JPS62226117A - Optical scanning device - Google Patents

Abstract

PURPOSE:To set optionally intervals of a beam on an image carrier in a subscanning direction and to facilitate synchronization with a beam detection signal by providing a means which makes plural beams into parallel light and a prism which vary beam intervals of the parallel light optically. CONSTITUTION:Divergent light from a semiconductor laser array 11 as a light source is made into parallel beams L1-L4 by a collimator lens 12 and those parallel beams are incident on the prism 17. The prism 17 is a triangular prism, the incidence surface 171 and projection surface 172 for the beams slant to each other, and the beams diffracted by the incidence surface 171 travel straight in the prism as they are and are refracted again by the projection surface 172. Further, the angle of incidence of the parallel beams is varied to vary parallel beam intervals Pe at the time of incidence to intervals Ps of projection beams B1-B4 at the time of projection. Thus, the angle of incidence on the prism 17 is selected properly to vary the intervals Ps of the projection beams.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a scanning optical device used in a laser beam printer, etc., and more particularly to a scanning optical device that scans a plurality of beams emitted from a light source onto an image carrier. Regarding.

(Prior Art) Generally, in a laser beam printer in which a light beam is scanned on a scanning medium (image carrier) by a polygon mirror, it is necessary to increase the rotation speed of the polygon mirror in order to improve the scanning speed. , or the number of surfaces of the polygon mirror had to be increased. However, increasing the rotation speed of the polygon mirror as described above has a limit to the rotation speed of the scanner motor for rotating and removing the polygon mirror. Furthermore, when the number of surfaces of the polygon mirror is increased, the diameter of the polygon mirror becomes larger, which increases the load applied to the scanner motor □.

Therefore, conventionally, it has been considered to provide a plurality of light sources and scan the scanned medium E with a plurality of spots. In other words, a so-called array light source that has semiconductor lasers with light-emitting points that can be driven independently can record multiple scanning lines at the same time, enabling high-speed printing. Often, the image clock frequency for printing can also be lowered. Further, since the output of the semiconductor laser may be low, it is advantageous against deterioration.

The multi-beam laser beam printer as described above is shown in FIG. 4. In FIG. 4, 101 is a semiconductor laser array in which a plurality of semiconductor lasers are arranged in a line;
is a condensing lens (collimator lens) that converts the diverging light from the semiconductor laser array 101 into parallel beams LL, L2°L3, L4, and lO3 converts the diverging light from the semiconductor laser array 101 into parallel beams L1. L2. L3゜L
4 is a polygon mirror (rotating polygon mirror) that scans and extends onto the photoreceptor drum 105, 104 is an fθ lens that forms an image of the scanning beam scanned by the polygon mirror 103 on the photoreceptor drum 105, and 106 is a plurality of A reflector 109 is placed near the tip of the scanning line to guide the scanning beam to the beam detector 108, and a light blocking plate 109 is used to accurately detect the deflection of the beam. The beam detector 108 is irradiated with the light that was blocked when crossing the beam, and the beam detector 108 outputs an electrical signal corresponding to the beam irradiation.

Further, FIG. 5(A) shows the arrangement of the light emitting points Bl-B4 of the semiconductor laser array 101.
are lined up in a direction perpendicular to the scanning direction sL, and therefore the scanning pitch (pixel interval) P on the photosensitive drum 105
s is uniquely determined by the interval Pe between the light emitting points B1 to B4. That is, in this case, the light emitting point B1
The arrangement interval Pe of ~B4 must be made equal to the pixel interval formed on the photoreceptor drum 105, and the pixel interval is dominated by the arrangement interval of the light emitting points Bl-B4.

(Problems to be Solved by the Invention) In the conventional example described above, the light emitting points B1 to B4 are connected to a straight line L perpendicular to the scanning direction SL, as shown in FIG.
- When tilted by an angle θ with respect to -L', the pixel spacing PS becomes P
s = P e X C0Iio,
An arbitrary pixel interval can be obtained by changing the angle θ, but in this case there is a problem that the beam scanning start position in the scanning direction must be changed for each beam.

Therefore, the present invention has been made to solve the above-mentioned problems of the conventional example, and its purpose is to maintain the alignment direction of the beams at right angles to the scanning direction, and to An object of the present invention is to provide a scanning optical device that can arbitrarily and easily change the beam spacing in the scanning direction.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a scanning optical device that scans a plurality of beams emitted from a light source onto an image carrier. It is constructed by comprising means for converting the beam into parallel light, and a prism for optically changing the beam interval of the parallel light.

(Function) In the present invention, a plurality of beams emitted from a light source are made into parallel lights by a means for making them parallel lights, and the beam interval of the parallel lights can be changed by a prism.

(Example) The present invention will be explained below based on the illustrated example. Third
The figure is a configuration diagram of a laser beam printer to which the present invention is applied. In the figure, l is CdS, amorphous silicon (A-3i
) or a photosensitive drum as an image carrier coated with a photosensitive layer such as OPC, 2 a laser scanning device for image exposure, 3 a primary charger, 4 a developer containing toner,
5 is a transfer charger, 6 is a cleaner, 7 is a pre-exposure lamp,
8 is a fixing device, and 9 is a cassette for storing transfer paper.

In the above configuration, the image forming process is performed as follows. First, the primary charger 3 charges the photoreceptor drum l rotating in the direction of the arrow to give a uniform potential, and then a laser beam emitted from the laser scanning device 2 is applied to the photoreceptor drum l. Exposure is performed according to the image information, and an electrostatic latent image is formed. Toner is attached to the latent image on the photosensitive drum 1 due to the potential difference between the latent image and the developing device 4, and the latent image is visualized. In this way, a toner image is formed on the photoreceptor drum l. This toner image is transferred from the back side of the transfer material (not shown) to a transfer charger 5.
By applying a corona charge of opposite polarity to the toner,
Transferred onto the tau material. The transfer material bearing the toner image is passed through a fixing device 8, so that the toner is fixed to the transfer material. On the other hand, toner and paper powder remaining on the photoreceptor drum l without being transferred are removed by a cleaner 6. Furthermore, the charge remaining on the photoreceptor drum 1 is
The static electricity is removed by exposure from the pre-exposure lamp 7. Thereafter, the same image process is repeatedly performed on the photosensitive drum 1 again.

FIG. 1 shows an embodiment of a scanning optical device according to the present invention,
In the figure, 11 is a semiconductor laser array as a light source, and the diverging light from this semiconductor laser array 11 is passed through a collimator lens 12 into parallel beams LL, L2, . L3. L
4, and these parallel beams Ll, L2 . L3. L4 enters the prism 17. Although the prism 17 is a triangular prism in the illustrated example, the beam entrance surface 17+ and the exit surface 172 are inclined with respect to each other, and the entrance surface 171
The beam refracted by the beam propagates straight through the prism and is refracted again by the exit surface 172. And Figure 2 (A), (B
), the parallel beam Ll.

By changing the incident angles at which L2, L3, and L4 enter, the parallel beam spacing re at the time of incidence is changed to
The output beam BL, B2. B3. The interval Ps of B4 is changed. In this way, by appropriately selecting the incident angle of incidence on the prism 17, the output beams Bl, B2 . B
3. The interval Ps of B4 can be changed. Incidentally, when fixing the support shaft 173 fixed to the prism 17 to its support body 174, the interval between the emitted beams can be adjusted by rotating and adjusting the prism 17. Further, 13 is an output beam Bl, B2 . B3. A polygon mirror (rotating polygon mirror) serves as a scanning means for scanning B4 onto the photoreceptor drum l, and the output beams B1 to B4 scanned by the polygon mirror 13 are sent onto the photoreceptor drum l by an fθ lens 14. imaged. In addition, the output beams Bl, B
2°B3. The alignment direction of B4 is the scanning direction by the polygon mirror 13 (direction perpendicular to the main scanning direction).

Reference numeral 16 indicates a reflecting mirror disposed near the tip of the scanning line to guide the emitted beam Bl-B4 to the beam detector 18. Reference numeral 19 indicates a light shielding plate for accurately detecting the position of the beam. The beam detector 18 is irradiated with the light that was blocked when crossing the edge, and the beam detector 18 outputs an electrical signal in response to the beam irradiation. Further, all of the output beams B1 to B4 enter the beam detector 18 substantially simultaneously. Then, after a predetermined period of time has elapsed from the generation of the electric signal, a drive current corresponding to the information signal to be recorded is applied to each light emitting section of the laser array, thereby emitting a laser beam modulated in accordance with the information signal.

(Effects of the Invention) The scanning optical device according to the present invention has the above configuration and operation, and includes means for converting a plurality of beams into parallel lights, and a prism for optically changing the beam interval of the parallel lights. Therefore, it is possible to arbitrarily set the beam spacing in the sub-scanning direction on the image carrier while the light sources are arranged perpendicularly to the beam scanning direction. This makes it easy to synchronize with the beam detection signal obtained by beam detection. Further, when changing the beam interval, it is possible to easily change the beam interval without being influenced by other factors.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a scanning optical device according to the present invention, FIGS. 2A and 2B are explanatory diagrams showing a beam passing through a prism in the same embodiment, and FIG. A configuration diagram of a laser beam printer to which the invention is applied, FIG. 4 is an explanatory diagram showing a conventional scanning optical device, and FIGS. FIG. Explanation of symbols 1... Photosensitive drum (image carrier) 11... Semiconductor laser array (light source) 12... Collimator lens (means for collimating light) 17... Prism Fig. 1 Fig. 2 ( A) " σ1 (B) 41st! Figure 5 (A) B4Nt) - L ', 33 5 Figure (B)

Claims (1)

[Claims] A scanning optical device that scans a plurality of beams emitted from a light source onto an image carrier, comprising means for converting the plurality of beams into parallel lights, and a prism for optically changing the beam interval of the parallel lights. A scanning optical device characterized by: