an image on the photosensitive drum 25 by the scanning lens 24. At this time, if the focal length of the scanning lens 24 is fFΘ, the imaging spot diameter on the photosensitive drum is expressed by the following equation.

ωx = {(fL1 · fFΘ) / (fcol · fL2)} δFA [μm] (Expression 7)
ωy = mδPOL = m {(fL1 · fcyl) / (fcol · fL2)} δFA [μm] (Equation 8)
Here, ωx is the imaging spot diameter in the scanning direction, ωy is the imaging spot diameter in the sub-scanning direction, and m is the magnification of the scanning lens 24 in the sub-scanning direction.

  That is, the overall magnification of this optical system is expressed by the following equation, where mmain is the main scanning direction and msub is the sub-scanning direction.

mmain = ωx / δ = {(fL1 · fFΘ) / (fcol · fL2)} (Equation 9)
msub = ωy / δ = m {(fL1 · fcyl) / (fcol · fL2)} (Equation 10)
As will be described later, since the angle of the imaging spot row arranged on the photosensitive drum 25 with respect to the scanning line is small, dDRUM is approximated by the following equation using (Equation 9), where each imaging spot interval is dDRUM. Is done.

dDRUM ≒ mmain ・ dFA
= DFA · {(fL1 · fFΘ) / (fcol · fL2)} [mm] (Equation 11)
If the inclination of the multi-beam imaging spot with respect to the optical scanning direction is ψ, the scanning line interval pitch is given by the following equation.

pitch = dDRUM · sinΨ
= DFA · {(fL1 · fFΘ) / (fcol · fL2)} · sinψ [mm] (Equation 12)
Consider an optical recording apparatus having a resolution of 600 [dot / inch] by substituting specific numerical values for each variable of the optical system described above.

The light source wavelength is λ = 0.635 [μm], the emission spot diameter of the optical fiber array 11 is δFA = 5 [μm], the beam interval is dFA = 0.25 [mm], and the focal length of the lens 19 is fcol = 20 [ mm], the focal length of the lens 20 is fL1 = 200 [mm], the focal length of the lens 21 is fL2 = 400 [mm], the focal length of the lens 22 is fcyl = 200 [mm], and the focal length of the lens 24 is fFΘ = If 400 [mm] and the magnification of the lens 24 is m = 2 [times], DCOL, δL1, dL1, DL2, and dDRUM are
DCOL = 3.234 [mm] (Equation 13)
δL1 = 50 [μm] (Equation 14)
dL1 = 2.5 [mm] (Equation 15)
DL2 = 6.468 [mm] (Expression 16)
dDRUM = 2.5 [mm] (Expression 17)
It becomes.

Also, assuming that the overall magnification of the optical system in the main scanning direction and the sub scanning direction is mmain and msub, respectively, and the imaging spot diameters in the main scanning direction and the sub scanning direction are ωx and ωy, respectively.
mmain = 10 [times] …… (18)
msub = 10 [times] (19)
ωx = 50 [μm] ………… (20)
ωy = 50 [μm] ………… (21)
It becomes.

Further, if the angle ψ with respect to the scanning line of the imaging spot row on the photosensitive drum 25 is set to ψ = 0.97 [deg], from (Equation 12),
pitch = 0.25 · {(200 · 400) / (20 · 400)} · sin 0.97
= 42.3 [μm] (Equation 22)
Thus, the scanning line interval has a resolution of 600 [dot / inch].

  In the above optical system, when there is an arrangement error in the optical fibers forming the optical fiber array 11, there arises a problem that the scanning line interval of the photosensitive drum 25 does not become a desired value. For example, when there is an arrangement error in one of the optical fibers 36 to 40 forming the optical fiber array 11 as in the emission end face of the optical fiber array 11 shown in FIG. Further, as shown in FIG. 6, the deviation from the beam emitting portion arrangement position of other optical fibers causes a variation error in the interval between scanning lines for collectively scanning on the photosensitive drum 25, which causes the image quality to deteriorate.

  Therefore, in order to solve this problem, the optical recording apparatus of the present invention is a micromirror in which the scanning line interval error caused by the optical fiber array error generated in the optical fiber array 11 is arranged in the optical path shown in FIG. The array 27 is driven corresponding to each beam, and the scanning line interval error is corrected by changing the reflection angle. As a result, it is possible to obtain a high-quality print image quality with no variation in the scanning line interval.

  Micromirror arrays whose reflection angles can be varied according to the respective beams are described in “Optical Micromachine (2002, Ohm)”, “Micromachine Technology and Applications (2002, Technical Information Center)”, etc. As described above, in recent years, it can be manufactured by etching a silicon substrate and using a MEMS (Micro Electro Mechanical Systems) technique.

Here, as shown in FIG. 8, when the beam emitted from the optical fiber array 11 is a Gaussian beam having a beam waist 2δFA (full width of 1 / (e ² ) of the center light intensity) at the emission end, The beam size 2ω (the full width of 1 / (e ² ) of the central light intensity) at the position of the distance z is expressed by the following equation.

2ω (z) = 2δFA√ [1 + {(λ · z) / (π · δFA ² )} ² ] (Formula A)
Where λ is the light source wavelength.

  From this, the following equation is obtained when an area in which the size of twice the Gaussian beam does not overlap with the adjacent beam is obtained using equation (A).

However, L is the distance from the multiple beam generating light source to the micromirror array arrangement position.
As a result, the micromirror array 27 can be deflected independently from each other without interfering with adjacent beams by being arranged at a position satisfying the above-described (formula B), and the arrangement of the optical fibers generated in the optical fiber array 11 It is possible to correct the deviation of the scanning line interval on the photosensitive drum 25 caused by the error.

  At this time, the beam interval detector 41 is disposed at a position equivalent to the beam scanning surface of the photosensitive drum 25 of the optical system shown in FIG. 1, and the scanning line interval error detected thereby is the micromirror. By feeding back to the array control circuit 42 and moving each micromirror array, it is possible to automatically eliminate the scanning line interval error.

  As described above, in the above embodiment, the number of beams used in the optical recording apparatus is 5. However, the number of beams is not limited to this and may be 5 or more.

  In addition, as a multi-beam optical recording method, a plurality of semiconductor lasers are used, a beam combining method in which light beams from the respective semiconductor lasers are combined by a polarization beam splitter, etc., and a method in which a semiconductor laser array having a plurality of light emitting points is used as a light source. The present invention is also applicable.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which concerns on the Example of this invention and shows the optical system outline of an optical recording device. FIG. 9 is an explanatory diagram illustrating the positional relationship of components in the main scanning direction with respect to the optical system of the optical recording apparatus according to an embodiment of the present invention. FIG. 5 is an explanatory diagram illustrating a positional relationship of components in the sub-scanning direction with respect to the optical system of the optical recording apparatus according to an embodiment of the present invention. FIG. 7 is an explanatory diagram illustrating a beam arrangement relationship in a rotary polygon mirror portion of an optical system of an optical recording apparatus according to an embodiment of the present invention. It is an explanatory view of the fiber arrangement error of the optical fiber array according to the embodiment of the present invention. It relates to the embodiment of the present invention and is an explanatory diagram of a scanning line interval error. FIG. 4 is an enlarged view from an optical fiber array to a micromirror array according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser module, 2 ... Semiconductor laser module, 3 ... Semiconductor laser module, 4 ... Semiconductor laser module, 5 ... Semiconductor laser module, 6 ... Optical fiber, 7 ... Optical fiber, 8 ... Optical fiber, 9 ... Optical fiber, DESCRIPTION OF SYMBOLS 10 ... Optical fiber, 11 ... Optical fiber array, 12 ... Image data signal, 13 ... Semiconductor laser driver, 14 ... Semiconductor laser driver, 15 ... Semiconductor laser driver, 16 ... Semiconductor laser driver, 17 ... Semiconductor laser driver, 18 ... Light Fiber array outgoing beam, 19 ... lens, 20 ... lens, 21 ... lens, 22 ... cylinder lens, 23 ... rotating polygon mirror, 24 ... scanning lens, 25 ... photosensitive drum, 26 ... mirror, 27 ... micromirror array, 31 ... Imaging spot 32 ... imaging spot 33 ... imaging spot 34 Imaging spot, 35 ... imaging spot, 36 ... light exit end of optical fiber, 37 ... light exit end of optical fiber, 38 ... light exit end of optical fiber, 39 ... light exit end of optical fiber, 40 ... optical fiber , 41... A beam interval detector, 42... Micromirror array control circuit.

Claims (5)

A plurality of beam generating light sources for emitting laser light, a photosensitive drum formed so that a plurality of imaging spot rows imaged by scanning of the laser light are arranged, and the laser light forming the plurality of imaging spot rows A multi-beam scanning type optical recording apparatus having an optical system for transmitting
A reflection element array including a micromirror array that can be driven corresponding to each of the laser beams is arranged in the optical system so that a scanning line interval between the plurality of imaging spot rows can be adjusted. An optical recording apparatus. A plurality of beam generating light sources that emit laser light, a photosensitive drum that is formed so that a plurality of imaging spot rows that are imaged by scanning of the laser light are arranged on an outer peripheral surface, and the plurality of imaging spot rows are formed An optical system for transmitting the laser light,
The optical system includes an optical fiber connected to the plurality of beam generation light sources, and a reflecting mirror, a lens, and a rotating polygonal mirror arranged next to the light emitting end side of the optical fiber,
A reflective element array including a micromirror array that can be driven corresponding to each of the laser beams is disposed between the reflective mirror and the lens, and a scanning line interval between the plurality of imaging spot rows can be adjusted. An optical recording apparatus characterized by being configured as described above. A plurality of beam generating light sources that emit laser light, a photosensitive drum that is formed so that a plurality of imaging spot rows that are imaged by scanning of the laser light are arranged on an outer peripheral surface, and the plurality of imaging spot rows are formed In a multi-beam scanning optical recording apparatus having an optical system for transmitting the laser light,
A reflective element array including a micromirror array that can be driven corresponding to each laser beam is provided in the optical system,
A beam interval detector for detecting a scanning line interval between the plurality of imaging spot rows is provided;
An optical recording apparatus characterized by adjusting a scanning line interval between the plurality of imaging spot rows by controlling a reflection element array in accordance with detection by the beam interval detection device. 2. The reflection element array including a micromirror array for independently reflecting individual laser beams emitted from a plurality of beam generation light sources is provided at a position satisfying the following expression. Optical recording device.

Where L is the distance from the multiple beam generating light source to the position where the micromirror array is arranged δFA is the size of each light emitting portion of the multiple beam generating light source and 1 / (e ² ) of the center light intensity
Level half width λ: Light source wavelength dFA: Interval between light emitting portions of a plurality of beam generating light sources. A semiconductor laser module section for entering light emitted from a plurality of independent semiconductor lasers into each optical fiber corresponding to the semiconductor laser and a light emitting side tip of each optical fiber are close to each other in a row The optical recording apparatus according to claim 1, further comprising: an optical fiber array disposed on the optical fiber array, wherein the light emitted from the optical fiber array is used as a light source for generating a plurality of beams.

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