JP3534791B2 - Beam scanning device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam scanning device used in a laser printer or the like, and more particularly to a beam scanning device for scanning a plurality of beams on an image carrier.

[0002]

2. Description of the Related Art Conventionally, an optical scanning device for forming a latent image on a photosensitive drum or other image carrier while optically scanning a modulated beam corresponding to image information has been known. This type of device is a laser printer. It is used as an exposure device for forming a latent image by being incorporated in an electrophotographic device such as the above. On the other hand, in recent years, in recording devices such as laser printers, the printing speed per sheet has been increased and increased.
In order to realize higher resolution, it is necessary to increase the scanning speed of the optical scanning device, but in order to achieve such high speed, a deflector such as a polygon mirror incorporated in the scanning device must be operated at high speed. Need to rotate.

However, for example, in the case of a printer of which the number of printing sheets of A4 size recording paper is about 18 sheets / min and 600 DPI, the rotation number of the polygon mirror is required to be 25000 RPM or more, while the polygon mirror is pivotally supported. 1,500 axial or radial bearings
Since the limit is around 0 RPM, it is necessary to use air bearings, oil bearings, etc. that can withstand the rotation of 25,000 RPM.
It is not preferable because it doubles.

For this reason, a multi-beam optical scanning system which simultaneously deflects a plurality of beams has been attracting attention as a means for increasing the scanning speed without increasing the rotation speed of the deflector. As this type of device, a semiconductor laser array in which a plurality of semiconductor lasers are arranged in one line in the sub-scanning direction is used, and a plurality of beams emitted from individual semiconductor lasers are arranged in the sub-scanning direction via a deflection mirror. Although there is a device in which beam scanning is performed in a uniform manner, high-precision beam scanning cannot be performed without any mechanism for adjusting the beam interval in the sub-scanning direction or the main scanning direction.

As such an adjusting mechanism, there has been proposed an apparatus in which a prism is arranged after the lens system for making the plurality of beams parallel to each other and the beam interval in the sub-scanning direction on the image carrier can be adjusted. (JP-A-62-226117)

[0006]

However, according to the above-mentioned prior art, since the prism is arranged on the parallel optical path of the two beams, the adjustment direction is only the sub-scanning direction, and the main scanning direction. Cannot be adjusted. That is, in the main scanning direction, an adjustment mechanism for adjusting the timing between the two beams is required in order to synchronize the writing positions of the two beams, but a prism is arranged on the parallel optical path of the two beams. But that adjustment is difficult.

Therefore, conventionally, a beam detecting means is provided at each writing start position of the beam to be scanned, and the beam transmitting timing on the beam oscillator side is synchronized based on the detection signal of the detecting means. In particular, in the case of using 3 to 4 beams as in a color digital copying machine, it is necessary to provide 3 to 4 beam detecting means and a circuit for adjusting the timing, as a result. The circuit configuration becomes complicated. The present invention has been made in view of the above-described conventional art, and an object of the present invention is to provide a beam scanning device capable of simply and easily adjusting the beam interval in the sub-scanning direction and adjusting the beam writing timing in the main scanning direction with a single member. To do.

[0008]

SUMMARY OF THE INVENTION The present invention is directed to illuminating from a light source.
Bee that collects multiple beams and guides them to a polygon mirror.
Beam from the polygon mirror
In the beam scanning device which scans the image carrier according to the above , the plurality of beams are provided on the upstream side of the beam split.
Of the other beams except the predetermined reference beam
A beam adjustment that adjusts the deviation of the beam on the beam optical path.
A beam adjusting mechanism is disposed on the entrance surface and the entrance surface.
Has an exit surface parallel to the projection surface and is incident on the entrance surface.
A transparent plate that transmits the emitted beam and sends it out from the emission surface,
The translucent plate is rotated in the main scanning direction to face the reference beam.
First rotating hand that adjusts the deviation of the writing start timing
Step and the translucent plate in the sub-scanning direction to rotate the reference beam.
Second pivoting hand for adjusting the deviation of the beam interval with respect to the beam
It is characterized by having a step . For example, in the present invention,
A substrate that is rotatable along the main scanning direction, and
Attached the translucent plate to the substrate on the optical path emission side
And a support plate that is tilted to and supported by the first rotation means.
Rotates the substrate along the main scanning direction to
A cam member for rotating the translucent plate in the main scanning direction,
The second rotation means is an angle formed by the support plate and the substrate.
Adjustment to rotate the translucent plate in the sub-scanning direction.
Equipped with adjusting screws.

[0009]

The present invention will be described step by step. As shown in FIG. 1, for example, in the case of a plate glass having an entrance surface and an exit surface parallel to each other, the following relationship holds for the relationship of the refractive index of the beam, so that the transmission angles θ and θ ″ of the incident light and the exit light are Will be equal. nsin θ = n ′ sin θ ′ n ′ sin θ ′ = nsi
nθ '' ∴ nsinθ = nsinθ ' ' ∴θ =
θ ″ n, n ′: Refractive index θ: Incident angle θ ′: Refraction angle with respect to the normal line of incident light θ ″: Exit angle Therefore, as is clear from the above description, the incident angle of the beam light passing through the plate glass When the flat glass is arranged so as to be inclined by θ, a deviation of Δx is generated with respect to the incident light. By utilizing this principle, by rotating the flat glass in a predetermined direction, the spot position on the beam emission side can be adjusted to an arbitrary spot position while maintaining a parallel relationship with the incident light.

Therefore, by rotating the flat glass in the main / sub-scanning direction, for example, the deviation of the beam interval with respect to the reference beam in the sub-scanning direction or the deviation of the writing timing with respect to the reference beam in the main-scanning direction is adjusted. And so on.

Therefore, according to the present invention, it is not necessary to dispose the beam detecting means for each of the plurality of beams, the beam detecting means may be disposed only for the reference beam, and only one beam detecting means is required. , No need for complicated detection circuit. The beam spot position can be adjusted, for example, at the manufacturing stage by picking it up with a beam scanning device and enlarging and projecting it on the display to match the specified position.Beam adjustment is performed only in the sub-scanning direction, and in the main scanning direction, the reference beam It is also possible to measure only the deviation with respect to, the data is bar-coded, and only the timing of video output is corrected by software based on the bar-code data.

Therefore, in this case, the flat glass can be rotated only in the sub-scanning direction. Here, the value of Δx can be expressed by the following equation. Δx = sin (θ−θ ′) / cos θ ′ × t (t is the thickness of the plate glass) 1) Since the relation of the formula 1) always holds, Δx increases as t increases.
Also increases, and Δt decreases as t decreases. Therefore, the flat glass is only required to be able to maintain the linear relationship between the rotation angle θ and the deviation Δx. When it is desired to increase Δx with respect to θ, the thickness of the flat glass may be increased, and the thickness of the flat glass may be decreased. Therefore, Δx can be reduced.

[0013]

Embodiments of the present invention will now be illustratively described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative positions and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely examples, unless otherwise specified. Not too much. Figure 2
3A and 3B are a front view and a plan view showing the configuration of a laser printer according to an embodiment of the present invention. 1A is a reference beam A, 1B is a respective semiconductor laser that oscillates an adjustment beam B, 2A, and 2A.
B is a collimator lens for collimating the respective beams, 3
A and 3B are cylindrical lenses for condensing on the polygon mirror 4, 3 is a beam split for collecting the respective beams and guiding them to the polygon mirror 4, 5 and 6 are Fθ lenses, and the polygon mirror 4 performs optical scanning in the main scanning direction. The formed beam is configured to be imaged on the generatrix of the photoconductor drum 7. The semiconductor laser 1A for sending out the reference beam and the semiconductor laser 1B for sending out the adjusting beam are arranged by being displaced by 90 ° in the main scanning direction, while the beam split 3 is arranged at the intersection of 45 °. Arranged as if the split surface were located. Denoted at 8 is a deflecting mirror for detecting the beam writing position, and denoted at 9 is its light receiving sensor. Since such a configuration is publicly known, detailed description thereof will be omitted.

In this embodiment, the beam adjustment consisting of the flat glass plate 10 is arranged on the optical path while the light beam after passing through the cylindrical lens 2B on the semiconductor laser 1B side for transmitting the adjustment beam B is guided to the beam split 3. Mechanism 20
To arrange. As shown in FIG. 4, the beam adjusting mechanism 20 includes the flat glass plate 10 and a rotating mechanism 20A for rotating the flat glass plate 10 in the main scanning direction and the sub scanning direction.

These will be described in detail below. The flat glass plate 10 is made of lens glass or quartz glass having a high laser beam transparency, and its entrance surface and exit surface are highly accurately polished into parallel surfaces. Here, the flat glass plate 10 does not have to have high precision and may be a normal flat glass. Recently, resin materials such as polycarbonate , which are also used for plastic lenses, can be used as long as the accuracy of parallel planes is obtained. The adjusting mechanism 20 includes a cam 21.
Is rotated about a shaft fulcrum 23 fitted into the bottom surface 22 of the main body along the bottom surface 22 of the main body, in other words, a predetermined angle along the main scanning direction, through a slot 25 and a screw shaft 26. Support plate 27 fixed on substrate 24
And a side portion of the support plate 27 is erected, and a tip side thereof is extended to the side wall 28 of the main body to form a leaf spring 29 pressed against the side wall 28 in a curved state. Stand up slightly tilted from the vertical toward the exit side of the optical path,
An L-shaped glass mounting plate 30 is fixed to the rising portion 27a. As a result, the mounting plate 30 is mounted at a slight inclination to the emitting side, and the flat glass plate 10 is mounted in the rectangular opening 30a of the standing surface of the mounting plate 30 and is located below the mounting part of the glass plate 10. The inclined surface 31 is formed so as to be inclined toward the
An adjusting screw 32 is screwed toward the 4 side, and the mounting plate 30 can be tilted in the sub-scanning direction by the advancing / retreating operation of the adjusting screw 32. Reference numeral 35 is a pressing spring for pressing and supporting the flat glass plate 10.

According to such an embodiment, by rotating the cam 21, the flat glass plate 10 is main-scanned through the substrate 24 by the biasing force of the leaf spring 29 or against the biasing force of the leaf spring 29. Adjustment screw 32
The mounting plate can be tilted in the sub-scanning direction by the forward / backward movement. Therefore, the beam spot position is adjusted, for example, at the manufacturing stage by picking up with a beam scanning device and enlarging and projecting it on the display while rotating the flat glass plate 10 in the main scanning direction by the rotation of the cam 21 and by moving the adjusting screw 32 forward and backward. By rotating the mounting plate in the sub-scanning direction, the mounting plate can be adjusted to the specified position.

[0017]

As described above, according to the present invention, the beam spacing in the sub-scanning direction and the beam in the main scanning direction can be adjusted by simply rotating the flat glass plate arranged on the parallel optical path of one beam in the predetermined scanning direction. You can easily and easily adjust the writing timing of. It has various remarkable effects.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the principle of the present invention.

FIG. 2 is a front view showing a configuration of a laser printer according to an embodiment of the present invention and an explanatory view showing a principle of rotation of a flat glass.

FIG. 3 is a plan view of FIG.

4A and 4B show a rotation adjusting mechanism of a flat glass, FIG. 4A is a plan view thereof, FIG. 4B is a front view, and FIG. 4C is a left side view.

[Explanation of symbols]

1A reference beam 1B adjusted beam 10 Flat glass plate (transparent plate)

Claims (2)

(57) [Claims] 1. A set of a plurality of beams emitted from a light source
Equipped with a beam split that leads to a polygon mirror
On the image carrier according to the beam from the polygon mirror
In a beam scanning device that scans a plurality of beams.
A beam other than the predetermined reference beam
Beam adjusting mechanism for adjusting the deviation of the beam on the optical path
Is arranged, and the beam adjusting mechanism is arranged on the incident surface and the incident surface.
A beam incident on the incident surface having an emission surface parallel to it.
A light-transmitting plate that transmits the light through the light-emitting surface, and the light-transmitting plate.
Rotate the plate in the main scanning direction to write on the reference beam.
First rotating means for adjusting the deviation of the start timing;
Rotate the translucent plate in the sub-scanning direction so that it becomes the reference beam.
Second rotating means for adjusting the deviation of the beam interval with respect to
A beam scanning device having . 2.Substrate that is rotatable in the main scanning direction
And attached to the substrate to transmit the light to the substrate.
And a support plate that supports the plate by inclining it toward the optical path emission side, The first rotating means moves the substrate along the main scanning direction.
To rotate the transparent plate in the main scanning direction.
Equipped with a cam member, The second rotation means is an angle formed by the support plate and the substrate.
Adjustment to rotate the translucent plate in the sub-scanning direction.
The bee according to claim 1, further comprising an adjusting screw.
Scanning device.