JP3463054B2 - Multi-beam scanner - 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 scanning device, and more particularly to a multi-beam scanning device used for exposing a photosensitive material by simultaneously focusing a plurality of light beams on a predetermined photosensitive material.

[0002]

2. Description of the Related Art As a multi-beam scanning device of this type,
For example, a technique described in Japanese Patent Application Laid-Open No. 5-276335 (conventional example 1) or a technique described in Japanese Patent Application Laid-Open No. 4-101112 (conventional example 2) is known.

In the conventional example 1, in an inner drum scanning type scanning device, one of the laser beams output from two laser diodes is passed through a wedge prism to be deflected and then rotated. A configuration is disclosed in which one laser beam is deflected by an optical deflector that rotates in synchronism with the wedge prism, and rotational scanning is performed on a recording sheet held on the inner peripheral surface of the drum.

Further, in the second conventional example, a light beam emitted from a light source having a plurality of light emitting portions is guided to an optical deflector by an optical means, and the deflected light beam is crystallized by a crystal optical system on a surface to be scanned. In a multi-beam scanning optical system that simultaneously scans with a plurality of light beams, the plurality of light emitting units are arranged in a direction orthogonal to the scanning direction of the light beams, and the optical means or the imaging optical system uses a plurality of light beams. A configuration is disclosed in which an adjusting member that adjusts a scanning interval of scanning lines on a line to be scanned is provided. As the adjusting member, one having a negative lens and a positive lens is used. Then, the imaging distance in the sub-scanning direction is made variable by changing the focal point position by relatively changing the lens interval, thereby adjusting the scanning interval to a desired position.

[0005]

However, in the case of the apparatus of Conventional Example 1, this type of adjustment is difficult because the pitch adjustment between the laser beams is determined by the apex angle of the wedge prism. When adjusting the pitch during assembly, it is necessary to adjust the mounting position of the laser diode, and it is difficult to obtain a desired scanning interval. Also,
Since the pitch of the laser beam is substantially determined only by the apex angle of the wedge prism, for example, there is a switch between high density and low density, and it is difficult to deal with the case where the pitch of the laser beam needs to be greatly changed. Become.

Further, in the inner drum scanning recording apparatus as in the prior art example 1, the motor rotates at high speed, and
Accurate rotation unevenness is also required. However, in the case of the configuration of the first conventional example, a gear mechanism is provided for performing the synchronous rotation as described above, and an inertial laser beam scanning unit such as a wedge prism or an optical deflector is attached to the gear mechanism. Therefore, it is difficult to realize high speed rotation and high accuracy.

On the other hand, in the case of the apparatus of the conventional example 2, since the positive lens and the negative lens which are the adjusting members are moved to adjust the image forming magnification in the sub-scanning direction, it takes time for feedback at the time of adjustment. . Further, since the beam diameter in the sub-scanning direction on the image forming surface is changed by adjusting the imaging magnification in the sub-scanning direction, it is not suitable for high-definition and high-density recording.

Further, a semiconductor laser array having a plurality of laser diodes is usually used as the plurality of light emitting portions as described above, and the pitch interval in the semiconductor laser array is actually about 50 to 150 μm. When an array of semiconductor lasers is used in this configuration, crosstalk occurs due to the effect of heat generation, and it is difficult to drive the laser diodes independently. In addition, since the plurality of light emitting units are arranged in the direction orthogonal to the scanning direction of the light beam, an optical element for correcting the divergence angle with respect to the scanning direction is required, and the structure becomes complicated.

An object of the present invention is to eliminate the above-mentioned problems, to easily adjust the pitch interval between light beams, and to easily adjust the scanning interval of a plurality of light beams.
It is to provide a multi-beam scanning device.

[0010]

A multi-beam scanning device provided by the present invention comprises a plurality of light emitting means for respectively outputting light beams, and a combining means for aligning the optical axes of the plurality of light beams having different traveling directions. A deflection means for deflecting the plurality of light beams whose optical axes are aligned, and an image forming means for forming an image of the plurality of deflected light beams on a surface to be scanned,
Further, an angular displacement adjusting unit is provided which is provided between the light emitting means and the synthesizing means and which deflects at least one of the plurality of light beams in a sub-scanning direction orthogonal to the scanning direction. .

In the above construction, the angular displacement adjusting unit is constructed by combining, for example, two wedge prisms, and the position where the light beam goes straight is the origin.
Then, these two wedge prisms have the same angle in opposite directions.
By rotating in degrees, the degree of deflection is adjusted. The combining means is, for example, a deflecting beam splitter, and in this case, λ for changing the polarization direction of one of the light beams incident on the deflecting beam splitter.
It can be configured to have a / 2 plate. Such λ
By providing the / 2 plate, the polarization direction of the light beam can be changed according to the deflection beam splitter, and the transmittance or the reflectance of the light beam in the polarization beam splitter can be increased to eliminate the loss of the light amount.

In a preferred embodiment, semiconductor lasers each having a collimator lens are used as the plurality of light emitting means. Further, a plurality of laser beams are combined by aligning the optical axes of the laser beams from these semiconductor lasers using the deflecting beam splitter as described above. These laser beams are then focused on the image forming plane by a predetermined image forming optical system.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A multi-beam scanning device according to an embodiment of the present invention will be described below. FIG. 1 is an explanatory diagram showing an outline of an optical system in the embodiment. This multi-beam scanning device includes two laser diodes LD1 and LD2 as light emitting means (light sources), collimator lenses 7 and 8,
The λ / 2 plate 5, the polarization beam splitter 6, the angular displacement unit 14, the cylindrical lenses 10 and 11, the polygon mirror 9, the fθ lens 11 and the like.

The light beams from the laser diodes LD1 and LD2 are collimated by the collimator lenses 7 and 8, respectively. Here, the light beam 3 from the laser diode LD1 is, as shown in FIG.
The light beam is incident on the second plate 5, the polarization direction is changed by 90 ° by the λ / 2 plate 5, and the S-wave is emitted.
Is incident on. Further, the light beam 4 from the laser diode LD2 enters the λ / 2 plate 5 as a P wave.

The deflecting beam splitter 6 transmits the S wave,
The P wave is made to reflect. Therefore, the light beam 3 from the laser diode LD1 passes through the deflection beam splitter 6. Specifically, the transmittance in this case is, for example, 90% or more. The light beam 3 then passes through the cylindrical lens 10 and is focused in the sub-scanning direction by the polygon mirror 9 used as an optical deflector.

The cylindrical lens 10 is arranged for correcting the surface tilt of the polygon mirror 9, for adjusting the astigmatic difference between the laser diodes LD1 and LD2, and for correcting the divergence angle, and has a refracting power in the sub-scanning direction. .
The polygon mirror 9 is a deflector for deflecting in the main scanning direction.

The light beam 3 is reflected by the polygon mirror 9
Through the fθ lens 11 that linearly deflects the deflection angle on the image plane during planar scanning, and further passes through the cylindrical lens 12 for tilt correction on the image plane,
An image is formed on the scanning material surface 13 of the photosensitive material P. The photosensitive material P
For example, OPC (Organic Photo)
An organic photoconductor) plate is used.

On the other hand, the beam 4 emitted from the laser diode LD2 becomes a parallel light beam by the collimator lens 8, and then passes through the angular displacement adjusting unit 14, and is deviated from the minute angle optical axis. It is incident as a P wave on the incident surface of No. The deflecting beam splitter 6 is
The light beam 4 is reflected by its reflection surface. In this case, the reflectance is specifically 90% or more. After that, the light beam 4 passes through the same optical path as that of the light beam 3, that is, passes through the cylindrical lens 10 and is reflected by the surface of the polygon mirror 9, and then passes through the fθ lens 11 and the cylindrical lens 12 to give a scanning feeling. An image is formed on the material surface 13.

As described above, the laser diode LD1,
By providing the beam splitter 6 as a means for synthesizing the two light beams from the LD 2, it is possible to reduce the loss of the emitted light amount when using a half mirror to 50% or more, to 10% or less. Becomes As a result, it becomes possible to secure a large power margin between the laser diodes LD1 and LD2.

The angular displacement adjusting unit 14 is shown in FIG.
With reference to FIG. 4, the Cairo prism 15 is formed by combining two wedge prisms 16. Then, in order to cancel out the declination of each other, with the position where the light beams travel straight as the origin, the two wedge prisms 16 can be rotated in the opposite directions at the same angle. A specific configuration example for this purpose is shown in FIG.

With such a structure, the deflection of the light beam in the sub-scanning direction can be adjusted, and the light beam can be deflected in the sub-scanning direction. That is, for example, as shown in FIG. 6, the imaging by the light beam from the laser diode LD2 can be adjusted in the sub-scanning direction M with respect to the imaging by the light beam from the laser diode LD1 on the imaging plane. It will be possible. Note that FIG.
6A shows before adjustment, and FIG. 6B shows after adjustment.

3 and 4, θ is the deviation angle of one wedge prism 16, φ is the rotation angle of the wedge prism 16 (the same angle in opposite directions in the two wedge prisms 16), and δ is the Cairo prism 15. And the declination of

[Expression 1] δ = tan ⁻¹ (2 · tan θ · sin φ) (1)

Further, between the apex angle α and the deviation angle θ in the wedge prism 16,

## EQU2 ## There is a relationship of θ = (n-1) α (2). Here, n is the refractive index and α is the apex angle of the wedge prism.

From the above equations (1) and (2), the deflection adjustment capability of the Cairo prism 15 is determined by the wedge prism 16
When the apex angle α of is 0.5 ° and n in the deviation angle θ of the wedge prism 16 is 1.5, it is 0.25 °. Therefore, if the deviation angle θ of one of the wedge prisms 15 is 0.25 °, it can be understood from the equation (1) that the deviation angle is only 0.08 ° even if it is rotated by 10 °. Also, it can be seen that even if it is rotated by 90 °, it can be moved with a declination of 0.5 °. Therefore, it is understood that the use of such a Cairo prism 15 is an effective means for adjusting a minute angle.

Next, the specific structure of the angular displacement adjusting unit 14 will be described with reference to FIG. Each of the two wedge prisms 16 is mounted on a holder 18 in which a rack gear 17 is processed. Note that, in FIG. 5, the holder on which the wedge prism 16 on the back side is mounted is omitted for convenience of illustration. A pinion gear 19 is vertically attached between the two wedge prisms 16, and each rack gear 1
It works together with 7. Further, the pinion gear 19 is connected to a gear 21 that is interlocked with the adjusting knob 20. As shown in FIG. 5, this angular displacement unit 14
Are arranged so that the Cairo prism 15 has a deviation angle about the optical axis.

In the angular displacement adjusting unit 14 having such a structure, by rotating the adjusting knob 20, the two wedge prisms 16 can be rotated at the same angle in the opposite directions as described above. Also, the gear 21 and the pinion gear 19
By increasing the speed reduction ratio of, the angular displacement can be adjusted more easily. For example, when the declination is 0.08 °, it is sufficient to rotate the Cairo prism 15 by 10 °. Therefore, when the reduction ratio is 1/8, the adjustment knob 20 can be rotated by 80 °. Good.

As described above, in the multi-beam scanning device of this embodiment, the adjusting knob 2 of the angular displacement adjusting unit 14 is used.
By rotating 0, the interval (scan interval) between the scanning lines formed by the laser diodes LD1 and LD2 on the photosensitive material P
Can be adjusted.

By the way, usually, in this kind of optical system, in order to have a density of 400 to 1000 dpi and to obtain a multi-beam on the image plane, the angular displacement adjusting unit 14 is used to form 0.008 ° to 0 °. It suffices if the deflection angle can be adjusted by about 0.08 °. Further, the adjustment of the start position in the main scanning direction can be performed by mounting the phase start sensor 22 on the image plane as shown in FIG. Then, with this phase start sensor 22, the laser diode LD
By shifting the start point in the main scanning direction by the difference between the scanning times of 1 and LD2, the laser diodes LD1 and L
The scanning start position by D2 can be adjusted.

Although the λ / 2 plate is provided between the collimator lens 7 and the deflecting beam splitter in the above description, it may be provided between the angular displacement unit and the deflecting beam splitter.

[0030]

As is apparent from the above description, according to the multi-beam scanning device of the present invention, the pitch interval between the light beams can be easily adjusted, and the scanning intervals of the plurality of light beams can be easily adjusted. Can be adjusted to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a multi-beam scanning device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a beam splitter which constitutes the multi-beam scanning device of FIG.

FIG. 3 is an explanatory view of a Cairo prism which constitutes an angular displacement adjusting unit of the multi-beam scanning device of FIG.

FIG. 4 is an explanatory diagram of a deviation angle of a wedge prism that constitutes a Cairo prism.

FIG. 5 is an explanatory view of an angular displacement adjustment unit.

6A is an explanatory diagram showing a spot position of a light beam before adjustment on an image forming plane, and FIG. 6B is an explanatory diagram showing a spot position of the same after adjustment.

[Explanation of symbols]

5 λ / 2 6 Deflection beam splitter 7,8 Collimator lens 9 polygon mirror 14 Angular displacement unit

Claims (2)

(57) [Claims] 1. A plurality of light emitting means for respectively outputting light beams, a synthesizing means for aligning the optical axes of the plurality of light beams having different traveling directions, and a deflection for deflecting the plurality of light axes aligned with each other. Means and image forming means for forming an image of the deflected light beams on a surface to be scanned, and further provided between the light emitting means and the combining means, An angular displacement adjusting unit for deflecting at least one in a sub-scanning direction orthogonal to the scanning direction is provided, and the angular displacement adjusting unit includes two wedge prisms.
The light beam goes straight ahead.
The origin of the position is the two wedge prisms.
Rotation at the same angle in the opposite direction, the degree of deflection
The multi-beam scanning device is characterized in that 2. The synthesizing means is a deflecting beam splitter, and further has a λ / 2 plate for changing the polarization direction of one of the light beams incident on the deflecting beam splitter. The described multi-beam scanning device.