KR100571809B1 - Laser scanning apparatus - Google Patents

Abstract

An optical scanning device is disclosed. The disclosed optical scanning device includes a laser diode array in which a plurality of laser diodes are arranged at predetermined intervals in the sub-scanning direction to form an array, and a laser beam is emitted, and the beams emitted from the laser diode array are deflected at a predetermined angle on the photosensitive drum. At least one beam deflector is provided for forming a light spot at a specific portion in the main scanning direction. According to such a configuration, the polygon mirror is not used, so noise, vibration, and heat problems are not generated, and power consumption can be reduced, and the use of a laser diode array can cope with high speed and high resolution of a laser printer. have.

Description

Optical scanning device

1 is a view showing a schematic configuration of a conventional optical scanning device,

2 is a perspective view schematically showing the configuration of an optical scanning device according to a first embodiment of the present invention;

3 is a perspective view of the microlens integrated laser diode array shown in FIG. 2;

4 is a view showing the operation of the optical scanning device shown in FIG.

5 is a view showing refraction of a laser beam in a beam deflector made of a material exhibiting an electric field-optical effect,

6 shows the refraction of a laser beam in a beam deflector made of a material exhibiting an acoustic-optical effect,

7 is a view schematically showing the configuration of an optical scanning device according to a second embodiment of the present invention;

8 is a view schematically showing the configuration of an optical scanning device according to a third embodiment of the present invention;

9 is a diagram schematically showing a configuration of an optical scanning device according to a fourth embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

110,210 ... Micro Lens Integrated Laser Diode Array

111,211 ... laser diodes 112 ... laser diode arrays

113 ... Microlens 114 ... Microlens Array

130,230,330,430 ... beam deflector 140,240,340,440 ... imaging optical system

150,250,350,450 ... reflective mirror 160,260,360,460 ... photosensitive drum

220,320 ... optical system

The present invention relates to an optical scanning device, and more particularly, to an optical scanning device that can be miniaturized by using a laser diode array and a beam deflector in which microlenses are integrated, and at the same time increase the printing speed.

In general, a laser printer forms an electrostatic latent image by imaging a laser beam emitted from a laser diode by a video signal of an input image on a photosensitive drum, and sprays toner on the electrostatic latent image to be transferred to a printing medium such as printing paper. It is a device that reproduces an image.

Such a laser printer includes an optical scanning device that emits a laser beam and forms an image on a photosensitive drum.

1 is a view showing a schematic configuration of a conventional optical scanning device.

Referring to FIG. 1, an optical scanning device includes a laser diode 10 emitting a laser beam, a collimating lens 11, and a collimating lens that makes the beam emitted from the laser diode 10 parallel to an optical axis. Cylinder lens 12 which makes the parallel light through 11 into the horizontal light with respect to the sub-scanning direction, and the plurality of half which scans by moving the linear light in the horizontal direction through the cylinder lens 12 at an isotropic speed F-θ lens 14 for focusing on the photosensitive drum 16 by polarizing light at an isotropic velocity through the polygon mirror 13 and polygon mirror 13 having a slope in the main scanning direction and correcting spherical aberration and a reflection mirror 15 for reflecting the laser beam through the f-θ lens 14 in the horizontal direction.

The rotated polygon mirror 13 reflects while varying the angle of the light beam to form a desired image in the main scanning direction of the photosensitive drum 16.

 In recent years, laser printers have been developed in the direction of high speed and high resolution. In a conventional optical mirror using a polygon mirror, the laser diode on-time frequency of the optical scanner and the number of revolutions per minute of the polygon mirror driving motor are increased when the resolution and printing speed of the laser printer are increased by n times for high speed and high resolution. Must be increased by n times.

However, increasing the number of revolutions per minute of the polygon mirror drive motor by n times is not easy and the cost is increased. In addition, the noise is increased due to the flow resistance of the internal air due to the high speed rotation of the polygon mirror driving motor.

To solve these problems, other alternatives have been devised to replace polygon mirrors, one of which uses a vertical-cavity surface-emitting laser diode array or LED array and employs direct or suitable optics. To expose the photosensitive drum.

However, the above methods can overcome the disadvantages by eliminating the polygon mirror, but the cost is greatly increased because the use of surface-emitting laser diode array or LED array equipped with thousands of elements to increase the resolution. In addition, the same number of collimating lens arrays are required to turn the light into parallel light, and because the alignment of the laser beam and the lens array is difficult, a large amount of time is consumed and an additional device has to be installed, which increases production costs. Is generated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. Instead of a polygonal lens, a beam deflector is used to directly expose a beam onto a photosensitive drum, and light can be increased in resolution and printing speed by using a predetermined number of micro lens integrated laser diode arrays. The object is to provide an injection device.

In order to achieve the above object, the optical scanning device of the present invention comprises a laser diode array in which a plurality of laser diodes are arranged at predetermined intervals in the sub-scanning direction to form an array, and emit a laser beam, and a beam emitted from the laser diode array is predetermined. At least one beam deflector for deflecting at an angle to form a light spot at a particular site in the main scanning direction on the photosensitive drum.

According to the present invention, the laser diode array is integrally coupled with the same number of micro lenses which make the emitted beam into parallel light.

According to the invention, the laser diode is a surface emitting laser.

delete

According to the invention, the beam deflector is composed of a material exhibiting the field-optical effect.

According to the present invention, the beam deflector is composed of any one selected from lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), KDP (potassium dihydrogen phosphate; KH ₂ PO ₄ ), and SBN (Strontium Barium Niobate) Crystal It is.

According to the invention, the beam deflector is composed of a material exhibiting an acoustic-optical effect.

According to the present invention, the beam deflector is composed of any one selected from fused-quartz and flint glass.

According to the present invention, a plurality of beam deflectors are arranged at predetermined intervals in a direction in which light travels.

According to the present invention, the beam deflector is made of a material having different refractive indices.

According to the invention, the beam deflector is made of a material having the same refractive index.

According to the present invention, an imaging optical system is further disposed in front of the beam deflector to correct spherical aberration of light passing through the beam deflector to form an image on the photosensitive drum.

According to another feature of the present invention, a plurality of laser diodes are arranged in a sub-scanning direction at a predetermined interval to configure a laser diode array for emitting a laser beam, and to deflect the beam emitted from the laser diode array at a predetermined angle At least one beam deflector for forming a light spot at a specific portion in the main scanning direction on the photosensitive drum, and an optical system disposed between the light source and the beam deflector to make the beam emitted from the light source into parallel light.

delete

According to the invention, the beam deflector is composed of a material exhibiting the field-optical effect.

According to the present invention, it is further provided with an amplifying optical system installed in front of the beam deflector to increase the angle of the light passing through the beam deflector.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a perspective view schematically showing the configuration of an optical scanning device according to a first preferred embodiment of the present invention, FIG. 3 is a perspective view showing the microlens integrated laser diode array shown in FIG. 2, and FIG. Figure 2 is a side view showing the operation of the optical scanning device shown in Figure 2, Figure 5 is a view showing the refraction of the laser beam in a beam deflector made of a material exhibiting an electric field-optical effect, Figure 6 is made of a material exhibiting an acoustic-optical effect A diagram showing the refraction of the laser beam in the beam deflector.

First, referring to FIG. 2, the optical scanning device deflects a light source 110 that emits a laser beam and a beam emitted from the light source 110 at a predetermined angle so that the main scanning direction (arrow) is on the photosensitive drum 160. At least one beam deflector 130 for forming a light spot on a specific portion in the A direction) and a reflection mirror 150 for reflecting the laser beam to the photosensitive drum 160.

An imaging optical system 140 is further disposed between the beam deflector 130 and the reflection mirror 150 to correct spherical aberration of light passing through the beam deflector 130 to form an image on the photosensitive drum 160. It is preferable.

As illustrated in FIG. 3, the light source 110 is an array in which a plurality of laser diodes 111 are arranged at predetermined intervals and are integrally formed. The laser diode array 112 is formed by forming a plurality of laser diodes on a wafer using a semiconductor process, and cutting a plurality of laser diodes.

The laser diode array 112 is coupled to a microlens array 114 in which the same number of microlenses 113 as the laser diode 111 are integrally arrayed. The microlens array 114 is formed using a semiconductor process similarly to the laser diode array 112.

The laser diode 111 is preferably a surface emitting laser. The microlens 113 makes the beam emitted from the laser diode 111 into parallel light.

The laser diode array 112 is preferably provided with a plurality of laser diodes in the sub-scanning direction (arrow B direction). This is because the laser beam radiated from the laser diode array 112 is radiated in the main scanning direction (arrow A direction) and in the sub scanning direction (arrow B direction) because the laser beam is also radiated in the sub scanning direction (arrow B direction). The laser beam is emitted as much as the number of the laser diodes 111 arranged to improve the scanning speed.

For example, when five microlens integrated laser diodes are arranged in the sub-scanning direction (arrow B direction), 5 sub-scanning directions in one main scanning direction (arrow A direction) scanning are performed on the photosensitive drum 160. It can be scanned to increase printing speed by five times.

The beam deflector 130 is a device capable of deflecting the input beam in a desired specific direction. The beam is incident by changing the magnitude of the voltage supplied thereto using a material exhibiting an electric field-optical effect as shown in FIG. 5. The path of is changed to a predetermined angle.

The relationship between the voltage (Ｖ) supplied and the angle (α) to be refracted is calculated as shown in [Equation 1] below.

[Equation 1]

Where n is the refractive index of the field-optic

        E is the strength of the electric field

는 전계-광학계수

Is electric field-optical coefficient

        인가 is the applied voltage

       d is the length of the field-optical material

Therefore, by adjusting the voltage applied to the beam deflector from the outside, the intensity E of the electric field is adjusted as shown in [Equation 1], and the refractive angle α is also changed in proportion thereto. Therefore, as the laser beam passes through the deflector 130, the angle of refraction α changes according to the applied voltage Ｖ.

The desired image can be obtained by exposing the laser beam to the photosensitive drum 160 in the main scanning direction while controlling the refractive angle α by adjusting the applied voltage.

The electric field-optic material may be used as long as the material exhibits an electric field-optical effect in which the refraction angle α may change with respect to an applied voltage, ie, lithium niobate (LiNbO ₃ ) or lithium tantalate. (LiTaO ₃ ), KDP (potassium dihydrogen phosphate; KH ₂ PO ₄ ), and SBN (Strontium Barium Niobate) Crystals are preferably used.

In addition, as shown in FIG. 6, the beam deflector 130 changes the angle of the incident beam to a predetermined angle by applying an acoustic wave having a specific frequency thereto using a material having an acoustic-optical effect.

The relationship between the applied acoustic wave and the angle of refraction is calculated as shown in [Equation 2] below.

[Equation 2]

2α = ｆ ＊ (λ / Ｖ _s )

Where α is the angle of refraction

        frequency of acoustic waves

        λ is the wavelength of light in the material

Ｖ _s is the velocity of the acoustic wave in the acoustic-optical material

Therefore, the frequency of the acoustic wave is a small wave and a dense place as the longitudinal wave, and the refraction angle is deflected when the laser beam passes through the small and dense place. Therefore, the refraction angle α is also changed in proportion to this by adjusting the frequency of the acoustic wave applied from the outside. Therefore, as the laser beam passes through the deflector 130, the angle of refraction α is changed.

The desired image can be obtained by exposing the laser beam to the photosensitive drum 160 in the main scanning direction while adjusting the refraction angle α by adjusting the frequency of the acoustic wave.

The acoustic-optical material may be used as long as the material produces an acoustic-optical effect in which the angle of refraction α may change with respect to the frequency of the acoustic wave. In particular, the acoustic-optic material is preferably selected from any one of fused-quartz, flint glass.

Preferably, a plurality of beam deflectors 130 are disposed at predetermined intervals in a direction in which the laser beam travels. This is because the material used for the beam deflector 130 has an inherent refractive index (n). When the material cannot be refracted to the extent that the width of the photosensitive drum 160 can be exposed, a plurality of beams The deflector 130 is disposed to obtain a refractive angle α that can expose the photosensitive drum 160.

Accordingly, since the plurality of beam deflectors 130 may obtain a refractive angle α for exposing the photosensitive drum 160, the materials used in the beam deflectors 130 may have the same refractive index n. It may have a different refractive index n. A plurality of beam deflectors 130 may be appropriately arranged to obtain a desired angle of refraction α.

Meanwhile, in FIG. 2, an image is formed between the beam deflector 130 and the photosensitive drum 160 to polarize the laser beam passing through the beam deflector 130 in the main scanning direction and to correct spherical aberration to focus on the scanning surface. An optical system (ie, a ｆ-θ lens) may be further provided.

The operation of the optical scanning device according to the first embodiment of the present invention having the above configuration will be described with reference to the drawings.

2 and 4, when the laser beam is emitted from the micro lens integrated laser diode array 110, the laser beam travels parallel to the optical axis. The laser beam emitted from the micro lens integrated laser diode array 110 is incident on the beam deflector 130. When the beam deflector 130 uses an electric field-optical material, the beam deflector 130 adjusts the refractive angle α of the laser beam by adjusting a voltage applied from an external power source, thereby adjusting the refractive angle α of the laser beam by the laser beam in the main scanning direction (arrow A direction). The surface of the photosensitive drum 160 is exposed.

When the beam deflector 130 uses an acoustic-optical material, by applying an acoustic wave having a specific frequency, the beam deflector 130 adjusts the refractive angle of the laser beam incident at a predetermined angle to the laser beam in the main scanning direction (arrow A direction). As a result, the surface of the photosensitive drum 160 is exposed.

In this case, the microlens-integrated laser diode array 110 has a plurality of laser diodes 111 arranged in a sub scanning direction (arrow B direction), that is, in a direction in which the photosensitive drum 160 rotates. By scanning once, a plurality of scanning in the sub-scanning direction can also speed up printing.

7 is a diagram schematically showing the configuration of an optical scanning device according to a second embodiment of the present invention. The basic configuration of the second embodiment is similar to that of the first embodiment shown in FIGS. 2 and 4, except that a microlens is not integrally formed in the laser diode, so that the optical system 220 makes the laser beam into parallel light separately. That is, the collimating lens is disposed between the light source 210 and the beam deflector 230 is different.

Referring to FIG. 7, the optical scanning device deflects a light source 210 emitting a laser beam and a beam emitted from the light source 210 at a predetermined angle to a specific portion in the main scanning direction on the photosensitive drum 260. Optical system 220 disposed between at least one beam deflector 230 and the light source 210 and the beam deflector 230 to form a light spot to make the laser beam emitted from the light source 210 into parallel light And a reflection mirror 250 for reflecting the laser beam in the horizontal direction.

 The light source 210 is an array in which a plurality of laser diodes 211 are arranged at predetermined intervals. The laser diode array is formed by forming a plurality of laser diodes using a semiconductor process on a wafer, and then cutting them together by a plurality of laser diodes.

The laser diode 211 is preferably a surface emitting laser. In the laser diode array 210, a plurality of laser diodes 211 is preferably arranged in the sub-scanning direction. This is because the laser beam is emitted in the main scanning direction at the same time as the laser beam is emitted in the sub-scanning direction in the laser diode array 210, so that the number of laser beams corresponding to the number of the laser diodes 211 arranged in the sub-scanning direction By radiating, the scanning speed can be improved.

Since the configuration of the beam deflector 230 is the same as that shown in the first embodiment, a description thereof will be omitted.

An imaging optical system (i.e., ｆ) that polarizes the laser beam passing through the beam deflector 230 in the main scanning direction and corrects spherical aberration between the beam deflector 230 and the photosensitive drum 260. -θ lens) 240 may be further provided.

The operation of the optical scanning device according to the second embodiment of the present invention having the above configuration will be described with reference to the drawings.

Referring to FIG. 7, the laser beam emitted from the laser diode array 210 travels parallel to the optical axis while passing through the optical system 220. The laser beam passing through the optical system 220 is incident on the beam deflector 230. When the beam deflector 230 uses an electric field-optical material, the beam deflector 230 adjusts the voltage applied from an external power source to adjust the refractive angle of the laser beam to expose the surface of the photosensitive drum 260 in the main scanning direction.

When the beam deflector 230 is made of an acoustic-optical material, the surface of the photosensitive drum 260 in the main scanning direction is controlled by adjusting an angle of refraction of a laser beam incident at a predetermined angle by applying an acoustic wave having a specific frequency. Is exposed.

In this case, since the plurality of laser diodes 211 are arranged in the sub-scanning direction, that is, in the direction in which the photosensitive drum 260 rotates, the laser diode array 210 scans the sub-scanning direction as one scan in the main scanning direction. Also, a plurality of scans can be used to speed up printing.

8 is a diagram schematically showing the configuration of an optical scanning device according to a third embodiment of the present invention. The basic configuration of the third embodiment is similar to that of the second embodiment shown in FIG. 7, except that an amplifying optical system 370 is further disposed between the deflector 330 and the imaging optical system 340 to increase the angle of light. It is.

Referring to FIG. 8, the optical scanning device deflects a light source 310 emitting a laser beam and a beam emitted from the light source 310 at a predetermined angle to a specific portion in the main scanning direction on the photosensitive drum 360. Optical system 320 disposed between the at least one beam deflector 330 and the light source 310 and the beam deflector 330 to form a light spot to make the laser beam emitted from the light source 310 into parallel light And a reflection mirror 350 for reflecting the laser beam in the horizontal direction.

 The light source 310 is an array in which a plurality of laser diodes 311 are arranged at predetermined intervals. The laser diode array 310 is formed by forming a plurality of laser diodes using a semiconductor process on a wafer, and cutting a plurality of laser diodes.

In the laser diode array 310, a plurality of laser diodes 311 are preferably arranged in the sub-scanning direction. This is because the laser beam is emitted in the main scanning direction at the same time as the laser beam is emitted in the sub-scanning direction in the laser diode array 310, so that the number of laser beams corresponding to the number of the laser diodes 311 arranged in the sub-scanning direction By radiating, the scanning speed can be improved.

Since the configuration of the beam deflector 330 is the same as that shown in the second embodiment, description thereof will be omitted.

An imaging optical system that polarizes the laser beam passing through the beam deflector 330 in the main scanning direction between the beam deflector 330 and the photosensitive drum 360 and corrects spherical aberration to focus on the scanning plane. -θ lens) 340 may be further provided.

An amplifying optical system 370 is further provided between the beam deflector 330 and the imaging optical system 340 to further increase the angle of the light emitted from the beam deflector 330. Since the amplification optical system 370 makes the angle of light larger, the angle of light can be made larger even when the number of the beam deflectors 330 is not used.

Since the operation of the optical scanning device according to the third embodiment of the present invention is similar to that of the second embodiment described above, a detailed description of the operation will be omitted.

9 is a diagram schematically showing the configuration of an optical scanning device according to a fourth embodiment of the present invention. The basic configuration of the fourth embodiment is similar to that of the first embodiment shown in FIG. 4, except that an amplifying optical system 470 is further disposed between the deflector 430 and the imaging optical system 440 to increase the angle of light. It is.

Referring to FIG. 9, the optical scanning device deflects a light source 410 emitting a laser beam and a beam emitted from the light source 410 at a predetermined angle to light a specific portion in the main scanning direction on the photosensitive drum 460. An optical system 420 disposed between the at least one beam deflector 430 and the light source 410 and the beam deflector 430 to form a spot, and the laser system emitted from the light source 410 into parallel light; It is composed of a reflecting mirror 450 for reflecting the laser beam in the horizontal direction.

In the light source 410, the same number of micro lenses 113 as the plurality of laser diodes 111 are integrally coupled to form an array.

In the laser diode array 410, a plurality of laser diodes 411 are preferably arranged in the sub-scanning direction. This is because the laser beam is emitted in the main scanning direction at the same time as the laser beam is emitted in the sub-scanning direction in the laser diode array 410, so that the number of laser beams corresponding to the number of the laser diodes 411 arranged in the sub-scanning direction By radiating, the scanning speed can be improved.

Since the configuration of the beam deflector 330 is the same as that shown in the first embodiment, description thereof will be omitted.

An imaging optical system that polarizes the laser beam passing through the beam deflector 430 in the main scanning direction between the beam deflector 430 and the photosensitive drum 460 and corrects spherical aberration to focus on the scanning plane ( -θ lens) 440 may be further provided.

An amplification optical system 470 is further provided between the beam deflector 430 and the imaging optical system 440 to further increase the angle of the light emitted from the beam deflector 430. Since the amplification optical system 470 makes the angle of light larger, the angle of light can be made larger even if the number of the beam deflectors 330 is not used.

Since the operation of the optical scanning device according to the fourth embodiment of the present invention is similar to that of the first embodiment described above, a detailed description of the operation will be omitted.

As described above, the optical scanning device according to the present invention

First, the use of a polygon mirror eliminates the need for a driving motor, which eliminates noise, vibration, and heat problems, as well as reducing power consumption.

Second, the manufacturing cost can be lowered by using a significantly smaller number of laser diodes than the direct exposure method of laser or LED array.

Third, there is an effect that can cope with the high speed and high resolution of the laser printer by using a laser diode array.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary and will be understood by those of ordinary skill in the art that various modifications and variations can be made therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (24)

A laser diode array in which at least one laser diode is arranged at a predetermined interval in the sub-scanning direction to form an array to emit a laser beam; And at least one beam deflector for deflecting the beam radiated from the laser diode array at a predetermined angle to form a light spot at a specific portion in a main scanning direction on the photosensitive drum. The method of claim 1, The laser diode is an optical scanning device, characterized in that the surface-emitting laser diode. The method of claim 1, And the same number of micro lenses are integrally coupled to the laser diode array to make the emitted beam into parallel light. delete The method of claim 1, The beam deflector is An optical scanning device, comprising: a material exhibiting an electric field-optical effect. The method of claim 5, The beam deflector is An optical injection device comprising any one selected from lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), KDP (potassium dihydrogen phosphate; KH ₂ PO ₄ ), and SBN (Strontium Barium Niobate) Crystal. The method of claim 1, The beam deflector is Optical scanning devices, characterized by consisting of materials exhibiting an acoustic-optical effect The method of claim 7, wherein       The beam deflector is optical scanning device, characterized in that composed of any one selected from fused-quartz, flint glass. The method of claim 1, The beam deflector is At least one or more optical scanning devices are arranged at predetermined intervals in a direction in which light travels. The method of claim 9, The beam deflector is Optical scanning device, characterized in that made of a material having a different refractive index. The method of claim 9, The beam deflector is Optical scanning device, characterized in that made of a material having the same refractive index. The method of claim 1, And an imaging optical system for correcting spherical aberration of light passing through the beam deflector to form an image on the photosensitive drum in front of the beam deflector. A laser diode array in which at least one laser diode is arranged at a predetermined interval in the sub-scanning direction to form an array to emit a laser beam; At least one beam deflector for deflecting the beam radiated from the laser diode array at a predetermined angle to form a light spot at a specific portion in a main scanning direction on the photosensitive drum; And an optical system disposed between the light source and the beam deflector to make the beam radiated by the light source into parallel light. The method of claim 13, The laser diode is an optical scanning device, characterized in that the surface-emitting laser diode. delete The method of claim 13, The beam deflector is An optical scanning device, comprising: a material exhibiting an electric field-optical effect. The method of claim 13, The beam deflector is An optical injection device comprising any one selected from lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), KDP (potassium dihydrogen phosphate; KH ₂ PO ₄ ), and SBN (Strontium Barium Niobate) Crystal. The method of claim 13, And the beam deflector is made of a material exhibiting an acoustic-optical effect. The method of claim 18, The beam deflector is optical scanning device, characterized in that composed of any one selected from fused-quartz, flint glass. The method of claim 13, The beam deflector is At least one or more optical scanning devices are arranged at predetermined intervals in a direction in which light travels. The method of claim 20, The beam deflector is Optical scanning device, characterized in that made of a material having a different refractive index. The method of claim 20, The beam deflector is Optical scanning device, characterized in that made of a material having the same refractive index. The method of claim 13, And an imaging optical system for correcting spherical aberration of light passing through the beam deflector to form an image on the photosensitive drum in front of the beam deflector. The method according to claim 1 or 13, And an amplifying optical system installed in front of the beam deflector to increase the angle of light passing through the beam deflector.

Images