JP3222755B2 - Scanning optical 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 scanning optical device for scanning a light beam in a laser printer or the like.

[0002]

2. Description of the Related Art In a scanning optical device for high definition, an allowable range of inclination and curvature of an image forming surface of light emitted from the scanning optical device is stricter than that of a normal scanning optical device. Therefore, at the time of manufacture, it is common to assemble the scanning optical device as a single unit and then finely adjust the inclination and the like of the lens in the scanning optical device while measuring the inclination and curvature of the image forming surface.

More specifically, a scanning optical device emits a stationary beam (a beam that does not perform scanning), measures the beam diameter in the vicinity of the image plane with a dedicated measuring instrument, and moves the measuring instrument in the optical axis direction. By making measurements while
A position where the beam diameter is minimized, that is, an image forming position is obtained. Then, the inclination or curvature of the imaging plane is obtained from the data of the imaging positions measured at three points in the main scanning direction. Then, fine adjustment such as the inclination of the lens is performed so that the image forming plane becomes a designed plane. Therefore, this adjustment involves a large number of measurements and requires a large number of work steps.

[0004]

However, in a high-definition printer, the scanning optical system is arranged substantially on the same plane, and the photosensitive drum is arranged at a position separated by a predetermined amount in a direction perpendicular to this plane. Is common. That is, the image forming surface is formed at a position separated in a direction orthogonal to the scanning optical devices arranged on the substantially same surface. Therefore, a large number of measurements must be performed three-dimensionally on the scanning optical device, and there is a problem that work efficiency is poor. Further, in recent years, printers have tended to increase in size with an increase in screen size, and the scanning optical device has become even larger, resulting in a jig structure in which it is difficult to secure a work space for an operator.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scanning optical device which makes it possible to easily adjust the inclination of an image forming surface in the scanning optical device.

[0006]

According to a first aspect of the present invention, there is provided a scanning optical apparatus, comprising: a light source; a deflecting unit for scanning a beam emitted from the light source; A lens for converging the plurality of beams on the drawing surface, and a case for housing the light source, the deflecting unit, and the fθ lens, wherein the case has a first opening and a second opening. Formed in the second
Is provided on the surface of the case that intersects with the extension of the beam that has been deflected by the deflecting means and transmitted through the fθ lens, and on the surface of the case that is different from the surface on which the second opening is formed. The first opening is formed, and a mirror is inserted so that a beam deflected by the deflecting means and transmitted through the fθ lens can be retracted into an optical path toward the second opening. Sometimes, the beam transmitted through the fθ lens is reflected by the mirror toward the first aperture, and when the mirror is not inserted, the beam transmitted through the fθ lens enters the second aperture, and A beam transmitted through one of the first and second openings is incident on the drawing surface. With this configuration, since the adjustment operation can be performed using an opening different from the drawing opening, the adjustment operation can be performed even when the photosensitive drum and the scanning optical device have a three-dimensional arrangement. This can be easily performed. In particular, if the first opening is an opening for guiding a beam to the drawing surface and the second opening is an adjustment opening, the adjustment operation can be performed in substantially the same plane as the scanning optical device. . In this case, the mirror is removed during adjustment, and the mirror is attached during drawing (claims 2 and 3).

Here, the light source is a multi-beam light source for simultaneously emitting a plurality of beams, and the deflecting means includes:
The plurality of beams may be simultaneously deflected (claim 5). In this case, the light source is configured to include a plurality of semiconductor lasers, a plurality of optical fibers respectively transmitting beams emitted from the respective semiconductor lasers, and a fiber alignment block for aligning light emitting end faces of the plurality of optical fibers. (Claim 6).

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a scanning optical device according to the present invention will be described below. The scanning optical device shown as the embodiment is a multi-beam scanning optical device that simultaneously forms eight scanning lines by one scanning by simultaneously scanning eight laser beams. First, a schematic configuration of the entire apparatus will be described.

FIG. 1 is a perspective view showing an embodiment of the scanning optical device, and FIG. 2 is a side view showing the embodiment of the scanning optical device together with the photosensitive drum. As shown in FIG. 1, the scanning optical device is configured by disposing a scanning optical system in a substantially rectangular parallelepiped flat casing 1. The upper opening of the casing 1 is closed by the upper lid 2 during use.

In the upper part of the casing 1 in the figure, a connector part 102 for receiving a signal relating to image information is provided. A laser block support substrate 300 is provided adjacent to the connector 102. The support substrate 300 includes a laser block 310 that holds the eight semiconductor lasers 101 that emit light beams based on the signals and the input ends of the optical fibers 120, facing each other. Fixed. As a result, 8
A light beam is guided to the two optical fibers 120.

The end face 120 of the optical fiber 120 on the emission side
b is held by the fiber alignment block 130. The light beam from the exit end face 120b is transmitted to a collimating lens 140, a half mirror 144, a dynamic prism 160, and the cylindrical lens 1 described later.
The light is incident on the polygon mirror 180 via 70. The polygon mirror 180 is rotationally driven by a polygon motor 371 (see FIG. 2) fixed to the casing.
Reflects and deflects the light beam incident on the mirror surface. The light beam deflected by the polygon mirror 180 enters an fθ lens 190 that is an imaging lens. The light beam from the fθ lens 190 is reflected downward by the turning mirror 200 in the figure, and forms an image on the photosensitive drum 210 as a scanning target surface as shown in FIG.

Here, in order to define the operation of the optical element,
Fθ lens 190 and photosensitive drum 2 in a plane perpendicular to the optical axis.
The scanning direction of the light beam on 10 (FIG. 2) is defined as the main scanning direction, and the direction perpendicular to the main scanning direction in a plane perpendicular to the optical axis is defined as the sub-scanning direction. In the drawing, an X axis parallel to the optical axis of the fθ lens 190, and a Y axis and a Z axis orthogonal to each other in a plane perpendicular to the X axis are defined. The Y axis and the Z axis correspond to the main scanning direction and the sub scanning direction, respectively.

Next, each component of the optical system will be described with reference to FIG. The light source unit 100 includes eight semiconductor lasers 101, eight optical fibers 120 that transmit divergent light beams emitted from these semiconductor lasers, and a fiber alignment block 1 that linearly aligns these optical fibers 120.
30. The optical fiber 120 is a quartz glass fiber having a core diameter of 6 μm and an overall diameter including the cladding of 125 μm.

An end of the optical fiber 120 including the incident end face 120a is held by a fiber support 319 which is a support tube. The fiber support 319 is located at the input end 1.
The laser block 310 is held with the semiconductor laser 101 facing the semiconductor laser 20a. The light beam emitted from the semiconductor laser 101 is transmitted to the optical fiber 120.
Incident on the incident end face 120a.

As shown in FIG. 3, in the optical path between the light source unit 100 and the polygon mirror 180, a collimating lens 140 and a collimating lens 140 for converting a divergent light beam emitted from the exit end face of the optical fiber into a parallel light beam are emitted. A slit 142 for controlling the beam shape by a rectangular opening having sides in the main scanning direction and the sub-scanning direction of the light beam, a half mirror 144 for separating the light beam transmitted through the slit 142 into two, and a light beam reflected by the half mirror 144 Dynamic prism 160 that sequentially controls by rotating the angle in the sub-scanning direction, and dynamic prism 1
A cylindrical lens 170 that converges the light beam whose angle is controlled by 60 in the sub-scanning direction is provided.

The light beam transmitted through the half mirror 144 is incident on an APC (automatic power control) signal detector 150 for detecting a light amount and obtaining a signal for controlling the output of the semiconductor laser. The APC signal detection section 150 converges the light beam transmitted through the half mirror 144 by the condenser lens 151 and makes the light beam enter the polarization beam splitter 153. Polarizing beam splitter 1
Reference numeral 53 separates the incident light beam into transmitted light that is transmitted in the incident direction and polarized light that is polarized in a direction orthogonal to the incident direction. The transmitted light is detected by the first light receiving element 155 for APC, and the polarized light is detected by the second light receiving element 157 for APC.

The exit end face 120b of the fiber 120 is
Fiber alignment block 130 and fiber alignment block holder 300 (not shown) to be described later.
As shown in FIG. 4, they are arranged at predetermined intervals on a straight line inclined at a predetermined angle with respect to the main scanning direction to form a point light source array. In FIG. 3, the light flux from the point light source array composed of the eight point light sources passes through the collimator lens 140, the cylindrical lens 170, and the like, and
An image is formed in the sub-scanning direction near the 0 mirror surface. The light beam incident on the polygon mirror 180 is scanned in the Y direction by the rotation of the polygon mirror 180, and is incident on the fθ lens 190.

Lens 190 is a polygon mirror 18
From the 0 side to the folding mirror 200 side, in the order of the main scanning direction and the sub scanning direction, negative, positive,
It comprises first, second, third, and fourth lenses 191, 193, 195, and 197 having positive and negative powers.
The light beam transmitted through the fθ lens 190 is reflected by the folding mirror 20.
0, an image is formed on the surface of the photosensitive drum 210 (FIG. 2), and the scanning speed in the main scanning direction becomes constant. In this way, the light beams from the eight point light sources form a row of beam spots as shown in FIG. 5 on the image plane. The photosensitive drum 210 is driven to rotate in the direction of arrow R in synchronization with scanning,
Thus, an electrostatic latent image is formed on the surface of the photosensitive drum 210.

Next, an embodiment of the scanning optical device of the present invention will be described. As shown in FIG. 2, a drawing opening 11 which is a first opening is provided on the bottom surface of the casing 1.
An adjustment opening 12 as a second opening is provided on a side surface of the casing 1 (a surface intersecting with the optical axis of the fθ lens 190). The drawing aperture 11 is for guiding the light emitted from the fθ lens 190, which is an image forming lens, reflected by the return mirror 200 to the surface of the photosensitive drum 210, which is an image forming surface. Therefore, the drawing opening 11
Has a rectangular shape having sides longer than the scanning range in the main scanning direction and the sub-scanning direction so that light emitted from the fθ lens 190 can pass therethrough. Also, the mirror 200
Is detachable from the casing 1.

The adjustment opening 12, like the drawing opening 11, has a rectangular shape having sides longer than the scanning ranges in the main scanning direction and the sub-scanning direction. In addition, adjustment opening 1
2 is the fθ lens 19 with the mirror 200 removed.
It is positioned in the optical axis direction of the fθ lens 190 so that light emitted from 0 (a light beam deflected by the polygon mirror 180 and transmitted through the fθ lens 190) can be transmitted. In addition, the adjustment opening 12 is provided with a lid 13 for preventing dust from entering the inside of the casing 1. Lid 13
Is screwed to the casing 1 so as not to easily come off.

FIG. 6 shows the scanning optical device at the time of adjustment. At the time of adjustment, the scanning optical device is attached to the base frame 410. The base frame 410 is provided with legs 411 for supporting the casing 1 of the scanning optical device, whereby the scanning optical device is horizontally supported. Adjustment opening 1
2 has sides longer than the scanning range in the main scanning direction and the sub-scanning direction.
The transmitted light from the lens 190 is guided to the outside of the casing 1. That is, the transmitted light from the fθ lens 190 passes through the adjustment opening 12 and is substantially in the same plane as the scanning optical device 1, in other words, between the lower surface of the casing 1 and the surface of the upper cover 2 extended respectively. Be guided.

The base frame 410 is provided with a measuring device 400 for measuring the beam diameter in the optical axis direction of the light emitted from the adjusting aperture 12 of the scanning optical device. Measuring instrument 4
Reference numeral 00 is provided with a light receiving surface at its tip, and measures the beam diameter within the light receiving surface.

The measuring device 400 is held by a base frame 410. A unit frame 420, which is a plate member fixed to the base frame 410, has a main scanning direction (Y direction: a direction perpendicular to the plane of FIG. 6). A pair of extended guide rails 422 is provided. A nut 423 is movably engaged on each of the guide rails 422, and a table 425 is fixed to the nut 423. A guide rail 426 extending in the optical axis direction (X direction) is formed on the table 425.
, A nut 427 is movably engaged. And
A holding plate 430 holding the measuring device 400 is fixed to the nut 427. Thus, the measuring device 40
0 is movable in the main scanning direction (Y direction) and the optical axis direction (X direction).

Next, an outline of the fine adjustment of the optical system using the adjustment aperture 12 will be described with reference to FIG. At the time of manufacturing the scanning optical device, the scanning optical device is assembled as a single unit, and fine adjustment of the inclination and the like of the lens in the scanning optical device is performed while measuring the inclination and curvature of the imaging surface. At this time, the polygon 180 (FIG. 6) is stopped, and a single beam is emitted as emission light. The single beam passes through the aperture 12 and forms a stationary beam spot on the image plane F as shown in FIG.

The beam diameter is measured at several points in the direction of the optical axis X by the measuring device 400, and the position where the beam diameter becomes minimum is the beam waist position, that is, the image forming position. Such measurement of the image forming position is further performed at several places in the main scanning direction (the central portion A and both end portions B and C in the main scanning direction in FIG. 7). Then, the inclination or curvature of the imaging plane is calculated from the data of the imaging positions defined at several places in the main scanning direction.

That is, for example, in FIG. 7, when the image forming position that should be point B is point B ′ and the image forming position that should be point C is point C ′, the image plane F becomes It can be seen that it is inclined (or rotated) in the direction D in the figure.
In such a case, the fθ lens 190 is moved until the imaging position at the point B ′ or C ′ moves to the point B or C ′, respectively.
Fine adjustment such as adjustment of the inclination of the appropriate lens inside is performed.

As described above, according to the scanning optical system of the present embodiment, positioning for moving the measuring instrument 400 with high accuracy in the optical axis X direction and the main scanning direction Y is performed in substantially the same plane as the scanning optical device. Can be done with For this reason, the adjustment operation becomes extremely easy as compared with the conventional one in which the measurement device is adjusted three-dimensionally below the scanning optical device 1.

As described above, according to the scanning optical apparatus of the present invention, the emitted light can be guided to the measuring instrument from the adjusting aperture provided separately from the drawing aperture, so that the adjusting operation can be easily performed. It can be carried out. In particular, if the surface of the casing (the second opening) that intersects with the optical axis of the fθ lens is set as the opening for adjustment, the surface is substantially in the same plane as the scanning optical device (in the plane in which the upper and lower surfaces of the casing are extended). Since the light beam is guided, the positioning of the measuring instrument can be performed in substantially the same plane as the scanning optical device, and the adjustment operation can be performed extremely easily.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a scanning optical device according to the present invention.

FIG. 2 is a side view of the scanning optical device of FIG.

FIG. 3 is a diagram illustrating an optical system of the scanning optical device in FIG. 1;

FIG. 4 is a diagram showing a point light source array.

FIG. 5 is a diagram showing a beam spot.

FIG. 6 is a side view showing the scanning optical device at the time of adjustment.

FIG. 7 is a perspective view showing an image forming plane.

[Explanation of symbols]

 Reference Signs List 1 casing (case) 2 lid 11 drawing opening (one opening) 12 adjustment opening (the other opening) 13 lid 100 light source unit 120 fiber 140 collimating lens 180 polygon mirror 190 fθ lens 200 folding mirror 210 photosensitive drum 400 Measuring instrument 410 Base frame

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsunori Iima 2-36-9 Maenocho, Itabashi-ku, Tokyo Asahi Optical Industry Co., Ltd. (56) References JP-A-8-82759 (JP, A) ( 58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 26/10

Claims (6)

(57) [Claims] A light source; a deflecting unit for scanning a beam emitted from the light source; an fθ lens for converging the plurality of beams deflected by the deflecting unit on a drawing surface; And a case for storing the fθ lens. The case has a first opening and a second opening, and the second opening is deflected by the deflecting means.
the first opening is formed on a surface of the case that intersects with an extension of the beam transmitted through the θ lens, and the first opening is formed on a surface of the case different from the surface on which the second opening is formed; A mirror deflected by the means and transmitted through the fθ lens is inserted into the optical path toward the second opening so that a mirror can be retracted. When the mirror is inserted, the beam transmitted through the fθ lens is A beam reflected by the mirror toward the first opening and transmitted through the fθ lens when the mirror is not inserted is incident on the second opening, and one of the first and second openings is A beam transmitted through an aperture is incident on the drawing surface. 2. The scanning optical system according to claim 1, wherein the first opening is an opening for guiding a beam to the drawing surface, and the second opening is an adjustment opening. apparatus. 3. The scanning optical device according to claim 2, wherein the mirror is removed during adjustment. 4. The scanning optical device according to claim 2, wherein the mirror is attached at the time of drawing. 5. The light source according to claim 1, wherein the light source is a multi-beam light source that emits a plurality of beams simultaneously, and the deflecting unit deflects the plurality of beams simultaneously. A scanning optical device according to any one of the above. 6. The light source includes a plurality of semiconductor lasers, a plurality of optical fibers respectively transmitting beams emitted from the respective semiconductor lasers, and a fiber alignment block for aligning light emitting end faces of the plurality of optical fibers. The scanning optical device according to claim 5, wherein: