JP2002244058A - Laser beam scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam scanner which makes it possible to obtain good scanning at a low cost in spite of use of scanning interval regulating means. SOLUTION: This laser beam scanner has a semiconductor array 1 which has plural light emitting points, a polygon mirror (deflecting means) 5 which deflects the laser beam emitted from the semiconductor array 1, an optical system which scans the surface of an object to be scanned by imaging the laser beam deflected by the polygon mirror 5 to this surface and a prism unit 3 (scanning interval regulating means) which is arranged on the optical path on the incident side of the polygon mirror 5 and regulates the scanning intervals on the surface of the object to be scanned. A parallel flat plate (optical path correcting means) 101 for correcting the shift of the optical axis by the prism unit 3 is disposed between the prism unit 3 and the polygon mirror 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser array having a plurality of light emitting points, deflecting means for deflecting laser light emitted from the semiconductor laser array, and scanning the laser light deflected by the deflecting means. A laser beam scanning apparatus comprising: an optical system that forms an image on a surface of an object and scans the light; Related to the device.

[0002]

2. Description of the Related Art In recent years, a laser beam scanning device using a semiconductor laser array having a plurality of light emitting points has appeared as one means for increasing the speed of the laser beam scanning device.

In such a laser beam scanning device,
Some include a scanning interval adjusting unit that changes an opening angle of a plurality of laser beams and adjusts a scanning interval on a surface of an object to be scanned. FIG. 5 shows an example of a laser beam scanning device having a scanning interval adjusting means.

In FIG. 1, a semiconductor laser array 1 has a plurality of laser emission points. The number of laser emission points of the semiconductor laser array 1 is a predetermined integer of 2 or more,
These laser emission points are arranged in a line in the sub-scanning direction on the laser beam path. The plurality of laser beams emitted from the semiconductor laser array 1 are diffused beams.

The laser light path is refracted and reflected by the collimator lens 2, the prism unit 3, the polygon mirror 5, the cylinder mirror 8, and the like. However, when the laser light path is expressed in a straight line as shown in FIG. The main scanning direction (main scanning direction) is referred to as “main scanning direction on the laser beam path”, and the sub-scanning direction is referred to as “sub-scanning direction on the laser beam path”.

The collimator lens 2 converts a plurality of laser beams emitted from the semiconductor laser array 1 into a parallel beam,
The beam shape is shaped into a predetermined shape. However, the plurality of laser beams converted into parallel light beams by the collimator lens 2 are not parallel to each other, and have an opening angle between the plurality of laser beams. The at least one laser beam is not parallel to the laser optical axis.

A prism unit 3, which is a scanning interval adjusting means provided removably on the optical path of the laser beam emitted from the collimator lens 2, converts a plurality of laser beams incident from the collimator lens 2 to a plurality of prisms. By passing the laser light, the opening angle between the plurality of laser lights is converted into a predetermined opening angle, and the plurality of laser lights are emitted.

The cylindrical lens 4 has a refractive power only in the sub-scanning direction on the laser beam path, and forms a plurality of laser beams emitted from the prism unit 3 into a linear image on the surface of the polygon mirror 5. .

A slit 41 for adjusting the width of the laser beam in the main scanning direction is provided between the prism unit 3 and the cylindrical lens 4. The polygon mirror 5 serving as a deflecting unit is rotated at a constant speed by a polygon mirror driving motor 9, and is rotated at a constant speed.
Are deflected at a predetermined angular velocity in the main scanning direction.

Next, an optical system for forming an image of the laser beam deflected by the deflecting means on the surface of the object to be scanned and scanning the object will be described. The first fθ lens 6 and the second fθ lens 7
A plurality of laser beams having the θ characteristic and deflected at a constant angular velocity by the polygon mirror 5 are scanned at a constant main scanning speed on the photosensitive member on the surface layer of the photosensitive drum 40 which is an object to be scanned. Convert.

The cylinder mirror 8 is a mirror having an image forming power only in the sub-scanning direction on the laser beam path, corrects the tilt angle of the polygon mirror 5, and forms an image on the polygon mirror 5 and reflects the image. The plurality of laser beams that have passed through the first fθ lens 6 and the second fθ lens 7 form images at different positions on the surface of the photosensitive drum 40 in the sub-scanning direction.

A plurality of laser beams, which form images at different positions in the sub-scanning direction on the surface of the photoconductor drum 40, scan the photoconductor on the surface layer of the photoconductor drum 40 at a constant main scanning speed. Then, a latent image is formed on the photoconductor on the surface layer of the photoconductor drum 40.

The photosensitive drum 40 has a photosensitive layer on its surface and has a drum-like shape having a central axis in the main scanning direction on the laser beam path, and is held so as to be rotatable about the central axis. I have. When the photosensitive drum drive motor 20 rotates at a constant speed, the pinion 21 fitted on the motor shaft of the photosensitive drum drive motor 20 rotates at a constant speed, and is attached to the photosensitive drum 40 that meshes with the pinion 21. When the cylindrical gear 22 rotates at a constant speed, the photosensitive drum 40 rotates at a constant speed.

The toner developing unit 60 is provided at a position downstream of the surface of the photosensitive drum 40 where a plurality of laser beams form images on the photosensitive member in the rotation direction of the photosensitive drum 40. The latent image formed on the photoconductor is developed with toner. Then, the transfer unit 70 is
0 is provided downstream of the photosensitive drum 40 in the rotation direction of the photosensitive drum 40,
The toner image formed on the surface of the photosensitive drum 40 by the toner developing device 60 is transferred to a transfer sheet. The transfer paper is then separated and sent to a fixing device (not shown). Then, the fixing device fixes the toner image transferred to the transfer paper.

The toner collecting unit 80 collects the remaining toner on the surface of the photosensitive drum 40 that has not been transferred by the transfer unit 70. And the charger 90 is
The residual toner is recovered by the toner recovery unit 80, and the surface of the photoconductor drum of the cleaned photoconductor drum 40 is charged, so that a latent image is formed by exposure to laser light.

Next, a plurality of laser beams will be described in detail with reference to FIG. 6, which is an explanatory diagram of a laser beam path expressing a laser beam path on a straight line. The semiconductor laser array 1 is provided with two firing points in the sub-scanning direction, that is, a first light emitting point 11 and a second light emitting point 12.

The collimator lens 2 converts the two divergent laser beams L1 and L2 emitted from the first and second firing points into parallel luminous fluxes, respectively. However, the laser beams L1 and L2 are not parallel to each other but have an opening angle. have.

The angle δ1, which the two laser beams L1 and L2 emitted from the collimator lens 2 make with the optical axis L of the optical system,
δ2 is determined by the following equation by the focal length f2 of the collimator lens 2 and the positions s1 and s2 of the first laser emission point 11 and the second laser emission point 12 with respect to the laser optical axis L.

Δ1 = −tan ⁻¹ (s1 / f2) δ2 = −tan ⁻¹ (s2 / f2) The opening angle between the two laser beams L1 and L2 emitted from the collimator lens 2 is (δ1 −δ2).

Here, a prism unit 3 serving as a scanning interval adjusting means provided removably on the optical path of the laser light emitted from the collimator lens 2 is arranged on the optical path. The prism unit 3 includes a first prism 31 and a second prism 32.
Through the two laser beams L1 and L2,
The opening angles of the laser beams L1 and L2 are as follows. Therefore, when the prism unit 3 is provided on the optical path, the opening angle is increased by (γ1−γ2) as compared with the case where the prism unit 3 is not provided, the scanning interval on the surface of the photosensitive drum 40 which is the object to be scanned is widened, and The low-resolution mode is set as compared with the case where the prism unit 3 is not arranged.

[0021]

However, if the prism unit 3 is used in the above configuration, the laser light L1
When L2 passes through the prism unit 3, the optical axis shifts from the optical axis of the optical system (L → L ′ in FIG. 6).

In order to suppress this effect, a sufficiently large optical system is required for the shift of the optical axis of the laser beam, and the cost increases. When an ordinary optical system is used, good scanning cannot be obtained because the scanning interval and the beam diameter become non-uniform.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a laser beam scanning device which can obtain good scanning at low cost even when using a scanning interval adjusting means (prism unit 3). Is to provide.

[0024]

According to a first aspect of the present invention, there is provided a semiconductor laser array having a plurality of light emitting points, a deflecting means for deflecting a laser beam emitted from the semiconductor laser array, An optical system that forms an image of the laser beam deflected by the deflecting means on the surface of the object to be scanned and performs scanning;
A scanning interval adjusting unit arranged on an optical path on the incident side of the deflecting unit, and adjusting a scanning interval on the surface of the object to be scanned;
Wherein the optical path correcting means for correcting the shift of the optical axis by the scanning interval adjusting means is provided between the scanning interval adjusting means and the deflecting means. It is. By providing an optical path correction unit for correcting a shift of the optical axis by the scanning interval adjusting unit between the scanning interval adjusting unit and the deflecting unit, it is possible to prevent the scanning interval and the beam diameter from becoming non-uniform. And good scanning can be obtained.

According to a second aspect of the present invention, there is provided a laser beam scanning apparatus, wherein the optical path correcting means is a single parallel flat plate. When the laser light passes through the parallel flat plate, the laser light is refracted, and the optical axis shifted by the optical path correction means returns to the original optical axis, thereby preventing the scanning interval and the beam diameter from becoming non-uniform, thereby achieving good scanning. Is obtained.

Further, since the optical path correcting means is a parallel plate, the cost is low. The invention described in claim 3 is the invention according to claim 1.
The scanning interval adjusting unit and the optical path correcting unit according to the invention described above each include a pair of prism units, and the optical path correcting unit includes the scanning interval adjusting unit and the scanning interval adjusting unit with respect to a virtual axis orthogonal to an optical axis. A laser beam scanning device characterized by being symmetrically arranged.

The scanning interval adjusting means and the optical path correcting means each comprise a pair of prism units, and the optical path correcting means is symmetric with the scanning interval adjusting means with respect to a virtual axis orthogonal to the optical axis. By the arrangement of the prism unit of the scanning interval adjustment means and the prism unit of the optical path correction means, the entrance surface and the emission surface are switched,
The optical axis shifted by the scanning interval adjusting means is returned to the original optical axis by the optical path correcting means, so that the scanning interval and the beam diameter are prevented from becoming non-uniform, and good scanning can be obtained.

Further, since the optical path correcting means is a set of two prism units, the cost is low. According to a fourth aspect of the present invention, the optical path correcting unit according to any one of the first to third aspects is provided immediately after the scanning interval correcting unit. ,
A laser light scanning device, which is integrally insertable into and removable from the optical path.

The optical path correcting means is provided immediately after the scanning interval correcting means, and the scanning interval correcting means and the optical path correcting means can be integrally inserted into and removed from the optical path. The configuration is simplified.

In this specification, a laser beam scanning device is a device for scanning an object to be scanned with a laser beam.
Used as an image forming apparatus in which an object to be scanned is an image forming body on which an image is formed by exposure to laser light, and also used as an inspection apparatus in which an object to be scanned is an object to be inspected by scanning with laser light. Or may be used in other forms.

Further, the prism is a prism made of a medium having a refractive index different from that of the atmosphere, and has a plane of incidence and a plane of exit, and the plane of incidence and the plane of exit are crossed. However, the present invention is not limited to this, and may be a trapezoidal pillar, a fan-shaped pillar, a quadrangular pyramid, or the like.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) First Embodiment A first embodiment will be described with reference to FIG. The same parts as those in FIGS. 5 and 6 for explaining the conventional example are denoted by the same reference numerals, and overlapping description will be omitted.

In the figure, reference numeral 101 denotes a parallel plate as an optical path correcting means provided between the prism unit 3 as a scanning interval adjusting means and the polygon mirror 5 as a deflecting means.

In the present embodiment, the parallel flat plate 101 is provided immediately after the prism unit 3 and is provided together with the prism unit 3 so as to be insertable into and removable from the optical path of laser light.
That is, the portion surrounded by the two-dot chain line in FIG. 1 can be inserted into and removed from the optical path of the laser light.

Next, referring to FIG.
Optical path correction when 01 is provided will be described. Parallel plate 10
The shift amount δ of the light ray by 1 is generally expressed by the following equation.

Here, the refractive index of the parallel flat plate 101 with respect to vacuum is n, the thickness is t, the inclination angle (incident angle) is θ, and the refraction angle is θ2. θ2 = sin ⁻¹ (1 / n × sinθ) δ = t × sin (θ−θ2) / cosθ2 As an example, as shown in FIG. 2, the vertex angles α1 = α2 of the first and second prisms 31 and 32. = 27.1 °, the angle β between the entrance surfaces of the first prism 31 and the second prism 32 =
16.40 °, refractive index n = 1.
51072.

In such a case, the beam shift amount is set at 2.
7 mm. Here, t behind the prism unit 3
By arranging a parallel plate of = 8 mm at an inclination angle θ = 45 °, the shifted optical path can be made closer to the vicinity of the optical axis of the optical system.

Of course, the beam shift amount changes depending on the positional relationship between the first prism 31 and the second prism 32, but the shift of the optical path can be reduced by optimizing the thickness t and the inclination angle θ of the parallel flat plate 101. Can be corrected.

According to the above configuration, the laser beam is emitted from the parallel flat plate 1.
When the light passes through 01, the laser light is refracted, and the optical axis shifted by the prism unit 3 (optical path correcting means) returns to the original optical axis. A scan is obtained.

Since the optical path correcting means is a parallel flat plate 101, the cost is low. (2) Second Embodiment The second embodiment will be described with reference to FIG. The same parts as those in FIGS. 5 and 6 for explaining the conventional example are denoted by the same reference numerals, and overlapping description will be omitted.

In the figure, reference numeral 3 'denotes a prism unit as an optical path correcting means provided between the prism unit 3 as the scanning interval adjusting means and the polygon mirror 5 as the deflecting means.

In this embodiment, the prism unit 3 ′ is provided immediately after the prism unit 3, and is provided on the optical path of the laser light together with the prism unit 3 so as to be insertable and removable. That is, the portion surrounded by the two-dot chain line in FIG. 3 can be inserted into and removed from the optical path of the laser light.

As shown in FIG. 4, the prism unit 3 'includes a first prism 31' and a second prism 3 '.
2 ′, and are disposed symmetrically with the prism unit 3 with respect to a virtual axis J orthogonal to the optical axis L.

Therefore, the entrance surface and the exit surface of the prism unit 3 and the prism unit 3 'are switched, and the optical path shifted by the prism unit 3 is corrected to the optical axis L of the optical system by the prism unit 3', and the scanning interval and beam Non-uniform diameter is prevented, and good scanning is obtained.

In this case, however, the apex angle of the prisms and the angle between the incident surfaces of the two prisms are set so that the angles formed by the plurality of laser beams after passing through the pair of prisms have a desired value. There is a need to.

Since the prism unit 3 'as the optical path correcting means is a set of two prism units,
Low cost.

[0047]

As described above, according to the first aspect of the present invention, the optical path correction for correcting the shift of the optical axis by the scanning interval adjusting means is provided between the scanning interval adjusting means and the deflecting means. By providing the means, it is possible to prevent the scanning interval and the beam diameter from becoming non-uniform, thereby obtaining good scanning.

According to the second aspect of the invention, when the laser beam passes through the parallel flat plate, the laser beam is refracted, and the optical axis shifted by the optical path correcting means returns to the original optical axis, and the scanning interval and beam diameter are changed. Is prevented from becoming non-uniform, and good scanning can be obtained.

Further, since the optical path correcting means is a parallel plate, the cost is low. According to the invention described in claim 3,
The scanning interval adjusting unit and the optical path correcting unit each include a pair of prism units, and the optical path correcting unit is disposed symmetrically with the scanning interval adjusting unit with respect to a virtual axis orthogonal to the optical axis. Accordingly, the incident surface and the emission surface are switched between the prism unit of the scanning interval adjusting unit and the prism unit of the optical path correcting unit, and the optical axis shifted by the scanning interval adjusting unit returns to the original optical axis in the optical path correcting unit. In addition, it is possible to prevent the scanning interval and the beam diameter from becoming non-uniform, thereby obtaining good scanning.

Further, since the optical path correcting means is a set of two prism units, the cost is low. According to the fourth aspect of the present invention, the optical path correcting unit is provided immediately after the scanning interval correcting unit, and the scanning interval correcting unit and the optical path correcting unit are integrally inserted into the optical path. Removability simplifies the configuration.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an inventive portion of a first embodiment.

FIG. 2 is a diagram illustrating an optical path correction unit in FIG. 1;

FIG. 3 is a configuration diagram showing an inventive portion of a second embodiment.

FIG. 4 is a diagram illustrating an optical path correction unit in FIG. 3;

FIG. 5 is a configuration diagram showing an example of a laser beam scanning device having a conventional scanning interval adjusting unit.

FIG. 6 is an explanatory diagram of a laser light path expressing the laser light path of FIG. 5 on a straight line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser array 3 Prism unit 5 Polygon mirror (deflection means) 100 Parallel plate (optical path correction means)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C362 AA47 AA49 BA58 BA60 BA61 BA82 BA84 DA08 2H045 AA01 BA23 BA33 CA03 DA02 5C051 AA02 CA07 DA02 DB02 DB22 DB24 DB30 DC04 DC07 DE07 5C072 AA03 BA01 BA02 DA02 DA04 DA10 DA20 HA21 HA02 HA13

Claims (4)

[Claims] A semiconductor laser array having a plurality of light emitting points; a deflecting means for deflecting laser light emitted from the semiconductor laser array; and an image of the laser light deflected by the deflecting means on a surface of an object to be scanned. And an optical system that performs scanning, a scanning interval adjusting unit that is disposed on an optical path on the incident side of the deflecting unit and adjusts a scanning interval on the surface of the object to be scanned.
A laser beam scanning device, comprising: an optical path correcting unit that corrects a shift of an optical axis caused by the scanning interval adjusting unit between the scanning interval adjusting unit and the deflecting unit. . 2. The laser beam scanning device according to claim 1, wherein said optical path correction means is a single parallel flat plate. 3. The scanning interval adjusting unit and the optical path correcting unit each include a pair of prism units, and the optical path correcting unit is configured to move a virtual axis perpendicular to an optical axis.
2. The laser beam scanning device according to claim 1, wherein the laser beam scanning device is arranged symmetrically with the scanning interval adjusting unit. 4. The optical path correcting unit is provided immediately after the scanning interval correcting unit, and the scanning interval correcting unit and the optical path correcting unit can be integrally inserted into and removed from the optical path. The laser beam scanning device according to claim 1, wherein: