JP2004020791A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform four-beam scanning by combining two units of two-beam light sources which are easily manufactured without preparing a four-beam light source that has difficulty of manufacture. <P>SOLUTION: In an optical scanner possessing an optical synthesizing means that is provided with two light source units holding two light sources to generate light and incorporating a means to convert the light generated by the light source into parallel light and synthesizes four light beams from two light sources units on nearly the same optical path, a light deflecting means to deflect four synthesized light beams and to perform scanning with them and an image formation means to form an image with four light beams which are deflected and by which the scanning is performed on a medium to be scanned, a mechanisms for adjusting the deflection angle of the light from the light source units in a scanning direction is provided at either one of light source units and such a mechanism for adjusting it in a subscanning direction is provided at the other light source unit. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical scanning device used for a laser printer or the like.
[0002]
[Prior art]
In order to perform high-speed printing and high dot density printing with a laser printer, it is necessary to increase the number of scans per unit time. The number of repetitive scanning lines can be increased to some extent by increasing the number of rotations of the light deflecting means or increasing the number of mirror surfaces, but there is a limit. Therefore, it is well known that a multiple beam scanning method for scanning a large number of lasers at once is effective. As an example of this, a plurality of individually modulatable semiconductor laser elements as disclosed in Japanese Patent Publication No. 60-33019 are arranged in an array, each emitted light is made parallel by a single collimator lens, and the light is deflected. There is a method of simultaneously scanning the scanning surface with a plurality of laser beams via the means and the Fθ lens.
[0003]
[Problems to be solved by the invention]
In the above-mentioned conventional method, when the number of beams is large, the manufacturing accuracy of the light source is required to be high, and there is a problem that the yield is lowered and the manufacturing cost is increased. In the multi-beam light source, the elements 1 are ideally arranged in a line as shown in FIG. 14, but as shown in FIG. 13, the vertical positional deviation corresponds to the deviation of the scanning line interval. Therefore, they need to be arranged with high precision. This is a problem because it cannot be corrected by adjustment or the like. For example, when the number of elements is 4 as shown in FIG. 16, the size of the element 1 is φ3 μm, and the element interval is 100 μm, the diameter of the spot 2 on the medium to be scanned is φ60 μm which is 20 times as large as shown in FIG. Thus, the spot interval becomes 2000 μm. At this time, when the inclination angle is 1.212 degrees, the scanning interval is 42.3 μm, which is equivalent to 600 dpi. If the permissible amount of the deviation of the scanning line interval is set to ± 4.23 μm of 10%, the positional accuracy in the element portion needs to be ± 0.21 μm, which is a value difficult to manufacture.
[0004]
[Means for Solving the Problems]
The present invention includes two light source units each including two light sources for generating light and including a unit for parallelizing the light generated from the light sources, and the four light beams from the two light source units are substantially the same. An optical scanning device comprising: a light combining unit that combines light on an optical path; a light deflecting unit that deflects and scans the combined four light beams; and an imaging unit that forms an image of the deflected and scanned four light beams on a medium to be scanned. In the apparatus, one of the two light source units is provided with a mechanism capable of adjusting a deflection angle of light from the light source unit in the scanning direction and the other light source unit in the sub-scanning direction. And
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an overall view of an embodiment of the present invention. The light source unit 5a, which includes a semiconductor laser 3a having two elements 1 and a collimator lens 4a for converting light into parallel light, is capable of rotational adjustment about the optical axis of the collimator lens 4a, and has an arrangement of light sources. Is mounted on a sub-scanning direction adjusting mechanism 15 which is a mechanism for rotating the axis about the direction of. Further, the light source unit 5b including the semiconductor laser 3b having two elements 1 and the collimator lens 4b for converting light into parallel light is capable of adjusting the rotation about the optical axis of the collimator lens 4b and scanning. It is mounted on a scanning direction adjusting mechanism 16 that rotates about a direction perpendicular to the plane as an axis. The light from the unit 5 b passes through the λ / 2 plate 6 and changes the polarization direction, thereby increasing the reflectance at the polarizing prism 7. The light combined by the polarizing prism 7 as the combining means passes through the λ / 4 plate 8 and is changed from linearly polarized light to circularly polarized light. The difference in reflectance due to the difference and the difference in transmittance for each scanning angle of the Fθ lens are suppressed. The above components are arranged on the base 9. The base 9 is mounted on an overall rotation adjusting mechanism 17 capable of adjusting rotation about the optical axes of the cylindrical lenses 10 and 11. The four lights emitted from the base 9 pass through the cylindrical lenses 10 and 11 and are deflected by the light deflecting means 12, pass through the Fθ lens 13 which is an image forming means, and form four spots 2a and 2b on the medium 14 to be scanned. Scan above. The above is the schematic configuration.
[0006]
The details of each component and the adjustment method will be described below with reference to the drawings. FIG. 2 shows a mechanism for adjusting the rotation of the collimator lenses 4a and 4b about the optical axis. This is provided in light source units 5a and 5b including semiconductor lasers 3a and 3b having two elements 1 and collimator lenses 4a and 4b. The unit 5a or 5b is mounted on the holding base 21, and a gear 26 is formed on the unit 5a or 5b. The gear 26 moves slightly as the gear 25 rotates. The gear 25 is directly connected to the adjustment knob 22 and is fixed by two supports 23. The two supports 23 are fixed to the holding base 21 by four fixing screws 24. Reference numeral 41 in FIG. 2 denotes a light emission port. The adjustment knob 22, the support 23, and the fixing screw 24 may be removed after the adjustment and fixing. This adjustment corrects that the spot 2a from 5a is inclined α with respect to the scanning direction on the medium 14 to be scanned, as shown in FIG. 3, and the spot 2b from 5b is inclined β with respect to the scanning direction, as shown in FIG. As shown in the above, α = β = 0 degrees with respect to the scanning direction.
[0007]
Next, the scanning direction adjusting mechanism 16 below the light source unit 5b will be described. A detailed view is shown in FIG. In this adjustment, as shown in FIG. 6, the distance A between the spot 2a from the unit 5a and the spot 2b from the unit 5b is adjusted. The light source unit 5b and the holding base 21 set 27 are fixed on a scanning direction holding base 29, held so as to be rotatable around a pin 28, and provided with a gear 26. By rotating the adjustment knob 22 of the adjustment mechanism, the gear 25 is rotated, and the gear 26 can be finely moved. The distance A shown in FIG. 6 may be adjusted to be the same as the distance B between 2a and 2b. FIG. 7 shows the state after the adjustment. Note that reference numeral 41 in FIG. 5 denotes a light emission port.
[0008]
Other examples of the scanning direction adjusting means will be described below. As shown in FIGS. 17 and 18, the semiconductor laser 3 is fixed to the semiconductor laser holder 50 with the screws 24. The collimator lens 4 is fixed to the collimator lens holder 51 with an adhesive or the like. The semiconductor laser holder 50 has a long hole 52 that is long in the scanning direction. The hole is integrated with the collimator lens holder 51 through the screw 24. At this time, the inclination of the light beam in the scanning direction can be adjusted by adjusting the position of the screw 24 passing through the elongated hole 52. In the examples of FIGS. 17 and 18, the elongated hole is located on the side of the semiconductor laser holder 50, but the elongated hole is located on the side of the collimator lens holder 51, and the scanning direction of the light beam is adjusted by adjusting the position of the collimator lens 4 in the scanning direction. Adjustments are also possible.
[0009]
Next, the sub-scanning direction adjusting mechanism 15 below the light source unit 5a will be described. A detailed view is shown in FIG. In this adjustment, as shown in FIG. 9, the distance C in the sub-scanning direction between the spot 2a from the unit 5a and the spot 2b from the unit 5b is adjusted. The light source unit 5a and the holding base 21 set 30 are fixed on a sub-scanning direction holding base 32, and the sub-scanning direction holding base 32 is held by two supports 23 so as to be rotatable about an axis 31 as a center axis. Have been. In addition, a screw hole is provided at the end opposite to the shaft, and by rotating the adjustment knob 22, the sub-scanning direction holding base 32 is inclined. This value may be adjusted so that the distance C shown in FIG. FIG. 10 shows the state after the adjustment.
[0010]
Other examples of the sub-scanning direction adjusting means will be described below. As shown in FIGS. 19 and 20, the semiconductor laser 3 is fixed to the semiconductor laser holder 50 with the screws 24. The collimator lens 4 is fixed to the collimator lens holder 51 with an adhesive or the like. The semiconductor laser holder 50 has a long hole 52 long in the sub-scanning direction, and the screw 24 is inserted into this hole to be integrated with the collimator lens holder 51. At this time, the inclination of the light beam in the sub-scanning direction can be adjusted by adjusting the position of the screw 24 passing through the elongated hole 52. 19 and 20, the elongated hole is on the side of the semiconductor laser holder 50. Conversely, the elongated hole is on the side of the collimator lens holder 51, and by adjusting the position of the collimator lens 4 in the scanning direction, the sub-scanning of the light beam is performed. Direction adjustment is also possible.
[0011]
Finally, the overall rotation adjusting mechanism 17 will be described. A detailed view is shown in FIG. In this adjustment, the spots 2a and 2b arranged in a line as shown in FIG. 10 are inclined at an angle θ as shown in FIG. 12, and the scanning interval is adjusted to a predetermined value. For example, at 600 dpi, the scanning interval is 42.3 μm. The base 9 is fixed to the whole holding base 40, and a gear 26 is provided around the whole holding base 40, and the rotation of the whole holding base 40 can be adjusted by the gear 25 around the center of the emission port 41. The gear 25 is rotatable by an adjustment knob 22, which is fixed by a support 23, and the support 23 is fixed to the main body of the overall rotation adjustment mechanism 17 by a fixing screw 24.
[0012]
In addition, if the adjusting mechanism is attached to the main body, the manufacturing price increases, so that the adjusting mechanism may be made removable after the adjusting and fixing. In this case, the light source unit 5a is provided with the sub-scanning direction adjusting mechanism 15, and the light source unit 5b is provided with the scanning direction adjusting mechanism 16, but may be reversed.
[0013]
Here, the gist of the present invention will be described again. When the combining method as shown in FIG. 1 is used, the adjustment of A (scanning direction interval) shown in FIG. 6 and C (sub-scanning direction interval) shown in FIG. 9 directly affects print quality such as pitch unevenness, and is therefore important. is there. Examples of this adjustment mechanism are shown in FIGS. 5 and 8, respectively. These two adjustment mechanisms need not be attached to both the unit 5a and the unit 5b, but may be provided only for one unit, for example, only the unit 5a as shown in FIG. 6A and 9C can be sufficiently adjusted with reference to the light spot from the unit 5b. The above is the first essential point of the present invention.
[0014]
When the adjustment mechanism is concentrated on one unit as shown in FIG. 21, there are problems in that the structure becomes complicated and adjustment is difficult, and it takes time because there are a plurality of adjustment points. Therefore, as shown in FIG. 1, by disposing the adjusting mechanism in two units, the structure is simplified and the adjustment is facilitated. The above is the second essential point of the present invention.
[0015]
【The invention's effect】
As described above, according to the present invention, it is possible to perform four-beam scanning by combining two easily manufactured light sources without creating a four-beam light source that is difficult to manufacture.
[Brief description of the drawings]
FIG. 1 is an overall view of an optical scanning device according to the present invention.
FIG. 2 is a diagram showing a rotation adjusting mechanism.
FIG. 3 is a diagram illustrating a state of a spot on a scanned medium.
FIG. 4 is a diagram illustrating a state of a spot on a medium to be scanned.
FIG. 5 is a diagram illustrating a scanning direction adjustment mechanism.
FIG. 6 is a diagram showing a state of a spot on a medium to be scanned.
FIG. 7 is a diagram illustrating a state of a spot on a medium to be scanned.
FIG. 8 is a diagram illustrating a sub-scanning direction adjusting mechanism.
FIG. 9 is a diagram illustrating a state of a spot on a medium to be scanned.
FIG. 10 is a diagram illustrating a state of a spot on a medium to be scanned.
FIG. 11 is a view showing an overall rotation adjusting mechanism.
FIG. 12 is a diagram illustrating a state of a spot on a medium to be scanned.
FIG. 13 is a diagram showing an arrangement of elements.
FIG. 14 is a diagram showing an arrangement of elements.
FIG. 15 is a diagram showing a state of a spot on a medium to be scanned.
FIG. 16 is a diagram showing an arrangement of elements.
FIG. 17 is a diagram illustrating an example of a scanning direction adjustment mechanism.
FIG. 18 is a diagram illustrating an example of a scanning direction adjustment mechanism.
FIG. 19 is a diagram illustrating an example of a sub-scanning direction adjusting mechanism.
FIG. 20 is a diagram illustrating an example of a sub-scanning direction adjustment mechanism.
FIG. 21 is an overall view of an optical scanning device having three adjustment mechanisms on one side and one on the other side.
[Explanation of symbols]
1 Element 2, 2a, 2b Spot 3, 3a, 3b Semiconductor laser 4, 4a, 4b Collimator lens 5a, 5b Light source unit 6 λ / 2 plate 7 Polarizing prism 8 λ / 4 plate 9 Base 10 Cylindrical lens 11 Lens 12 Optical deflection Means 13 Fθ lens 14 Scanned medium 15 Sub-scanning direction adjusting mechanism 16 Scanning direction adjusting mechanism 17 Overall rotation adjusting mechanism 21 Holding base 22 Adjusting knob 23 Supporter 24 Fixing screws 25, 26 Gear 27 Light source unit and holding base set 28 Pin 29 Scanning direction holding base 30 Light source unit and holding base set 31 Axis 32 Sub-scanning direction holding base 40 Overall holding base 41 Emission port 50 Semiconductor laser holder 51 Collimator lens holder 52 Slot

Claims (1)

Two sets of light source units including means for holding two light sources for generating light and converting the light generated from the light sources into parallel light are provided, and the four lights from the two light source units are combined on substantially the same optical path. An optical scanning device, comprising: a light synthesizing unit configured to deflect and scan the combined four light beams; and an imaging unit configured to image the four deflection-scanned light beams on a medium to be scanned. An optical scanning device comprising: a mechanism for adjusting a deflection angle of light from the light source unit in one of the two light source units in the scanning direction and in the other light source unit in the sub-scanning direction. apparatus.

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