JPH09187984A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To scan a plurality of laser beam sources by simple constitution by putting a plurality of beams from laser beam sources different in wavelength on the same optical axis of an optical system using a scanning lens free from chromatism and irradiating a surface to be scanned with laser beams emitted through an optical system having wavelength resolving function. SOLUTION: Laser modules LD1-LD3 being a plurality of laser beam sources are put on the same optical axis by reflecting mirrors 1-3 and laser beams are incident on a scanning system composed of an optical lens free from chromatism such as a polygon mirror 4 or an fθ lens 5 and passed through cover glass or a diffraction lattice 6 having wavelength resolving function to perform scanning on a photosensitive drum 7 a plurality of times. The laser beams emitted from laser modules LD1-LD3 different in wavelength may be separated by the prism provided immediately before the photosensitive drum 7 to irradiate the different positions of the photosensitive drum 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device for scanning a plurality of beams used in a laser beam printer or the like.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a scanning optical device using a plurality of laser beams as a light source used in a color laser printer or the like.

For example, by arranging a plurality of laser light emitting ends,
There is one used in one optical system.

As a first technique, as shown in FIG. 5, two laser module LDs, which are laser light sources, are prepared.
The beam is incident on the fθ lens 13 via the beam splitter or half mirror 11 and the polygon mirror 12 shown in FIG. The two beams emitted from the LD are scanned by lowering the rotation speed of the polygon mirror 12 or increasing the scanning line density.

At this time, a beam splitter or a half mirror 11 is used as a separating optical system which commonly uses two laser light sources, but it is expensive.

The second technique is to use a laser having two light emitting sources in one laser module LD.

As a third technique, as shown in FIG. 7, a laser module LD, which is a plurality of laser light sources, has a plurality of optical systems such as a plurality of cylindrical lenses 14, a plurality of polygon mirrors 15, a plurality of fθ lenses 16, and the like. Drum 17
There is one that scans the top.

[0008]

However, in the case of the first technique, it is difficult to manage the optical axes of the laser modules LD1 and LD2 at intervals of several tens of μm. Increasing the accuracy of parts and assembling will increase the cost. When two beams pass through one scanning optical system, the pitch of the two beams on the image plane changes depending on whether the lens is good or bad. Then, fine adjustment is required for each unit.

Next, in the case of the second technique, since one scanning optical system is used, there is a problem similar to the first technique. Moreover,
Since the pitch of the light emitting points is pre-made and cannot be finely adjusted, restoration is impossible.

The third technique is better than the first and second techniques in that each of the two can be adjusted, but the magnification due to the variation of the scanning lens cannot be adjusted. In addition, there are many component parts, resulting in high cost. Requires a large amount of space. Also, a large number of polygon motors or special ones are required.

A system capable of scanning a plurality of beams on the same optical axis is not possible with the above method.

In view of the above problems, it is an object of the present invention to provide a scanning optical device capable of scanning a plurality of laser light sources having a simple structure.

[0013]

In order to solve the above problems, the present invention places a plurality of beams from laser light sources having different wavelengths on the same optical axis of an optical system using a scanning lens having no chromatic aberration. The scanning optical device is configured so that the irradiation to the surface to be scanned is emitted through the optical system having the wavelength resolution function.

[0014]

Embodiments of the present invention will be described below.

FIG. 1 is an explanatory view showing the configuration of the scanning optical device of the present invention.

Laser modules LD1 to LD3, which are a plurality of laser light sources, are placed on the same optical axis by reflection mirrors 1 to 3, and are incident on a scanning system composed of an optical lens having no chromatic aberration such as a polygon mirror 4 and an fθ lens 5, and the wavelength is set. A plurality of scans can be performed on the photoconductor drum 7 through a cover glass having a decomposition function and the diffraction grating 6.

[0017]

FIG. 2 shows an embodiment of a scanning optical device according to the present invention, in which laser beams LD1 to LD3 having different wavelengths are emitted from laser modules LD1 to LD3 by a prism 8 provided immediately before a photosensitive drum 7. Light is separated and applied to different positions on the photosensitive drum 7. FIG. 3 shows the prism 8
FIG. 3 is an explanatory diagram showing how white light is separated.

FIG. 4 shows another embodiment of the present invention, in which laser modules LD1 to LD are used as means for injecting a plurality of beams.
A prism 9 is used between 3 and the polygon mirror 4. As described above, according to the present invention, it is possible to put a plurality of beams on the same optical axis and pass through the optical system by applying the property that the prisms 8 and 9 and the diffraction grating 6 perform wavelength resolution.

[0019]

As described above, according to the present invention, a plurality of laser beams can be aligned on the same optical axis. Easy to adjust. Since only one scanning optical lens is required, it is cost effective. Dispersion space that does not vertically stack the lenses as shown in the prior art.

Although there are diffraction gratings, prisms and the like as parts for wavelength decomposition, it is possible to make resin advantageous in terms of cost and shape.

The cover glass can be substituted and the number of parts can be reduced.

An optical system for scanning multiple beams, 1
One scanning optical system can align the optical axes of multiple beams with the optical axes of the scanning optical system.

Further, since the optical axes are the same, the component accuracy and the installation accuracy can be handled in the same manner as the optical system of the current printer, and the cost and space can be saved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a scanning optical device of the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of a scanning optical device of the present invention.

FIG. 3 is an explanatory diagram showing how a prism 8 separates white light.

FIG. 4 is an explanatory view showing another embodiment of the present invention.

FIG. 5 is a configuration diagram showing a conventional scanning optical device.

FIG. 6 is a configuration diagram showing a conventional scanning optical device.

FIG. 7 is a configuration diagram showing a conventional scanning optical device.

[Explanation of symbols]

 1 Reflection Mirror 2 Reflection Mirror 3 Reflection Mirror 4 Polygon Mirror 5 fθ Lens 6 Diffraction Grating 7 Photosensitive Drum 8 Prism 9 Prism 11 Beam Splitter or Half Mirror 12 Polygonal Mirror 13 fθ Lens 14 Cylindrical Lens 15 Polygon Mirror 16 fθ Lens 17 Photosensitive Body Drum LD, LD1, LD2, LD3 Laser module

Claims (1)

[Claims] 1. An optical system having a wavelength resolving function for irradiating a surface to be scanned with a plurality of beams from a plurality of laser light sources having different wavelengths placed on the same optical axis of an optical system using a scanning lens having no chromatic aberration. A scanning optical device characterized in that the scanning optical device is configured to emit light through the scanning optical device.