JP3522538B2 - Multi-beam writing optical system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam writing optical system.

[0002]

2. Description of the Related Art In a writing optical system of an optical scanning system used in a writing system of a digital copying apparatus, a laser printer, etc.,
Light beams from a plurality of light emitting portions that can be independently light-modulated are focused on a surface to be scanned, for example, a photoconductor surface, as beam spots separated in the sub-scanning direction, and a plurality of scanning lines on the surface to be scanned are simultaneously scanned. It is intended to put such a multi-beam writing optical system into practical use. In a multi-beam scanning device, if the pitch between scanning lines that are simultaneously scanned (scanning line spacing in the sub-scanning direction; hereinafter referred to as "scanning line pitch") is unstable, the quality of the formed image deteriorates. Therefore, various techniques for keeping the scanning line pitch stable have been proposed. For example, in the multi-beam writing optical system described in Japanese Patent Application Laid-Open No. 7-209596, two laser diodes in which light emitting portions are arranged at intervals of 25 μm in the sub scanning direction are used as a plurality of light sources, and two light beams emitted from these laser diodes are emitted. , "Telecentric in the sub-scanning direction" is a scanning imaging optical system that simultaneously reflects the deflected beam on the surface to be scanned by simultaneously reflecting it on the same surface of a polygon mirror that is a deflector through an aperture for beam shaping and a cylindrical lens. By doing so, the chief ray of each light beam after the scanning and imaging optical system is made substantially parallel to the optical axis of the device in the sub-scanning direction to stabilize the scanning line pitch. In addition, Japanese Patent Laid-Open No. 6-1
In the multi-beam writing optical system described in Japanese Patent No. 8802, a plurality of light beams emitted from a light source having a plurality of light emitting portions in the sub-scanning direction are passed through an aperture portion of an aperture, and have an optical power in the sub-scanning direction. The morphic optical system forms an image on the deflecting / reflecting surface of the deflector, and the deflected light beam is converged as a beam spot on the surface to be scanned by the scanning image forming optical system to simultaneously scan a plurality of scanning lines. , The anamorphic optical system makes "the above-mentioned aperture and the imaging optical system in a conjugate relationship", and the aperture side is made the same magnification or reduction side, so that the light beam that passes off-axis among the multiple light beams Is emitted from the optical axis of the image forming optical system without being significantly separated from the optical axis, thereby stabilizing the scanning line pitch.

Since the multi-beam writing optical system described in Japanese Patent Laid-Open No. 7-209596 has a special optical arrangement called "telecentric in the sub-scanning direction" as described above, the optical system becomes large. There is. That is, in order to make it telecentric on the exit side, two light beams are crossed at the object side (light source side) focal position of the scanning imaging optical system. For this purpose, the aperture of the beam shaping aperture and the above It is necessary to make the focal position and the conjugate with each other by the cylindrical lens, and therefore the distance between the cylindrical lens and the opening must be increased, and the part on the light source side of the multi-beam writing optical system becomes large. . It is possible to increase the power of the cylindrical lens to shorten the distance between the cylindrical lens and the aperture as much as possible, but there is a limit to increasing the power without deteriorating the aberration, and miniaturization of the multi-beam writing optical system is not possible. difficult. In the multi-beam writing optical system described in Japanese Patent Application Laid-Open No. 6-18802, since the aperture and the scanning imaging optical system are conjugated, there is no effect when the aperture and the emission position are different, and it can be applied. The optics will be limited.

[0004]

SUMMARY OF THE INVENTION According to the present invention, the range in which the fidelity of image formation can be maintained in practice for the scanning line bending and pitch deviation of a plurality of light beams on the surface to be scanned without enlarging the optical system. It is an object of the present invention to provide a multi-beam writing optical system that can be reduced to

[0005]

A multi-beam writing optical system according to the present invention is a "multi-beam which simultaneously scans a plurality of scanning lines in a main scanning direction by a plurality of light beams separated in a sub-scanning direction on a surface to be scanned. And a plurality of light emitting portions, a plurality of coupling optical systems, a first image forming system, an optical deflector, and a second image forming system ( claims 1 and 2 ). .
The "plurality of light emitting portions" can be individually modulated, and the light beam from each light emitting portion is focused as a beam spot on the surface to be scanned, and scans one scanning line on the surface to be scanned. As the light emitting portion, an LED can be preferably used in addition to the semiconductor laser described later. Each of the "plurality of coupling optical systems" is provided corresponding to each of the light emitting units. That is, the same number of light emitting units and coupling optical systems are used. Each coupling optical system takes in the light beam emitted from the corresponding light emitting portion and couples it to the following optical system. As the coupling optical system, a coupling lens or a reflecting surface having a similar function, such as a concave mirror, can be used. The “first imaging system” is an optical system that forms an image of a plurality of light beams coupled by a plurality of coupling optical systems in the sub-scanning direction, and includes a convex cylindrical lens, a concave cylindrical mirror, or these. Combinations can be used. The "deflector" is
The first optical system has a deflecting / reflecting surface in the vicinity of the image forming position of the light beam to deflect a plurality of light beams, and a polygon mirror, a rotating two-sided mirror or a rotating single-sided mirror can be used. . The “second image forming system” is an optical system that forms an image of a plurality of light beams deflected by the deflector on a surface to be scanned (actually, the photosensitive surface of a photoconductive photoconductor). 1
It can be configured as one or more lenses, one or more imaging mirrors, or a combination of lenses and imaging mirrors. When the focal length in the sub-scanning direction of the "optical element having the largest positive power in the sub-scanning direction" among the optical elements (lenses and image-forming mirrors) forming the second imaging system is f, a plurality of light beams , Within the range of ± f / 2 from the optical element having the largest positive power in the sub-scanning direction, they intersect in the sub-scanning direction.

[0006] In claim 1 or 2 multibeam write optical system according, each principal rays of a plurality light beams emitted from the plurality of light emitting units with respect to the first imaging system, enters the diverging slightly in the sub-scanning direction ( Claim 3 ). That is, in this case, the chief rays of the plurality of light beams enter the first imaging system while being separated from each other in the sub-scanning direction. In the multi-beam writing optical system according to claim 1 , the light source section that synthesizes and emits a plurality of light beams has the following first and second configurations.
It is configured to have a light source section and a beam combining means.
The "first light source unit" includes an odd number (≧ 1) of semiconductor lasers, an odd number of coupling optical systems provided in pairs with each of the semiconductor lasers to capture a light beam, and positioned at the center in the main scanning direction. And a supporting member for integrally supporting the semiconductor lasers arranged on the “first emission axis”.
The “second light source unit” includes an even number of semiconductor lasers, an even number of coupling optical systems that are provided in pairs with each of the semiconductor lasers, and take in a light beam, and these in the main scanning direction with “second And a supporting member that is symmetrically arranged on the injection axis and integrally supports the same. "Beam combining means"
It is a means for emitting the light beams from the first and second light source units while making them close to each other in the sub-scanning direction. The first emission axis is an emission axis specific to the first light source section, and the second emission axis is an emission axis specific to the second light source section. Therefore, when it is clear which of the first and second light source sections is the emission axis, or when it is necessary to particularly distinguish between the first and second light source sections, it is simply referred to as the emission axis. It should be noted that the “emission axis” is a reference for the emission direction of the light beam and does not have to coincide with the actually emitted light beam. In each of the first and second light source units, the light beam emitted from the semiconductor laser located at a position symmetrical with respect to the emission axis is
It is configured to divergently enter the imaging system in the sub-scanning direction.

The multi-beam writing optical system according to claim 2
The system has a light source part that combines and emits multiple light beams.
It has first and second light source sections and beam combining means.
Configured as Each of the first and second light source units includes "an even number of semiconductor lasers, a plurality of coupling optical systems that are provided in pairs with each of the semiconductor lasers, and take in a light beam, and these are symmetrical about the emission axis in the main scanning direction. sequence and is configured to "and a support member for supporting integrally, these first, a light beam from the second light source unit, the beam combining means, so as to emit in close proximity to the sub-scanning directions been, first, in each of the second light source section, the light beam emitted from the semiconductor laser at the symmetrical positions with respect to the exit axis (principal ray) is, with respect to the first imaging system, the sub-scanning direction Is configured to divergently enter. Request above
In the multi-beam writing optical system according to Item 1, 2 or 3 , each coupling optical system is a “coupling lens”, and the emission point positions of the semiconductor lasers of the first and second light source units are set to the coupling lens. Optical axis is first or second
The side above the emission axis of the coupling lens in the sub-scanning direction is set lower than the optical axis of the coupling lens in the sub-scanning direction, and the optical axis of the coupling lens is the first or second emission axis. The side below in the sub-scanning direction can be set above the optical axis of the coupling lens in the sub-scanning direction ( claim 4 ). Claims 1 to 4 above
In the multi-beam writing optical system described in Arbitrary 1, the action of the coupling optical system may be a "collimating action for converting a light beam emitted from a semiconductor laser into a parallel light beam" ( claim 5 ). Any of claims 1 to 5 above
In the multi-beam writing optical system according to item 1, the light source unit is provided with a "base member that substantially modularizes and holds the first and second light source units and the beam combining means".
The first and second light source units are rotatably supported around a rotation reference that is aligned with the reference optical axis of the optical system after the imaging system, and “each emission axis is the rotation center with respect to the base member. may be rotatable "independently (according
Item 6 ).

In the multi-beam writing optical system according to any one of claims 1 to 6, "the emission axis of the first light source section and the emission axis of the second light source section are predetermined in the main scanning direction. The first and second light source units may be arranged so as to be “angled or separated by a predetermined distance” ( claim 7 ).
In the multi-beam writing optical system according to any one of claims 1 to 7 , "the optical system in which the emission axis of the first light source unit and the emission axis of the second light source unit are after the first imaging system" The first and the second so as to be symmetrical with respect to the reference optical axis in the main scanning direction.
It is possible to provide the light source part ( claim 8 ). In the multi-beam writing optical system according to any one of claims 1 to 8 , "a principal ray of each light beam emitted from a plurality of semiconductor lasers supported by a first light source unit is a deflector Crossing in the main scanning direction near the deflecting and reflecting surface,
Each of the plurality of semiconductor lasers is set so that the chief ray of each light beam emitted from the plurality of semiconductor lasers supported by the second light source unit intersects in the main scanning direction in the vicinity of the deflective reflection surface. It is possible ( claim 9 ). The multi-beam optical writing system of claim 9, wherein "a plurality of semiconductor lasers is set shifted in the main scanning direction from the optical axis of the coupling optical system" can (claim 1
0 ).

In the multi-beam writing optical system according to any one of claims 1 to 10 , "the first exit axis and the second exit axis are in the main scanning direction near the deflection reflection surface of the optical deflector. The optical axis intersects the emission axis of the first light source unit and the second
The emission axis of the light source part of, makes a predetermined angle in the main scanning direction,
Alternatively, the first and second light source units can be arranged so as to be separated by a predetermined distance in the main scanning direction ( claim 1).
1 ). First and second injection axes, namely first and second
The term "optically intersects" the emission axis of the light source section means that the emission axis is virtually regarded as a light beam and is crossed when the first image forming system or the like receives an optical action. Request above
In the multi-beam writing optical system according to any one of items 1 to 11, in a pair of a semiconductor laser and a coupling optical system that are symmetric with respect to each emission axis of the first and second light source units, The amount of shift from the optical axis of the coupling optical system of the semiconductor laser can be made equal ”( claim 1
2 ). Further, in the multi-beam light source device according to any one of claims 1 to 12 , "the emission axis of the first light source section and the emission axis of the second light source section are substantially in the sub-scanning direction after the beam combining means. "Match" ( claim 13 ). The digital copying apparatus according to claim 14.
Is the multibee according to any one of claims 1 to 13 above.
Write to the photoconductive photoconductor using the writing system.
U Further, the laser printer according to claim 15 is
1 to 13 in the multi-beam writing optical system
Thus, the photoconductive photoconductor is scanned to perform writing.

[0010]

FIG. 1 shows a multi-beam scanning device using a multi-beam writing optical system as one embodiment of the multi-beam writing optical system of the present invention.
In this embodiment, the light source section 301 uses four semiconductor lasers as a light emitting section and emits four light beams. (In order to avoid complication of the figure, the number of light beams in the figure is simplified and shown. The four light beams emitted from the light source unit 301 can be individually modulated.
The laser beams are emitted from two semiconductor lasers and are respectively coupled by a coupling optical system, and are incident on a cylindrical lens 302 as a “first image forming system”, focused by the lens 302 in the sub scanning direction, and sub-scanned by each other. The image is formed as a "long line image in the main scanning direction" separated in the scanning direction.
The polygon mirror 303 as a "deflector" has a deflecting / reflecting surface in the vicinity of the image forming position of the above-mentioned line image, and rotates at a constant speed to 4
The light beams of the book are deflected simultaneously and at a constant angular velocity. The four deflected light beams are “mutually mutually” on the photosensitive surface 309a of the photoconductive photosensitive member 309 which is the substance of the “scanned surface” by the action of the lenses 304 and 308 which form the “second imaging system”. The light is condensed as four beam spots separated in the sub-scanning direction, and the photosensitive surface 309a is simultaneously scanned with four scanning lines to perform writing. The optical path of the deflected light beam is reflected by the folding mirror 30.
Bent by 7. The deflected light beam traveling toward the scanning region is reflected by the mirror 305 toward the detector 306. When the detector 306 detects the light beam, it emits a synchronization detection signal, and the write start timing is based on this synchronization detection signal. Be taken. On the other hand, the output of the detector 306 is sent to the pitch calculator 311. The pitch calculator 311 calculates the interval between the four light beams in the sub-scanning direction, calculates the pitch correction amount for correcting the scanning line pitch based on this, and sends it to the motor controller 312. The motor control unit 312 controls the motor 310 according to the pitch correction charge, presses the contact portion 203-2 provided on the light source unit 301 to rotate the light source unit 301, and causes a desired surface to be scanned on the surface to be scanned. The position of the light source unit 301 is adjusted so that the scanning line pitch can be obtained.

FIG. 2 is an exploded perspective view for explaining the light source unit 301 in the embodiment shown in FIG. Figure 2
In the figure, the semiconductor lasers 101 and 102 are arranged on the back side of the aluminum die-cast support member 103 in the main scanning direction.
They are press-fitted and supported in fitting holes (not shown) formed in parallel at mm intervals. Coupling lenses 104 and 105 as a coupling optical system are “collimating lenses”, which are provided corresponding to the semiconductor lasers 101 and 102, respectively. That is, the coupling lens 104,
Reference numeral 105 denotes the X position in the optical axis direction so that the divergent light beam from the corresponding semiconductor laser becomes a parallel light beam, and the Y, Z positions so that the collimated parallel light beam has a predetermined beam emission direction. Adjusted, U-shaped support 1
It is fixed to 03-1 and 103-2 with a UV curing adhesive. In this way, the semiconductor laser 10 is attached to the support member 103.
The assembly of the first and second coupling lenses 104 and 105 is the "first light source section". Similarly, the semiconductor lasers 111 and 112 are press-fitted and supported in fitting holes formed in parallel with each other in the main scanning direction at intervals of 8 mm on the back side of the support member 113 made of aluminum die cast. Coupling lenses 114 and 115 as a coupling optical system are collimating lenses, and semiconductor lasers 111 and 115, respectively.
It is provided corresponding to 112. That is, the coupling lenses 114 and 115 set the X position in the optical axis direction so that the divergent light beam from the corresponding semiconductor laser becomes a parallel light beam, and the emission direction of the emitted light beam becomes a predetermined beam emission direction. The Y and Z positions are adjusted, and the U-shaped support portion 113-
1 and 113-2 are fixed with a UV curing adhesive. In this way, the semiconductor lasers 111 and 11 are attached to the support member 113.
The assembly of 2 and the coupling lenses 114 and 115 is the "second light source section".

In the first and second light source portions, the cylindrical portions 103-3 and 113-3 of the supporting members 103 and 113 are fitted into the fitting holes 201-1 and 201-2 of the base member 201, respectively, and the base is formed. The member 201 is fixed to the back side through the screw from the front side. The prism 202 as the “beam combining means” includes the half-wave plate 202-1 and the polarization separation film 2.
02-3, and are bonded and fixed to the front surface of the base member 201. Semiconductor laser 10 provided in the first light source section
1, 102 are set so that the polarization state of the light beams emitted from them is approximately P-polarized with respect to the polarization separation film 202-3. Therefore, the semiconductor laser 101,
The light beam from 102 is coupled to the coupling lens 104,
After being collimated by 105, the light is transmitted through the polarization separation film 202-3 of the prism 202. The semiconductor lasers 111 and 112 provided in the second light source unit are set so that the polarization state of the light beam emitted from them is substantially P-polarized with respect to the polarization separation film 202-3. Semiconductor laser 1
The light beams from 11, 112 are coupling lenses 11
After being collimated by 4,115, the half-wave plate 20
After passing through 2-1, the polarization plane is rotated by 90 degrees to become S-polarized light with respect to the polarization separation film 202-3, reflected by the reflection surface 202-2 of the prism 202, and then the polarization separation film 202.
It is reflected at -3 and is emitted from the prism 202. In this way, the semiconductor lasers 101, 102, 111, 11
2 is emitted from the corresponding coupling lens 104,
The four light beams collimated by 105, 114, and 115 are brought close to each other in the sub-scanning direction, and the prism 202
Shoot out from. First and second light source units and prism 20
The base member 201 equipped with 2 and 3 is assembled and fixed to the holder 203. The four light beams emitted from the prism 202 are emitted from the emission unit 203-1 of the holder 203. An imaginary axis C passing through the center of the injection unit 203-1 is the "rotation reference". That is, when the motor 310 shown in FIG. 1 is controlled to press the contact portion 203-2 provided in the light source unit 301 to rotate the light source unit 301, the “light source unit” rotates about the rotation reference C as an axis. To do. The rotation reference C is matched with the "reference optical axis of the optical system after the first imaging system".

That is, the light source section (hereinafter referred to as "light source unit") shown in FIG. 2 has an even number of semiconductor lasers 101,1.
02, and a plurality of coupling optical systems 104 and 10 provided in pairs with each of these semiconductor lasers to capture a light beam.
5, a first light source section having a supporting member 103 integrally supporting them, a second light source section similar to the first light source section, and light beams from the first and second light source sections Beam synthesizing means 202 for irradiating each of them with each other in the sub-scanning direction. FIG. 3 shows another embodiment of the light source unit (another “light source unit”). This light source unit uses three semiconductor lasers as a plurality of light emitting units. To avoid complications, the same as in Figure 2,
Items that are not likely to be confused are given the same reference numerals as in FIG. 2, and description thereof will be omitted. The light source unit of FIG. 3 is different from the light source unit of FIG. 2 in the first light source unit. That is, in FIG.
The first light source unit has one semiconductor laser 121, a support member 123, and a coupling lens 122. The semiconductor laser 121 is a support member 1 made of aluminum die cast.
It is press-fitted and supported in a fitting hole (not shown) formed in the central portion of the support member on the back side of 23. Coupling lens 12
A collimator lens 2 is provided corresponding to the semiconductor laser 121. That is, the coupling lens 122 sets the X position in the optical axis direction so that the divergent light beam from the corresponding semiconductor laser 121 becomes a parallel light beam, and the Y direction so that the beam emission direction coincides with the optical axis of the coupling lens 122. ,
The Z position is adjusted, and it is fixed to the U-shaped support portion with a UV curing adhesive. The first and second light source units are provided on the base member 201, as in the light source unit of FIG. 2, and are provided with a half-wave plate 202-1 and a polarization separation film 202-3.
The prism 202 including and is bonded and fixed to the front surface of the base member 201. The semiconductor laser 122 provided in the first light source unit is set so that the polarization state of the light beam emitted from them is substantially P-polarized with respect to the polarization separation film 202-3, and the light from the semiconductor laser 121 is emitted. The beam is collimated by the coupling lens 122 and then passes through the polarization separation film 202-3 of the prism 202. The light beams from the semiconductor lasers 111 and 112 provided in the second light source unit are collimated by the coupling lenses 114 and 115, and then transmitted through the ½ wavelength plate 202-1 so that the polarization plane is rotated by 90 degrees. , Becomes S-polarized with respect to the polarization separation film 202-3, is reflected by the reflection surface 202-2 of the prism 202, is reflected by the polarization separation film 202-3, and is reflected by the prism 2
Eject from 02. In this way, the semiconductor laser 12
3 radiated from 1, 111, 112 and collimated by the corresponding coupling lenses 122, 114, 115
The light beams of the book are made close to each other in the sub-scanning direction and emitted from the prism 202. The base member 201 equipped with the first and second light source units and the prism 202 is the holder 2
It is assembled and fixed to 03. The three light beams emitted from the prism 202 are emitted from the emission unit 203-1 of the holder 203. A virtual axis passing through the center of the injection unit 203-1 is the rotation reference C. That is, the light source unit shown in FIG. 3 has an odd number of semiconductor lasers 121, an odd number of coupling optical systems 122 that are provided in pairs with the semiconductor lasers 121 and take in a light beam, and the semiconductor lasers 121 with a first emission axis. A first light source unit having a support member 123 arranged above and integrally supporting them, and an even number of semiconductor lasers 111,
112, and an even number of coupling optical systems 11 that are provided as a pair with each of these semiconductor lasers and take in a light beam.
4, 115 and a second light source unit having support members 113 that are arranged symmetrically with respect to the second emission axis in the main scanning direction and integrally support the first and second light source units. Beam synthesizing means 202 for emitting the light beams of (1) and (2) approaching each other in the sub-scanning direction.

FIG. 4A shows an XY section of the light source unit shown in FIG. The Y direction is the main scanning direction, the X direction is the optical axis direction of the first imaging system, and the rotation reference C
Parallel to. In FIG. 4A, reference numeral a1 is the first
Shows the "emission axis" of the light source section, and reference numeral a2 shows the "emission axis" of the second light source section. The injection axis a1 is the central axis of the cylindrical portion 103-3 of the support member 103 shown in FIG.
The injection axis a2 is the cylindrical portion 1 of the support member 113 shown in FIG.
13-3 is the central axis. Semiconductor lasers 101 and 1
02 and the coupling lenses 104 and 105 are arranged symmetrically with respect to the emission axis a1. Although not shown in FIG. 4A, the semiconductor lasers 111 and 112 and the coupling lenses 114 and 115 respectively have an emission axis a2.
They are arranged symmetrically with respect to. In the embodiment described, the X position of each coupling lens is set so that the light beam emitted from the semiconductor laser becomes a parallel light beam, but of course, the position of the coupling optical system is not limited to this. Not something. If the action of each coupling lens is a collimating action as in this embodiment ( Claim 5 ), the light beam coupled to enter the cylindrical lens (302 in FIG. 1) as the first imaging element. Is a parallel light flux, and the distance from the coupling lens to the cylindrical lens can be set freely,
High degree of freedom in optical system layout.

FIG. 4B shows the arrangement of the semiconductor lasers in the first and second light source sections as viewed from the direction of the rotation reference C. As shown in the figure, the injection axes a1 and a2
Are arranged so as not to coincide with the main scanning direction (vertical direction in the drawing) and separated by a predetermined distance m (for example, 1 mm, but this interval differs depending on the scanning optical system) in the main scanning direction. The plane parallel to the sub-scanning direction "
1 and a2 are set to be symmetrical ( claim
8 ). Further, as shown in FIG.
1, a2 (projection of the a2 onto the XY plane) are not parallel to each other,
“Predetermined angle β with each other” in the direction intersecting with the rotation reference C
( Claim 7 ). The angle β is the injection axis a1, a2
Intersections are set to be "deflecting reflection surface near the polygon mirror (303 in FIG. 1)" (Claim 1
1 ). Since the emission axes a1 and a2 cross each other in the main scanning direction as described above, in this embodiment, the support surface of the base member 201 serving as the mounting reference surface of each of the first and second light source units is Each with respect to the rotation reference C,
Each β / 2 is inclined (β1 = β2 = β / 2).

That is, in FIG. 5A, reference numeral 110-
Reference numeral 3 indicates a "reference surface for attachment to the first light source portion" of the base member (reference numeral 201 in FIG. 2). The injection axis a1 is orthogonal to the mounting reference plane 110-3,
Since -3 has an angle β1 with respect to the direction orthogonal to the rotation reference C, the injection axis a1 has an angle β1 with respect to the rotation reference C.
It will be inclined by (= β / 2). In FIG. 5B, reference numeral C ′ is a straight line obtained by causing the rotation reference C to be reflected by the polarization splitting film and the reflecting surface of the prism 202. The mounting reference surface 110-4 for the second light source unit is inclined with respect to the axis C ′, and the inclination angle causes the emission axis a2 to be inclined with respect to the axis C ′ by an angle β2 (= β / 2). It has become.
Therefore, when the emission axis a2 is optically reflected by the reflection surface of the prism 202 and the polarization separation film, the emission axis a2 is inclined by the angle β2 with respect to the rotation reference C. The inclinations of the injection axes a1 and a2 with respect to the rotation reference C are opposite to each other.
1 and a2 form an angle β with each other. The adjustment of the scanning line pitch (distance between adjacent beam spots in the sub-scanning direction in the sub-scanning direction) on the surface to be scanned is based on the fitting hole when fixing the first and second light source parts to the base member. Are tilt angles θ1 and θ of the semiconductor lasers with respect to the main scanning direction.
2 performed by adjusting the (see FIG. 4 (b)) (claim
6 ). Furthermore, the distance R in the sub-scanning direction between the ejection axes a1 and a2
(See FIG. 4B) is set to be the same as the pitch of the prism 202 in the sub-scanning direction (the distance between the reflecting surface 202-2 of the prism 202 and the polarization separation film 202-3 in the sub-scanning direction). Therefore, the emission axis a of the first light source unit
The emission axis a2 of the first light source unit and the emission axis a2 of the second light source unit substantially coincide with each other in the sub-scanning direction after emission from the prism 202 which is the beam combining means (positioned in the same plane parallel to the XY plane in FIG. 4A). ( Claim 13 ).

A specific pitch adjusting method will be described below. FIG. 6 shows a state in which the positional relationship between the semiconductor laser and the optical axis of the coupling lens in the light source unit described with reference to FIG. 2 is viewed from the direction of the rotation reference C. The Y positions of the coupling lenses 104 and 105 with respect to the main scanning direction (horizontal direction in the drawing) are the semiconductor lasers 101 and 102.
The chief ray emitted from the polygon mirror (30 in FIG.
The distances ζ101 and ζ102 in the figure are determined so as to intersect in the main scanning direction in the vicinity of the deflecting reflection surface of 3) ( claim 10 ).
The distance ζ 101 is the amount of deviation in the Y direction between the light emitting portion of the semiconductor laser 101 and the optical axis of the coupling lens 104,
The distance ζ 102 is the amount of deviation in the Y direction between the light emitting portion of the semiconductor laser 101 and the optical axis of the coupling lens 105.
At this time, as shown in FIG. 5A, the angles α1 and α2 formed by the emission axis a1 and the principal rays of the light beams coupled by the coupling lenses 104 and 105 are equal. The reason why the Y position of the coupling lens is set in this way is to reduce the inner diameter of the polygon mirror 303. In this embodiment, the semiconductor lasers 101 and 102 are Y
Since there is an interval of 8 mm in the direction, the Y positions of the collimator lenses 104 and 105 (the above ζ101 and ζ102)
If is not set appropriately, the two light beams are largely separated in the main scanning direction at the position of the deflecting / reflecting surface of the polygon mirror, and the deflecting / reflecting surface must be increased in order to scan a desired scanning width. The inner diameter of the polygon mirror must be increased. This not only causes an increase in cost, but also causes an adverse effect on downsizing of the optical scanning device, and causes a problem of noise and vibration.

Next, as for the Z position (position in the sub-scanning direction) of the coupling lens, as shown in FIG. 6, the light emitting portions of the semiconductor lasers 101 and 102 are shifted with respect to the optical axes of the collimator lenses 104 and 105. The quantities δ101 and δ1
02 is set to be the same amount ( claim 12 ).
In this way, ζ101 = ζ102 for the Y position
Therefore, ε101 = ε10 for the Z position as well.
The relationship of 2 will be established. The Z position is set in this way so that the scanning line pitch on the surface to be scanned (309a in FIG. 1) is not asymmetric.

The above-mentioned "X, Y, Z alignment" is the same for the second light source unit, and the coupling lens 114,
The X position of 115 corresponds to each of the semiconductor lasers 111 and 112.
So that the divergent light flux of is a parallel light flux, the Z position is set so that the chief ray of the light beams from the semiconductor lasers 111 and 112 "crosses in the main scanning direction in the vicinity of the deflecting reflection surface of the polygon mirror". The shift amounts δ111 and δ112 of the light emitting portions of the semiconductor lasers 111 and 112 with respect to the optical axes of the coupling lenses 114 and 115 are set to be the same. FIG. 7 shows the positional relationship of four beam spots at an "arbitrary moment" on the surface to be scanned.
LD1-L, LD1-R, and LD2 are beam spots obtained by focusing light beams emitted from the semiconductor lasers 101, 102, 111, and 112 on the surface to be scanned, respectively.
-L, LD2-R. As described above, the sub-scanning pitches P1, P2, P3 on the surface to be scanned are adjusted by adjusting the X, Y, Z positions of the coupling lens and filling and fixing the UV curable adhesive. When fixing the second light source unit to the base member, by adjusting the inclinations θ1 and θ2 (FIG. 4B) of the semiconductor lasers from the main scanning direction with reference to the fitting hole, as shown in FIG. The beam spot LD1
The pitch P2 is formed by -R and LD1-L, and the pitch P1 + P2 + P3 is formed by the beam spots LD2-R and LD2-L.
To form. At this time, when δ101 ≠ δ102, δ111
When ≠ δ112, ε101 ≠ ε102, ε111 ≠
ε112, and the pitches P1 and P3 are not the desired pitches. This is because, as shown in FIG. 8, if the shift amount on the light source side is different, the apparent sub-scanning direction component generated by the rotation angles θ1 and θ2 is different, and as shown in FIG. And the center O of LD1-L,
And the center O'of the beam spots LD2-R and LD2-L
Are displaced from each other in the sub-scanning direction. If this shift amount is set to 0, P1 = P2 = P3 as shown in FIG. 7B, but only by adjusting the rotation of the first and second light source units on the light source side,
The amount of deviation cannot be set to 0, and pitches P1 and P3
Becomes asymmetrical (different in size). The "pitch asymmetry on the surface to be scanned" described above is because the shift amounts on the light source side are different from each other as δ101 ≠ δ102 and δ111 ≠ δ112.
This can be improved by setting the same shift amount for each semiconductor laser with respect to the corresponding coupling lens optical axis, such as 101 = δ102 and δ111 = δ112.

As described above, in the embodiment being described, the emission axes a1 and a2 are not parallel to each other, and have a predetermined angle β in the direction intersecting the rotation reference C of the holder 203 in the main scanning direction. is doing. FIG. 9A shows four beam spots LD1-L, LD1-R, L on the surface to be scanned when the emission axes a1 and a2 are parallel to each other.
The positional relationship between D2-L and LD2-R is shown. (B) shows the above four beams on the surface to be scanned when the emission axes a1 and a2 are at a predetermined angle β and intersect in the main scanning direction. The positional relationship of the spots is shown. In (a), the injection axis a1,
The arrival points O and O'of a2 on the surface to be scanned coincide with each other.
The Y position of each coupling lens is set so that the principal ray of the light beam emitted from each semiconductor laser of the first light source unit intersects in the main scanning direction near the reflecting surface of the polygon mirror (ζ1
01 = ζ 102), and the chief ray of the light beam emitted from each semiconductor laser of the second light source unit intersects in the main scanning direction near the reflecting surface of the polygon mirror (ζ 111 = ζ).
112) It is set. Strictly speaking, the relationship between ζ 101 and ζ 111 (or the relationship between ζ 102 and ζ 112) is ζ 10
1 ≠ ζ111 (or ζ102 ≠ ζ112),
This difference is due to the fact that the optical path of the light beam emitted from the semiconductor laser of the second light source section is lengthened by the pitch R of the prism 202 in the sub-scanning direction and is extremely small. Therefore, even when the four light beams reach the surface to be scanned, the beam spots LD1-R and LD2-R and the beam spots LD1-L and LD2-L are in the main scanning direction as shown in (a). Are approximately the same position. In this way, when the two beam spots form a pair and are located at substantially the same position in the main scanning direction, the synchronization signal of each light beam (detected in the vicinity of the image formation position of the beam spot) is independently detected. I can't. In order to be able to detect each light beam independently, each beam spot needs to be “separated to some extent in the main scanning direction”. Figure 9
As in (a), the beam spots LD1-L and LD2-
L almost overlaps in the main scanning direction, and the beam spot LD1-
The reason why R and LD2-R almost overlap in the main scanning direction is that the emission axes a1 and a2 are set to be parallel to each other on the light source side. In the embodiment described, as described above, the emission axes a1 and a2 intersect each other at the predetermined angle β in the main scanning direction. In this way, as the emission axes a1 and a2 are crossed in the main scanning direction,
As shown in FIG. 9B, the beam spots LD1-L and LD
2-L, beam spots LD1-R and LD2-R are separated from each other in the main scanning direction and can be detected independently. The angle β formed by the emission axes a1 and a2 in the main scanning direction is set such that the intersection position of the emission axes a1 and a2 is in the vicinity of the deflective reflection surface of the polygon mirror. By doing so, the principal rays of the light beams from the semiconductor lasers 101 and 102 and the principal rays of the light beams from the semiconductor lasers 111 and 112 all overlap in the vicinity of the deflective reflection surface. Therefore, the deflecting / reflecting surface of the polygon mirror can be downsized, and the inner diameter of the polygon mirror can be minimized. Further, by making the reflection points of the four principal rays by the polygon mirrors substantially coincide with each other, the four principal rays reaching the same image height on the surface to be scanned (the position where the beam spots are the same in the main scanning direction) are reached. The chief ray will pass through the same position of each optical element (304, 307, 308 in FIG. 1) of the second imaging system in the main scanning direction, and thus the second ray for the four light beams will be transmitted.
Since the power of the image forming system is the same, the behavior of the field curvature is uniform for each light beam. If only two principal rays overlap each other (when the emission axes a1 and a2 are parallel),
Although the field curvature behavior with respect to the light beams from the semiconductor lasers 101 and 102 in the first light source section is the same, the field curvature behavior with respect to the light beams from the semiconductor lasers 111 and 112 in the second light source section is the same. The same)), for example, the behavior of the field curvature with respect to the light beams from the semiconductor lasers 101 and 111 is different from each other due to the deviation of the polygon mirror reflection points in the main scanning direction. From this point of view, it is desirable to set the angle β so that the intersection of the emission axes a1 and a2 is near the reflection surface of the polygon mirror as in the embodiment described above.

As described above, in this embodiment, the distance R of the emission axes a1 and a2 in the sub-scanning direction is set to be the same as the pitch of the prism 202 in the sub-scanning direction.
FIG. 10A is a diagram schematically showing a case where the distance R of the emission axes a1 and a2 in the sub-scanning direction is shorter than the pitch of the prism 202 in the sub-scanning direction (“prism pitch” in the figure). 11A is a diagram schematically showing a case where R matches the pitch of the prism in the sub-scanning direction.

In the case of FIG. 10A, the principal rays of the light beams emitted from the semiconductor lasers 111 and 112 of the second light source section are, after the prism 202, in the sub-scanning direction of each optical element (vertical direction in the figure). Fig. 1 shows the passing height of).
0 (b) (the emission axis a1 is set to coincide with the optical axis of each optical element after the polygon, and therefore the principal ray of the light beam emitted from the semiconductor lasers 101 and 102 of the first light source unit is , Through the heights symmetrical with respect to the optical axis of each optical element (the principal rays of the light beams from the semiconductor lasers 101 and 102 are not shown in order to avoid complexity of the drawing).

As shown in FIG. 10B, when the distance R does not match the pitch of the prism 202 in the sub-scanning direction, the two light beams that have passed through the prism 202 are the ones after the polygon mirror. For each optical element, the light passes through “a height that is asymmetric in the sub-scanning direction”. Therefore, the refractive power of each optical element for these two light beams is different,
The bending amount of the scanning line on the surface to be scanned becomes asymmetric. For this reason, the pitch deviation of the scanning lines becomes asymmetric, which adversely affects the reproducibility of recorded images. Pitch deviation is 2 on the scanned surface
When the maximum value of the interval h between two adjacent scanning lines is h1 and the minimum value thereof is h2, it is defined as the difference between them. The above-mentioned "pitch deviation becomes asymmetric" means that each pitch deviation Δ of the scanning line scanned by the light spot by the light beam emitted from the semiconductor laser 101, 102, 111, 112.
h1 (pitch deviation of scanning line due to 101 and 102), Δ
h2 (pitch deviation of scanning line due to 102 and 111), Δ
This means that h3 (scan line pitch deviation due to 111 and 112) are all different. The asymmetry of pitch deviation is
Contrary to the above, the emission axis a2 is made to coincide with the optical axis of each optical element after the polygon mirror, and the semiconductor lasers 111 and 11 are
Even if the heights of the two light beams passing through the optical element in the sub-scanning direction are made symmetrical, this does not solve the problem. At this time, the heights of the light beams from the semiconductor lasers 101 and 102 passing through the optical element are asymmetric in the sub-scanning direction, and the pitch deviation of the scanning lines is also asymmetrical. The asymmetry of the scanning line pitch is that the emission axes a1 and a2 on the light source side are
It is caused by the misalignment in the sub-scanning direction from 2 onward. In the embodiment in the description, as shown in FIG. 11A, by making the distance R of the emission axes a1 and a2 in the sub-scanning direction coincide with the pitch of the prisms in the sub-scanning direction, the emission axes a1 and a2. Is aligned with the sub-scanning direction after the prism 202. At this time, the semiconductor lasers 111 and 112
As shown in FIG. 11B, the height at which the principal ray of the light beam emitted from the optical element passes in the sub-scanning direction is symmetrical with respect to the optical axis. Further, the principal rays of the light beams from the semiconductor lasers 101 and 102 also have optical element passing heights in the sub-scanning direction that are symmetrical with respect to the optical axis.
= Δh2 = Δh3.

Furthermore, in this embodiment, when the optical system of the light source section is viewed from the sub-scanning direction, the relationship between the emission point position of the semiconductor laser and the optical axis of the coupling lens which forms a pair with the emission point position of the semiconductor laser is Regarding the side where the optical axis of the ring lens is above the first or second emission axis in the sub scanning direction, the optical axis of the coupling lens is below the optical axis of the coupling lens in the sub scanning direction. On the side below the first or second emission axis in the sub-scanning direction, is set above the optical axis of the coupling lens in the sub-scanning direction ( claim 4 ). That is, referring to FIG. 8, the optical axis AX1 of the coupling lens 104 which is paired with the semiconductor laser 101 (the drawing shows a light emitting portion) is above the emission axis a1. At this time, (the light emitting portion of) the semiconductor laser 101
Is set to be below the optical axis AX1. On the other hand, the optical axis AX2 of the coupling lens 105 is below the emission axis a1. At this time, the semiconductor laser 102
The (light emitting portion of) is set to be above the optical axis AX2. The apparent sub-scan shift amount in this state is P2 / (2ω), where ω is the pitch P2 on the surface to be scanned and ω is the lateral magnification of the entire optical system. The same applies to the second light source unit. That is, since the optical axis of the coupling lens 114 paired with the semiconductor laser 111 is above the emission axis a2, the semiconductor laser 111 (the light emitting portion thereof) is below the optical axis of the coupling lens 114. Set to. Further, since the optical axis of the coupling lens 115 is below the emission axis a2, the semiconductor laser 1
12 (the light emitting portion thereof) is set to be above the optical axis. In the case of the second light source unit, the apparent sub-scan shift amount in this state is (P1 + P2 + P3) / (2
ω). The positional relationship between the semiconductor laser and the coupling lens is left / right, upside down and above,
The same effect can be obtained by setting the above relationship (the relationship described in claim 4 ).

In the case of this configuration, the tilt angles θ1 and θ2 of each light source section with respect to the main scanning direction (Y direction) shown in FIG. 4B.
The Z position of the coupling lens may be determined as follows in order to achieve the above relationship by adjusting the. That is, in FIG. 6, for the shift amounts ε101 to ε114 of the optical axis of the coupling lens and the semiconductor laser, for the semiconductor lasers 101 and 102, ε101 = ε102 ≧ P2 / (2ω), and The values 111 and 112 are set so that ε111 = ε112 ≧ (P1 + P2 + P3) / (2ω). With such a setting, thereafter, the rotations θ1 and θ2 of the light source units respectively cause the semiconductor sub-scan shift amount to keep the above relationship (the relationship according to claim 5) as shown in FIG. Laser 101
And 102 are P2 / (2ω), and the semiconductor lasers 111 and 112 are (P1 + P2 + P).
3) / (2ω) can be adjusted. By adjusting in this manner, the chief ray incident on the cylindrical lens (302 in FIG. 1) is emitted from the semiconductor lasers 101 and 1
About 02, semiconductor lasers 111 and 112
Can be divergent ( claim 1,
3 ).

For comparison, as shown in FIG. 12A, the optical axis of the coupling lens and the shift amount ε of the semiconductor laser are preset.
For the semiconductor lasers 101 and 102,
For the semiconductor lasers 111 and 112, ε111 = ε1 so that 101 = ε102 <P2 / (2ω).
12 <(P1 + P2 + P3) / (2ω) is set (ε101 = ε102 = ε111 in FIG. 12A).
= Ε112 = 0), and thereafter, the apparent sub-scan shift amount as shown in FIG. 12B is P2 / (for the semiconductor lasers 101 and 102) due to the rotation angles θ1 and θ2 of the first and second light source units. 2ω) so that the semiconductor laser 11
For 1 and 112, (P1 + P2 + P3) / (2ω)
It is assumed that the adjustment is made so that At this time, when the optical system of the light source unit is viewed from the sub-scanning direction, the relationship between the semiconductor laser and the optical axis of the coupling lens paired with the semiconductor laser is that the optical axis of the coupling lens is the first or second emission. Regarding the side above the axis in the sub-scanning direction, the semiconductor laser is above the optical axis of the coupling lens in the sub-scanning direction, and the optical axis of the coupling lens is above the first or second emission axis. On the side below in the sub-scanning direction, the semiconductor laser is set below the optical axis of the coupling lens in the sub-scanning direction. Then, the principal ray emitted from each semiconductor laser is in the sub-scanning direction, the cylindrical lens 30.
It will be incident on 2 with a focus. Figure 11
As can be seen from (b), when each principal ray is focused on the cylindrical lens in the sub-scanning direction, each light beam passing through the polygon mirror 303 and beyond is higher than each optical element in the sub-scanning direction. You will pass through a high place. Then, the bending of the scanning line for scanning the surface to be scanned becomes large, resulting in an increase in pitch deviation. This increase in pitch deviation is caused by the difference between the pitch deviation between the scanning lines simultaneously scanned by "a certain deflection reflection surface" of the polygon mirror and "the scanning line simultaneously scanned by a certain deflection reflection surface" of the polygon mirror. It is most noticeable in the pitch deviation of the joint of the scanning lines simultaneously scanned by the deflecting / reflecting surface.

In order to reduce the pitch deviation amount,
Of the optical elements forming the second imaging system, four light beams may intersect in the sub-scanning direction, particularly in the vicinity of the optical element having the strongest positive power in the sub-scanning direction. Specifically, assuming that the focal length of the optical element in the sub-scanning direction is f, the position where the four light beams intersect is set within a range of ± f / 2 centering on the optical element. Good ( Claims 1 and 2 ). In the embodiment described, the lens 308 (lens closest to the surface to be scanned) shown in FIG. 1 is the optical element. In FIG. 11, as shown in FIG. 11B, four light beams (two light beams in the figure, but the positions where the light beams intersect are the same) have crossing positions in the sub-scanning direction,
The focal length of the lens 308 (f = 62.21 mm) is largely deviated. In order to keep this within the range of ± f / 2, the position where the four light beams intersect on the light source side of the polygon mirror may be moved to the light source side. That is, as shown in FIG. 13, the cylindrical lens 302
On the other hand, by setting so that the principal ray is incident “divergingly in the sub-scanning direction” ( claim 3 ), it is possible to apparently move the crossing position of the four principal rays to the light source side. Figure 1
In order to make the chief ray divergently enter the cylindrical lens 302 as shown in FIG. 3, the positional relationship between the semiconductor laser and the coupling lens may be set so as to have the configuration shown in FIG. With this setting,
As shown in FIG. 3, since each light beam passing through the polygon mirror 303 and thereafter passes through a portion where the height of each optical element is low in the sub-scanning direction, the bending of the scanning line scanning the surface to be scanned. Can be kept small, and pitch deviation can be reduced.

In the embodiment described above, by properly setting the Y position of the coupling lens,
Two light beams from the same light source unit are made to intersect in the main scanning direction near the reflection surface of the polygon mirror. However, when the number of semiconductor lasers included in the same light source unit increases, the shift amount ζ of the coupling lens located at a position away from the emission axis increases, and as a result, the optical axis of the coupling lens and the overall shift of the semiconductor laser shift. The amount δ also becomes large, and wavefront aberration becomes a problem. The deterioration of the wavefront aberration becomes remarkable as the position of the semiconductor laser moves away from the optical axis of the coupling lens. Deterioration of the wavefront aberration causes a phenomenon of “thickening of the light spot diameter”, which is not preferable in terms of high density and high image quality writing.

FIG. 14 shows another mode in which a plurality of light beams intersect in the main scanning direction in the vicinity of the reflecting surface of the polygon mirror without increasing the shift amount δ. In this embodiment, the fitting hole of the support member 103 (113) is tilted at a predetermined angle in the main scanning direction, and the semiconductor lasers are press-fitted therein. With this arrangement, even if the light emitting portion of the semiconductor laser is positioned on the optical axis of the corresponding coupling lens, both the semiconductor laser and the optical axis of the coupling lens are tilted by a predetermined angle, so that the principal ray of each light beam Can be made to intersect in the vicinity of the deflecting / reflecting surface of the polygon mirror.
Therefore, the shift amount δ can be reduced, and the inner diameter of the polygon mirror can be reduced while avoiding the deterioration of the wavefront aberration. The three-beam light source unit differs from the four-beam light source unit only in the first light source unit, as shown in FIG. In the first light source unit, the semiconductor laser 121 and the coupling lens 122 are arranged on the emission axis, and these are supported by the support member 123. Figure 15
Are light spots LD1, LD2- on the surface to be scanned when the three-beam light source unit shown in FIG. 3 is used.
The sequences of L and LD2-R are shown. To adjust the sub-scanning pitch,
The support member 123 is tilted so that the pitch between the light spots LD2-R and LD2-L is 2P, and the base member 2 is formed.
It is sufficient to fix the first light source unit to 01, and no adjustment is required when fixing the first light source unit. The specific method of pitch adjustment is the same as in the above-described embodiment.

Although the case where the number of semiconductor lasers held in the first and second light source sections is one and two has been described above, three or more semiconductor lasers and coupling lenses are provided in each light source section. When arrayed and held, if the number is odd, the semiconductor laser is arranged on the emission axis similarly to the first light source unit in the light source unit of the above three beams, and the remaining even number of semiconductor lasers are used on the emission axis. The number of the semiconductor lasers and the number of coupling lenses may be even, and if the number of the semiconductor lasers and the number of coupling lenses are even, they may be arranged symmetrically with respect to the emission axis similarly to the second light source section. The specific method of adjustment may be the same as in the embodiment described with reference to FIGS. In the embodiment described above, three lenses are used as the second image forming system, but the present invention is not limited to this, and the second image forming system may be formed of, for example, one lens. Alternatively, a mirror or the like other than the lens can be used as the optical element. Further, in the above embodiment, the semiconductor laser is fixed and the coupling lens is displacement-adjusted to perform mutual positioning, but of course the coupling lens may be fixed and the semiconductor laser may be displaced to perform positioning. Of course, also in this case, the same effect can be obtained if the positioning is performed as described above.

[0031]

As described above, according to the present invention, a novel multi-beam writing optical system can be realized. The multi-beam writing optical system of the present invention can suppress the sub-scanning pitch deviation amount of the scanning lines on the surface to be scanned to a small amount ( contract).
Requirements 1-4 ). Further, according to the invention described in claim 6, since the distance from the coupling lens to the first image forming system can be arbitrarily set, the degree of freedom of the optical system layout is large. Claim
According to the inventions of the items 6 and 8 , even if the light source unit is assembled and then assembled to the optical unit of the optical scanning device, the beam pitch can be corrected to a predetermined value, so that the assembling efficiency is improved and the replacement of only the light source unit becomes possible. The repair cost can be reduced. According to the seventh aspect of the invention , the synchronization signal can be individually detected for a plurality of light spots that simultaneously scan the surface to be scanned. Further, according to the inventions of claims 9 and 10 , the deflecting / reflecting surface of the deflector can be made small, and the deflector can be miniaturized.
In the invention according to claim 11, since the chief rays of the plurality of light beams reaching the same image height pass through the same position of each optical element of the second imaging system in the main scanning direction, the behavior of the field curvature is reduced. It can be aligned with a light beam. Claims 12 and 13
According to the described invention, the asymmetry of the sub-scanning pitch of the scanning lines on the surface to be scanned can be reduced.

[Brief description of drawings]

FIG. 1 is a first embodiment of a multi-beam writing optical system according to the present invention.
It is a figure which shows a form.

FIG. 2 is a diagram for explaining one embodiment of a light source unit used in the multi-beam writing optical system of the present invention.

FIG. 3 is a diagram for explaining another embodiment of the light source unit used in the multi-beam writing optical system of the present invention.

FIG. 4 is a diagram for explaining the light source unit shown in FIG.

5 is a diagram for explaining the inclination of the emission axis of each light source unit in the light source unit shown in FIG.

6A and 6B are views for explaining the positional relationship of the coupling lens corresponding to each semiconductor laser in the light source unit shown in FIG.

FIG. 7 is a diagram for explaining the adjustment of the scanning line pitch on the surface to be scanned in the embodiment shown in FIG.

FIG. 8 is a diagram for explaining the invention described in claim 5;

FIG. 9 is a diagram for explaining the invention described in claim 8;

FIG. 10 is a diagram for explaining a problem when the emission axis of each light source unit shifts in the sub-scanning direction after combination.

FIG. 11 is a diagram for explaining the invention according to claim 14;

FIG. 12 is a diagram for explaining a comparative example with respect to the inventions of claims 2 and 3.

FIG. 13 is a diagram for explaining the invention described in claim 1;

FIG. 14 is a diagram for explaining another form of the light source unit.

FIG. 15 shows 3 on the surface to be scanned in the case of 3-beam scanning.
It is a figure for explaining the state of a light spot.

[Explanation of symbols]

302 First imaging system 303 Deflector 304,308 Second imaging system 309 Photoreceptor that is the substance of the surface to be scanned

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-9-274152 (JP, A) JP-A-10-115789 (JP, A) JP-A-11-212006 (JP, A) JP-A-10- 3047 (JP, A) JP-A-9-218363 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 26/10

Claims (15)

(57) [Claims] 1. A multi-beam writing optical system for simultaneously scanning a plurality of scanning lines in a main scanning direction by a plurality of light beams separated in a sub-scanning direction on a surface to be scanned, the plurality of which can be individually modulated. Light emitting parts, a plurality of coupling optical systems provided corresponding to the respective light emitting parts, for taking in the light beams emitted from the corresponding light emitting parts, and a plurality of light beams coupled by these coupling optical systems as sub-devices. A first image forming system for forming an image in the scanning direction; a deflector for deflecting a plurality of light beams having a deflecting / reflecting surface in the vicinity of a light beam image forming position by the first optical system; Second for focusing the light beam on the surface to be scanned
Among the optical elements that form the second image forming system and that have the largest positive power in the sub scanning direction, the focal length in the sub scanning direction is f. beam, within the scope of ± f / 2 from the largest optical element of the sub-scanning direction with a positive power, intersects the sub-scanning direction, the light source unit to emit by combining the plurality of light beams, an odd number Paired with a semiconductor laser and each of the semiconductor lasers
An odd number of coupling lights provided to capture the light beam
First, the academic system and the semiconductor laser located in the center of the main scanning direction
Support unit that is placed on the injection axis of and supports them integrally
A first light source section having a material, an even number of semiconductor lasers, and each of these semiconductor lasers.
An even number of couplings provided in pairs to capture the light beam
Optics and these are symmetrical about the second emission axis in the main scanning direction
Having a support member that is arranged in a uniform manner and integrally supports the second member
Sub-scans the light beams from the light source unit and the first and second light source units.
Beam synthesizing means for emitting light in close proximity to each other in a direction, and the positions of the first and second light source units are symmetrical with respect to respective emission axes.
The light beam emitted from the semiconductor laser in the
It is designed to divergely enter the image system in the sub-scanning direction.
Multibeam write optical system, characterized in that made the. 2. A plurality of devices separated in the sub-scanning direction on the surface to be scanned.
Simultaneous scanning of multiple scan lines in the main scan direction by the light beam
In the multi-beam writing optical system, a plurality of light emitting parts that can be individually modulated and provided corresponding to each light emitting part are emitted from the corresponding light emitting parts.
Multiple coupling optics that capture the light beam to be emitted and the multiple coupling optics that are coupled by these coupling optics.
A first imaging system for imaging a number of light beams in the sub-scanning direction, and deflection reflection in the vicinity of the light beam imaging position by the first optical system
A deflector having a surface for deflecting a plurality of light beams and a second deflector for imaging the deflected light beams on a surface to be scanned.
An image forming system, and among the optical elements forming the second image forming system, the sub-scanning direction
Focal length of the optical element with the largest positive power in the sub-scanning direction
When the separation is f, the plurality of light beams are
Direction is ± f / 2 from the optical element with the largest positive power.
Inside the enclosure, a light source section that intersects in the sub-scanning direction and combines and emits the plurality of light beams is provided with an even number of semiconductor lasers and each of these semiconductor lasers.
Multiple coupling lights that are provided in pairs to capture light beams
The academic system and these are arranged symmetrically with respect to the first ejection axis in the main scanning direction.
A first light source unit having a support member that is lined up and integrally supported
And a second light source part similar to the first light source part, and sub-scans with the light beams from the first and second light source parts.
A light beam emitted from a semiconductor laser at a position symmetrical with respect to each emission axis of the first and second light source sections, the first image forming system having a beam combining means for emitting light in close proximity to each other. On the other hand, a multi-beam writing optical system characterized in that the multi-beam writing optical system is configured to divergely enter in the sub-scanning direction. 3. The multi-beam writing optical system according to claim 1 or 2 , wherein each chief ray of a plurality of light beams emitted from a plurality of light emitting units is
A multi-beam writing optical system, which divergently enters the first imaging system in the sub-scanning direction. 4. The multi-beam writing optical system according to claim 1, 2 or 3 , wherein each coupling optical system is a coupling lens, and the light emitting point positions of the semiconductor lasers of the first and second light source sections. Is set to be lower in the sub-scanning direction than the optical axis of the coupling lens with respect to the side where the optical axis of the coupling lens is above the first or second emission axis in the sub-scanning direction.
Regarding the side where the optical axis of the coupling lens is below the first or second emission axis in the sub-scanning direction, it should be set above the optical axis of the coupling lens in the sub-scanning direction. Characteristic multi-beam writing optical system. 5. The multi-beam writing optical system according to any one of claims 1 to 4 , wherein the action of each coupling optical system is a collimating action for making a light beam emitted from a semiconductor laser a parallel light beam. A multi-beam writing optical system characterized by the above. 6. The multi-beam writing optical system according to any one of claims 1 to 5, wherein the first and second light source sections and the beam combining means are substantially integrally modularized and held. Is provided to support the first and second light source units rotatably around a rotation reference matched with the reference optical axis of the optical system after the first imaging system, and to support the first and second light source units with respect to the base member. A multi-beam writing optical system characterized by being independently rotatable around an emission axis as a rotation center. 7. The multi-beam writing optical system according to any one of claims 1 to 6, wherein the emission axis of the first light source section and the emission axis of the second light source section are predetermined in the main scanning direction. A multi-beam writing optical system, wherein the first and second light source sections are arranged so as to form an angle or be separated by a predetermined distance. 8. The multi-beam writing optical system according to any one of claims 1 to 7, wherein the exit axis of the first light source section and the exit axis of the second light source section are the first imaging system. A multi-beam writing optical system, wherein the first and second light source units are arranged so as to be symmetrical in the main scanning direction with respect to a reference optical axis of the subsequent optical system. 9. A multi-beam writing optical system according to any one of claims 1 to 8, the first light source unit having a plurality of semiconductor lasers, a plurality of which are supported by the first light source The principal rays of the respective light beams emitted from the semiconductor laser intersect in the main scanning direction in the vicinity of the deflection reflection surface of the deflector, and the respective rays emitted from the plurality of semiconductor lasers supported by the second light source unit. Multi-beam writing, wherein each of the plurality of semiconductor lasers is set in the first and second light source units so that the chief ray of the beam intersects in the main scanning direction in the vicinity of the deflecting reflection surface. Optical system. 10. The multi-beam writing optical system according to claim 9 , wherein the semiconductor laser which is not on the emission axis of the light source section is set to be displaced from the optical axis of the corresponding coupling optical system in the main scanning direction. Is a multi-beam writing optical system. 11. The multi-beam writing optical system according to any one of claims 1 to 10, wherein the first emission axis and the second emission axis are in the main scanning direction in the vicinity of the deflection reflection surface of the optical deflector. The above first so as to intersect optically at
The first and second light source units are arranged such that the emission axis of the light source unit and the emission axis of the second light source unit form a predetermined angle in the main scanning direction or are separated by a predetermined distance in the main scanning direction. A multi-beam writing optical system characterized by the above. 12. The multi-beam writing optical system according to any one of claims 1 to 11 , wherein the first and second light source sections are provided with a semiconductor laser and a cup which are symmetrical with respect to respective emission axes. A multi-beam writing optical system, characterized in that, in a pair of ring optical systems, the amount of shift from the optical axis of the coupling optical system of the semiconductor laser is the same. 13. The multi-beam light source apparatus according to any one of claims 1 to 12, an injection axis of the injection axis and the second light source section of the first light source unit, the sub-scanning direction in the following beam combining means A multi-beam writing optical system characterized in that 14. A circle according to any one of claims 1 to 13.
The CHIBEAM writing optics scans the photoconductive photoreceptor.
A digital copying apparatus characterized by performing writing by writing. 15. A circle according to any one of claims 1 to 13.
The CHIBEAM writing optics scans the photoconductive photoreceptor.
A laser printer characterized by writing by writing.