JPH06214174A - Optical scanning device - Google Patents

Abstract

PURPOSE:To arbitrarily change a dot diameter in the sub-scanning direction without changing a dot diameter in the main scanning direction. CONSTITUTION:A first and a second beams transmitted from two laser diodes are deflected by a deflector 9, a photosensitive body 16 is irradiated with the first beam through a lens system 10 for scanning, a cylindrical mirror 11 and a dot interval adjusting mirror 12 and the position adjacent to the first beam on the photosensitive body 16 is irradiated with the second beam through the lens system 10 for scanning, a cylindrical mirror 13, a turning mirror 14 and a bow compensating window 15. The angle of the dot interval adjusting mirror 12 is adjusted and the diameter in the sub-scanning direction of one dot obtained by synthesizing the first and the second beams is adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used in an image forming apparatus such as a laser printer or a copying machine, and in particular, the dot diameter in the sub-scanning direction can be changed according to the switching of the resolution. The present invention relates to an optical scanning device.

[0002]

2. Description of the Related Art In recent years, an electrophotographic method has been developed as a simple and high-quality printing method, and a laser printer apparatus, a copying machine and the like are available as apparatuses using this electrophotographic method. In these devices, an optical scanning device is used to form an electrostatic latent image on the photoconductor. In this optical scanning device, a scanning mirror having at least one reflecting surface is attached to the rotating shaft of a driving device and arranged on the emission optical path of a laser light source, and the reflecting surface of the scanning mirror is rotated by the driving force of the driving device. The emitted light of the laser light source is reflected to form scanning light, and the scanning light is irradiated onto the surface to be scanned of the photoconductor moving relatively in the non-scanning direction (sub-scanning direction) to form an electrostatic latent image. . And for example,
An image is formed by an electrophotographic method by developing the electrostatic latent image on the photoconductor with charged toner and transferring it to a printing paper.

By the way, the laser printer using the above-mentioned optical scanning device is required to have a function of changing the resolution according to the request of the printer host. In other words, if several types of hosts are connected to one printer, and if the resolution cannot be easily changed, the printing will be enlarged or reduced when the resolutions of the hosts are different. Proper printing cannot be done.
There are several types of host resolutions depending on cost performance. When the resolution is changed, the dot diameter irradiated on the surface to be scanned of the photoconductor is changed by a predetermined means, and the scanning speed and the modulation speed are changed.

As a means for changing the diameter of dots forming an electrostatic latent image on the surface to be scanned of the photosensitive member, Japanese Patent Laid-Open No. 3126/1990 is proposed.
Those disclosed in Japanese Patent Laid-Open No. 64 and Japanese Patent Laid-Open No. 57-164759 are known.

A first example of a conventional optical scanning device having a means for adjusting the dot diameter will be described with reference to FIGS. 15 to 17 as shown in, for example, Japanese Patent Laid-Open No. 3-212664. .

FIG. 15 is an explanatory view showing the structure of a general optical scanning device, and FIG. 16 is an explanatory view of the optical scanning device as seen from the axial direction of the photoconductor. In this optical scanning device, the beam emitted from the laser diode 101 is converted into a parallel light beam by the coupling lens 102, and the cylinder lens 10
3, the light is deflected by the deflector 105 having a rotary polygon mirror through the folding mirror 104, and passes through the scanning lens system 106, the folding mirror 107, and the cylinder mirror 108, and the photoconductor 1
09 is irradiated, and the photosensitive member 109 is scanned. Further, the beam on the scanning start end side and outside the scanning region is received by the photosensor 112 via the pickup mirror 110 and the lens 111, and a synchronization signal for controlling the image writing position is obtained.

FIG. 1 of Japanese Patent Application Laid-Open No. 3-212664 shows that in the general optical scanning device as described above, the amount of current passed through the laser diode 101 is changed to irradiate the surface to be scanned of the photoconductor 109. The optical output of the scanning light is Pa,
A circuit for switching to two stages of Pb is shown.

FIG. 17 is a characteristic diagram showing the optical outputs Pa and Pb. As shown in this figure, the light intensity
The diameter of the portion of the surface to be scanned above the threshold THL is Da when the optical output is Pa and Db when the optical output is Pb. As described above, in the first conventional example, by switching the light output between Pa and Pb, the electrostatic latent images having different resolutions are formed on the surface to be scanned by the dots of two kinds of diameters Da and Db. You can

Next, referring to FIGS. 18 and 19, a second optical scanning device having a conventional means for adjusting the dot diameter will be described.
As an example of the above, the one disclosed in Japanese Patent Laid-Open No. 57-164759 will be described.

FIG. 18 is an explanatory diagram showing a schematic structure of the optical scanning device. In this optical scanning device, the array laser 1
The light emitting portion 121A of the array laser 121 is arranged at the focal position of the collimator lens 122A.
B is arranged at a position deviated from the focal position of the collimator lens 122B. The beams emitted from the light emitting units 121A and 121B are collimated by the collimator lenses 122A and 122A.
After passing through B, it is deflected by the scanning mirror 123, and the imaging lens 1
An image is formed on the photosensitive member 125 by the image pickup device 24 at the same point or at two adjacent points at regular intervals.

FIG. 19 is a characteristic diagram showing the light intensity distribution of the image formation spot on the photoconductor 125. In this figure, A,
B indicates the intensity distribution of the image forming spot by the light emitting units 121A and 121B, respectively, and A + B indicates both the light emitting units 121A and 121B.
21B shows the intensity distribution of the imaging spot when 21B is made to emit light. Further, the threshold value D of the surface to be scanned of the photoconductor 125
The diameter of the portion above TH is D _{1 for} the strength distribution A, D _{2 for the} strength distribution B, and the strength distribution A + B
In case of, it becomes D ₃ . As described above, in the second conventional example, one or both of the light emitting units 121A and 121B are driven to set the output characteristic of the scanning light with which the surface to be scanned is irradiated with A,
B, by changing the three kinds of A + B, it is possible to cope with change of resolution by switching the dot diameter to three _{D 1, D 2, D 3} .

As described above, according to the first and second examples of the related art, the dot diameter for forming the electrostatic latent image on the surface to be scanned can be changed by a predetermined operation, so that high-resolution printing can be performed. It can be executed selectively.

[0013]

However, the optical scanning device of the first example requires a circuit for changing the intensity of light emitted from the laser light source, and this circuit electrically requires extremely high accuracy. , Difficult to implement. Further, there is a problem that the dot diameters in both the main scanning direction and the sub scanning direction change, and the dot diameter only in the sub scanning direction cannot be changed according to the switching of the resolution.

Further, in the optical scanning device of the second example, since the two beams are imaged at substantially the same point, only three kinds of resolutions corresponding to the light intensity can be obtained. Also, the dot diameters in both the main scanning direction and the sub scanning direction change, as in the first example. Further, since at least one of the two beams does not pass through the optical axis of the imaging lens 124, there is a problem that the scanning line is bent on the photoconductor.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical scanning device having a simple structure and capable of arbitrarily changing the dot diameter in the sub scanning direction without changing the dot diameter in the main scanning direction.

Another object of the present invention is to provide an optical scanning device capable of preventing the deflection of the scanning line from being generated in addition to the above objects.

[0017]

According to a first aspect of the present invention, there is provided an optical scanning device, wherein a light source section for generating a plurality of light beams and a light beam from the light source section are deflected to scan a surface to be scanned. A deflector, an imaging optical system that focuses each light beam deflected by the deflector to a close position on the surface to be scanned to form one dot, and a sub-beam of a plurality of light beams on the surface to be scanned. The adjusting means adjusts the interval in the scanning direction to adjust the diameter of the dots in the sub-scanning direction.

In this optical scanning device, a plurality of light beams from the light source section are deflected by the deflector and are focused by the imaging optical system at a close position on the surface to be scanned to form one dot. Further, the adjusting means adjusts the intervals of the plurality of light beams on the surface to be scanned in the sub-scanning direction, and adjusts the diameter of the dots in the sub-scanning direction.

An optical scanning device according to a second aspect of the present invention is the optical scanning device according to the first aspect, wherein the light source section generates a plurality of light beams having different optical characteristics, and the adjusting means and the imaging optical system and the object to be imaged. It has a mirror that is provided between the scanning surface and a plurality of reflecting surfaces that selectively reflect each light beam based on the optical characteristics of each light beam, and that the angle of the mirror with respect to each incident light beam is By changing the distance, the intervals of the plurality of emitted light beams in the sub-scanning direction are adjusted.

In this optical scanning device, by changing the angle of the mirror, the intervals between the plurality of light beams emitted from the mirror are adjusted, and the diameter of the dot in the sub-scanning direction is adjusted.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 8 relate to a first embodiment of the present invention.

FIG. 1 is an explanatory view showing the structure up to the scanning lens system of the optical scanning device of this embodiment, and FIG. 2 is an explanatory view showing the structure after the deflector of the optical scanning device of FIG.

As shown in FIG. 1, the optical scanning device of this embodiment has a laser diode 1 for emitting a first laser beam, a laser diode 2 for emitting a second laser beam, and each laser diode 1, Coupling lenses 3 and 4 for converting the outgoing beam of 2 into a parallel light flux, and a deflector 9 for deflecting each beam from the coupling lenses 3 and 4.
And folding mirrors 7 and 8 for making the beams from the coupling lenses 3 and 4 incident on the rotary polygon mirror of the deflector 9,
Cylinder lenses 5 and 6 which are provided between the coupling lenses 3 and 4 and the folding mirrors 7 and 8 and constitute a part of an optical system for correcting the surface tilt of the rotary polygon mirror of the deflector 9 are provided. .

As shown in FIG. 2, the optical scanning device further applies each beam deflected by the deflector 9 to the photosensitive member 16.
Constituting a scanning lens system 10 for forming an image on the upper part and a part of an optical system for reflecting the first beam emitted from the scanning lens system 10 and correcting the surface tilt of the rotating polygon mirror of the deflector 9. Cylinder mirror 11, a dot spacing adjusting mirror 12 capable of reflecting the first beam from the cylinder mirror 11 to guide it to the photoconductor 16 and adjusting the irradiation position of the first beam, and a scanning lens. A cylinder mirror 13 that constitutes a part of an optical system that reflects the second beam emitted from the system 10 and corrects the surface tilt of the rotating polygon mirror of the deflector 9, and the second beam from the cylinder mirror 13. A folding mirror 14 that reflects the light and guides it to the photoconductor 16, and a bow correction window 1 that is provided between the folding mirror 14 and the photoconductor 16 to correct the bending of the scanning line.
5 and.

FIG. 3 is an explanatory view showing the optical path of the first beam after the deflector of the optical scanning device of FIG. 1, and FIG. 4 shows the optical path of the second beam after the deflector of the optical scanning device of FIG. FIG. As shown in FIG. 3, the optical scanning device includes a deflector 9
Of the first beam deflected by the gap sensor mirror 20 that reflects the beam outside the scanning region, and the triangular slit 2 provided on the optical path of the reflected light of the mirror 20.
1 and a photo sensor 22. Similarly, as shown in FIG. 4, the optical scanning device includes a gap sensor mirror 23 that reflects a beam outside the scanning region of the second beam deflected by the deflector 9, and a light reflected by the mirror 23. It has a triangular slit 24 and a photo sensor 25 provided on the optical path. Triangular slits 21, 2
4 and the photosensors 22 and 25 are for detecting the interval between two dots on the photoconductor 16 by the two beams.

In this optical scanning device, the first beam emitted from the laser diode 1 is collimated by the coupling lens 3, passes through the cylinder lens 5 and the folding mirror 7, and is deflected by the deflector 9 for scanning. The photoconductor 16 is irradiated with light through the lens system 10, the cylinder mirror 11, and the dot spacing adjustment mirror 12. On the other hand, the second beam emitted from the laser diode 2 is made into a parallel light beam by the coupling lens 4, passes through the cylinder lens 6, the folding mirror 8 and is deflected by the deflector 9 to scan the lens system 10 for scanning and the cylinder mirror 13. , Folding mirror 14
And the first of the photoconductor 16 through the bow correction window 15
It is irradiated at a position close to the beam of.

In the image forming apparatus having this optical scanning device, the photoconductor 16 is uniformly charged according to a normal xerographic process, and the photoconductor 16 is statically charged on the photoconductor 16 by the beams modulated according to the image data. An electrostatic latent image is formed, and toner is attached to the electrostatic latent image by a developing device to make it visible as a toner image, and the toner image is transferred to a sheet by a transfer device.

In the present embodiment, the angle of the dot spacing adjusting mirror 12 is adjusted by a driving device (not shown) to adjust the irradiation position of the first beam on the photosensitive member 16, and thus the first beam and the second beam are adjusted. The diameter in the sub-scanning direction of one dot obtained by combining with the beam is adjusted. The distance between the dots formed by the first beam and the dots formed by the second beam on the photoconductor 16 is detected based on the outputs of the photosensors 22 and 25 shown in FIGS. 3 and 4.

Here, the triangular slit 21 and the photosensor 22 will be described in detail with reference to FIGS. The triangular slit 24 and the photo sensor 25 have the same structure.

FIG. 7 is a plan view of the triangular slit 21 and the photo sensor 22, and FIG. 8 is a side view thereof. As shown in these figures, the triangular slit 21 has a thickness of 100 μ, for example.
A 5 × 10 mm right-angled triangular hole is formed by etching in a stainless steel plate of m, and the photosensor 22 is provided on the back side of this hole. As shown in FIG. 8, a photo sensor drive board 23 that drives the photo sensor 22 is connected to the photo sensor 22. The triangular slit 21 and the photo sensor 22 are
In FIG. 7, the beam is arranged so as to cross in the direction indicated by reference numeral 24.

The photosensors 22 and 25 output a pulse having a width corresponding to the position where the beam passes through the holes of the triangular slits 21 and 24. 9A and 9B show photosensors 22 and 25 when the first beam and the second beam pass, respectively.
FIG. 3 shows an example of the output pulse of FIG. As shown in these figures, the pulse width when passing the first beam is t ₁ ,
Assuming that the pulse width when passing the beam of t is t ₂ , the ladder pattern or the like is printed in advance by the two beams and the relationship between the dot interval and t ₂ −t ₁ is obtained.
_The dot interval can be known from _2- t ₁ .

In this way, the photosensors 22 and 25 detect the dot spacing, and the feedback is applied to the driving device for driving the dot spacing adjusting mirror 12 so that the dot spacing becomes a desired value, and the dot spacing adjusting mirror 12 is fed back.
Adjust the angle of.

Next, referring to FIGS. 5 and 6, by changing the spacing between the dots formed by the first beam and the second beam, the diameter of one dot obtained by synthesizing these two dots is subdivided. The change in only the scanning direction will be described. In FIGS. 5 and 6, reference numeral 31 denotes the photoconductor 1.
6 shows the light intensity distribution of the first beam on 6,
Reference numeral ² indicates the light intensity distribution of the second beam on the photoconductor 16, and reference numeral 33 indicates the intensity level of 1 / e ² .

The dot spacing is adjusted by using the dot spacing adjusting mirror 12 shown in FIG. 7 with reference to the dot position of the second beam. In the following description, one dot diameter on the photoconductor is shown by combining two Gaussian beam profiles. For example, 240SPI
When resolutions up to 600 SPI are required, the first
The dot diameter of the second beam in the sub-scanning direction is 65 μm, and the dot diameter of the second beam in the sub-scanning direction is 50 μm. Then, in 600 SPI, only the second beam is turned on. This gives a dot diameter of 50 μm. Further, in 400 SPI, only the first beam is turned on. This gives a dot diameter of 65 μm. Further, in 300 SPI, both the first beam and the second beam are turned on, and the dot interval is 20 μm as shown in FIG.
Adjust to. This gives a dot diameter of 85 μm. In 240 SPI, both the first beam and the second beam are turned on, and the dot interval is set to 3 as shown in FIG.
Adjust to 0 μm. This gives a dot diameter of 95 μm. When both the first beam and the second beam are turned on and the dot spacing in the sub scanning direction is changed, the dot diameter in the main scanning direction hardly changes, and only the dot diameter in the sub scanning direction changes as described above. To do.

As described above, according to the present embodiment, since the dot diameter of the two beams is adjusted by adjusting the dot spacing in the sub-scanning direction, the dot diameter in the main-scanning direction is changed with a simple configuration. It is possible to arbitrarily change the dot diameter in the sub-scanning direction without performing the above.

The optical scanning device of this embodiment uses the laser modulation speed and the deflector 9 when switching the resolution.
It has a function to relatively change the rotation speed of. Further, in the present embodiment, the dot diameters of the first beam and the second beam are different, but the dot diameters may be the same. Also, 3
When more than the beam is used, the resolution can be switched over a wider range.

10 to 14 relate to the second embodiment of the present invention.

FIG. 10 is an explanatory diagram showing the overall structure of the optical scanning device of this embodiment, and FIG. 11 is an explanatory diagram of the optical scanning device of FIG. 10 seen from the axial direction of the photoconductor. As shown in these figures, the optical scanning device of this embodiment emits a first laser diode 41 which emits a P-polarized first beam 81 and a second laser diode 41 which emits an S-polarized second beam 82. The laser diode 42 and the coupling lenses 43 and 44 that convert the emitted beams of the laser diodes 41 and 42 into parallel light fluxes, respectively.
And a polarization beam splitter in which the respective beams from the coupling lenses 43 and 44 are incident on the planes orthogonal to each other, the first beam 81 is transmitted, the second beam 82 is reflected, and both beams are emitted in the same direction. 45, a deflector 48 for deflecting each beam from the polarization beam splitter 45, and a folding mirror 46 for making each beam from the polarization beam splitter 45 incident on a rotating polygon mirror of the deflector 48.
And a cylinder lens 47 which is provided between the folding mirror 46 and the deflector 48 and constitutes a part of an optical system for correcting the surface tilt of the rotary polygon mirror of the deflector 48.

The optical scanning device further scans between a scanning lens system 49 for forming an image of each beam deflected by the deflector 48 on the photoconductor 53, and between the scanning lens system 49 and the photoconductor 53. A cylinder mirror 50, a gap adjusting mirror 51, and a registration adjusting mirror 52 are provided in this order from the lens system 49 side. The cylinder mirror 50 constitutes a part of an optical system for correcting the surface tilt of the rotary polygon mirror of the deflector 48. The space adjusting mirror 51 is for adjusting the space between the two beams, and will be described in detail later. The registration adjustment mirror 52 is for adjusting the beam position on the photoconductor 53.

The optical scanning device further includes a pickup mirror 55 that reflects a beam of the beam deflected by the deflector 48 outside the scanning area on the scanning start end side.
A lens 56 and a photosensor 57 provided on the optical path of the reflected light of the mirror 55, and a pickup mirror 60 that reflects a beam outside the scanning region on the scanning end side of the beam deflected by the deflector 48. And a triangular slit 61 and a photo sensor 62 provided on the optical path of the reflected light of the mirror 60. The photo sensor 57 outputs a sync signal for controlling the writing position of the image. The triangular slit 61 and the photo sensor 62 are for detecting the distance between the two beams.

In this optical scanning device, the P-polarized first beam 81 emitted from the first laser diode 41 is used.
Is converted into a parallel light beam by the coupling lens 43 and transmitted through the polarization beam splitter 45. On the other hand, the S-polarized second beam 82 emitted from the second laser diode 42.
Are collimated by the coupling lens 44 and reflected at a right angle by the polarization beam splitter 45, and the first beam 8
Go in the same direction as 1. Each beam emitted from the polarization beam splitter 45 is reflected and deflected by a deflector 48 after passing through a folding mirror 46 and a cylinder lens 47, and a scanning lens system 49, a cylinder mirror 50, an interval adjustment mirror 51 and a registration adjustment mirror 52. Then, the photoconductor 53 is irradiated with the light. Further, by changing the angle of the spacing adjustment mirror 51 with respect to each incident beam, the spacing between the two beams emitted from the spacing adjustment mirror 51 in the sub-scanning direction, that is, the dot spacing in the sub-scanning direction is adjusted. Further, the dot position is corrected by the registration adjusting mirror 52 for the purpose of aligning the dots on the photoconductor 53 in the sub-scanning direction. When the distance adjusting mirror 51 is arranged near the photoconductor 53, the registration adjusting mirror 52 becomes unnecessary.

Next, the interval adjusting mirror 51 will be described in detail with reference to FIGS. 12 and 13. 12 is an explanatory view showing the vicinity of the space adjusting mirror 51, and FIG. 13 is a sectional view of the space adjusting mirror 51.

As shown in FIG. 12, the space adjusting mirror 51.
Is held by a bracket 65 which is rotatable around a fulcrum 66. The torsion spring 67 is in contact with one surface of the bracket 65, and the feed screw 68 is in contact with the other surface of the bracket 65. Then, by rotating the feed screw 68, the angles of the bracket 65 and the interval adjusting mirror 51 can be adjusted.

As shown in FIG. 13, the space adjusting mirror 51.
Is coated with a reflective layer 72 that reflects only S-polarized light on a flat glass plate 73, and a thin film layer 70 having a refractive index of about 1.5 to 1.7 is deposited on the reflective layer 72. A reflective layer 71 that reflects only light is coated.

As shown in FIG. 12, the space adjusting mirror 51
A P-polarized first beam 81 and an S-polarized second beam 8
When 2 and 2 are incident, the first beam 81 is reflected on the surface of the interval adjusting mirror 51, and the second beam 82 is reflected on the back surface of the interval adjusting mirror 51. Therefore, if the incident angle is not zero, the first beam 81 81 and the second beam 82 have a predetermined distance d.
Is emitted in parallel from the gap adjusting mirror 51. The distance d between the two beams changes depending on the angle of the distance adjusting mirror 51 with respect to the incident beam.

A feed screw 68 for rotating the bracket 65
Is rotated by a drive device (not shown). This driving device applies servo based on the beam interval detected by the photo sensor 62 so that the beam interval d has a desired value.

When three or more beams are used, the optical characteristics of each beam are made different and the space adjusting mirror 51 is used.
By forming a plurality of reflecting surfaces that selectively reflect each beam on the basis of the optical characteristics of each beam, the beam spacing can be adjusted in the same manner as in the case of two beams. FIG. 14 shows an example of the interval adjusting mirror 51 when three beams are used. The spacing adjusting mirror 51 shown in this figure has a reflecting surface 74 that reflects two other specific wavelengths, which are coded on a flat glass plate 75, and has a refractive index of 1.
A thin film layer 73 having a thickness of about 5 to 1.7 is attached, a reflecting surface 72 that reflects only S-polarized light is coated thereon, and a thin film layer 70 having a refractive index of about 1.5 to 1.7 is further formed thereon. A reflective surface 71 that adheres and that reflects only P-polarized light is coated thereon. The reflecting surfaces 71 and 72 are assumed to transmit the light of the specific wavelength reflected by the reflecting surface 74. When using the space adjusting mirror 51 shown in FIG. 14,
As the three beams, the first beam is a P-polarized beam of a specific wavelength reflected by the reflecting surface 71, and the second beam is the reflecting surface 71.
The S-polarized beam having a specific wavelength that is transmitted through the reflection surface 72 and is reflected by the reflection surface 72. The third beam is a specific wavelength beam having a wavelength different from the above, which is transmitted through the reflection surfaces 71 and 72 and reflected by the reflection surface 74.

Triangular slit 61 and photo sensor 62
Has the same configuration as the triangular slit 21 and the photo sensor 22 shown in FIGS. 7 and 8. However, in the first embodiment, two sets of triangular slits and photosensors are used, but in the present embodiment, one set of triangular slits 61 and photosensors 62 detects dot intervals. As in the case of the first embodiment, the photo sensor 62 outputs a pulse having a width corresponding to the position where the beam passes through the hole of the triangular slit 61. Therefore, the pulse width when passing the first beam is t
₁ and t ₂ is the pulse width when passing the second beam, t
_The beam interval can be known from _2- t ₁ . In this embodiment, when measuring the pulse widths t ₁ and t ₂ ,
Only one beam is emitted and measured separately.

Next, the sensitivity of changes in the angle of the interval adjusting mirror 51 and changes in the dot interval will be described.

For example, the space adjusting mirror 5 in FIG.
The thin film layer 70 of No. 1 has a thickness of 35.6 μm, the angle of incidence of the beam on the interval adjusting mirror 51 is 30 degrees, the distance from the fulcrum 66 of the bracket 65 to the contact point of the feed screw 68 is 30 mm, and the interval adjusting mirror 51 to the photosensitive member. Assuming that an optical system of 50 mm up to 53 is designed, the distance traveled by the feed screw 68 to rotate the interval adjusting mirror 51 once is 0.52 mm, the initial dot interval is 25 μm, and the interval adjustment pitch is 1. It is 1 μm. The amount of movement of the lead registration (beam irradiation position on the photoconductor 53) at this time is 1.75 m.
m. It goes without saying that the interval adjustment pitch can be made small or large by changing the above conditions.

As described above, according to the present embodiment, the dot spacing is adjusted by the spacing adjusting mirror 51 provided at the rear stage of the scanning lens system 49, so that the configuration behind the cylinder lens 47 is 2. The configuration is simple because the two beams are the same. Further, since both the two beams pass through the optical axis of the scanning lens system 49, it is possible to prevent the scanning line from bending.

Other functions and effects are similar to those of the first embodiment.

[0053]

As described above, according to the first aspect of the present invention, one dot is formed by a plurality of beams, and the distance between the plurality of light beams on the surface to be scanned in the sub-scanning direction is adjusted. Since the diameter of the dots in the sub-scanning direction is adjusted, there is an effect that the dot diameter in the sub-scanning direction can be arbitrarily changed with a simple configuration without changing the dot diameter in the main scanning direction. .

According to the second aspect of the present invention, the distance between the plurality of light beams is adjusted by the mirror provided between the imaging optical system and the surface to be scanned. Since a plurality of light beams can pass through the optical axis of the imaging optical system, there is an effect that it is possible to prevent the bending of the scanning line.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration up to a scanning lens system of an optical scanning device according to a first exemplary embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration after a deflector of the optical scanning device of FIG.

3 is an explanatory view showing an optical path of a first beam after a deflector of the optical scanning device of FIG.

4 is an explanatory diagram showing an optical path of a second beam after a deflector of the optical scanning device of FIG.

FIG. 5 is a characteristic diagram showing light intensity distributions of two beams on a photoconductor at a predetermined resolution.

6 is a characteristic diagram showing light intensity distributions of two beams on a photoconductor at a resolution different from that in FIG.

FIG. 7 is a plan view of a triangular slit and a photo sensor in FIG.

FIG. 8 is a side view of the triangular slit and the photo sensor of FIG.

9 is a waveform diagram showing an example of output pulses of the photo sensor of FIG.

FIG. 10 is an explanatory diagram showing the overall configuration of an optical scanning device according to a second embodiment of the present invention.

FIG. 11 is an explanatory diagram of the optical scanning device in FIG. 10 viewed from the axial direction of the photoconductor.

12 is an explanatory diagram showing the vicinity of a gap adjusting mirror in FIG.

13 is a cross-sectional view of the gap adjusting mirror in FIG.

14 is a cross-sectional view showing another example of the gap adjusting mirror in FIG.

FIG. 15 is an explanatory diagram showing a configuration of a conventional optical scanning device of a first example.

FIG. 16 is an explanatory diagram of the optical scanning device in FIG. 15 viewed from the axial direction of the photoconductor.

17 is a characteristic diagram showing a light output in the optical scanning device of FIG.

FIG. 18 is an explanatory diagram showing a schematic configuration of an optical scanning device of a second conventional example.

FIG. 19 is a characteristic diagram showing a light intensity distribution of an image formation spot on a photoconductor in the optical scanning device of FIG.

[Explanation of symbols]

1, 2 ... Laser diode, 9 ... Deflector, 10 ... Scanning lens system, 12 ... Dot spacing adjustment mirror, 16 ... Photoconductor

Claims (2)

[Claims] 1. A light source unit for generating a plurality of light beams, a deflector for deflecting each light beam from the light source unit to scan a surface to be scanned, and each light beam deflected by the deflector. An imaging optical system that forms one dot by converging in a close position on the surface to be scanned, and adjusting the interval in the sub-scanning direction of a plurality of light beams on the surface to be scanned, An optical scanning device comprising: an adjusting unit for adjusting a diameter. 2. The light source section generates a plurality of light beams having different optical characteristics, and the adjusting means is provided between the imaging optical system and a surface to be scanned, and the optical means Having a mirror including a plurality of reflecting surfaces for selectively reflecting each light beam on the basis of various characteristics, and changing the angle of the mirror with respect to each incident light beam, the spacing between the plurality of light beams emitted in the sub-scanning direction The optical scanning device according to claim 1, wherein