JPH0682717A - Light scanning device - Google Patents

Abstract

PURPOSE:To perform a plurality of times of scanning at one rotation and eliminate variation of a deflecting point due to rotation of a reflecting body so as to perform correct deflecting scanning. CONSTITUTION:A light emitting unit 22 and a reflecting mirror 23 to project a light flux in parallel with a rotary shaft is provided over the rotary shaft 12b of a scanner motor 12, a scanning mirror 17 which is positioned on the rotary shaft 12b of the motor 12 and driven to rotate with the motor is provided, and the scanning mirror 17 is formed with prisms 171, 172 having two semipermeable first reflecting faces which are mutually opposed to each other at an angle of 90 deg. and have equal inclination, and having second reflecting faces which are meeted with the respective first reflecting faces at an angle of 90 deg. and reflect the light flux transmitted through the corresponding first reflecting faces in the reverse direction against the reflecting direction of the light flux at the first reflecting faces.

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 laser printers, laser fax machines, digital copying machines and the like.

[0002]

2. Description of the Related Art For example, in a laser printer, recording information is placed on a laser beam from a semiconductor laser, and the laser beam is deflected and scanned by an optical system to be focused on a charged photoconductor surface which is an image forming surface. The body is exposed to record the record information on the photoreceptor as an electrostatic latent image. The electrostatic latent image is then developed with toner and then transferred to a sheet at the transfer section. That is, printing is performed by the electrophotographic developing method.

In such an apparatus, the exposure of the photosensitive member is performed by a digital exposure method, and the digital exposure method is LE.
A method using a solid-state device such as D, LCD, and EEH, and a method of rotating a polygon mirror or a hologram to deflect and scan a laser beam are known. At present, the digital exposure method using a polygon mirror is the mainstream.

However, in the case where the polygon mirror is used, a dedicated processing machine is required for cutting the polygon mirror, the required accuracy becomes extremely high, and the surface error occurs due to the processing error of each reflecting surface. Since the fθ lens and the cylindrical lens must be arranged to correct the surface tilt, and the reflection mirror and the cylindrical lens are arranged near the photosensitive drum, the cost becomes high and the configuration becomes complicated and large-sized. There was a problem to do.

Therefore, an optical scanning device that does not use a polygon mirror has been developed. As such a thing, the thing shown in Unexamined-Japanese-Patent No. 1-131513 is known.
As shown in FIG. 7, a deflector 1 is provided with a pyramidal mirror 2 rotatably, and the pyramidal mirror 2 is surrounded by a cylindrical slit member 3. A circular slit 4 is provided at the bottom of the slit member 3, and a rectangular slit 5 is provided at a portion of the peripheral surface facing the reflection surface of the pyramidal mirror 2. Then, the laser light L is made incident through the circular slit 4 of the deflector 1, reflected by the reflection surface of the pyramidal mirror 2, and the reflected light is emitted as scanning light from the rectangular slit 5.

[0006]

However, in the case of this publication, since the pyramidal mirror 2 has one reflecting surface, only one scan can be performed in one rotation. For example, this optical scanning device is applied to a laser printer. In this case, when the printing speed is 4PPM (pages / minute), the rotation speed of the motor is about 20,000r.
It is also pm, which is difficult to realize without using expensive elements such as a dynamic pressure bearing.

Therefore, the present invention is intended to provide an optical scanning device which can perform scanning a plurality of times with one rotation, and can perform accurate deflection scanning without changing a deflection point due to rotation of a reflector. .

[0008]

The invention according to claim 1 is
A motor for rotationally driving a rotor attached to the rotary shaft,
This motor comprises means for making a light beam parallel to the rotation axis of the motor incident on the rotation axis of the motor, and a scanning mirror provided on the rotation axis of the motor and rotationally driven by the motor.
As the scanning mirror, one having an even number of semi-transmissive reflective surfaces having the same inclination angle opposed to each other at an angle of 90 ° was used, and the scanning mirror was installed so that the center of the light beam was incident on the boundary of each semi-transmissive reflective surface. It is a thing.

According to a second aspect of the present invention, the scanning mirror has even-numbered semi-transmissive first reflecting surfaces facing each other at an angle of 90 ° and having equal inclination angles, and the angles formed by the respective first reflecting surfaces are equal to each other. The one having a second reflecting surface that reflects the light beam transmitted through the corresponding first reflecting surface at 90 ° in the direction opposite to the direction of reflection of the light beam by the first reflecting surface is used, and the boundary of each first reflecting surface is used. It is installed so that the approximate center of the luminous flux is incident.

[0010]

According to the first aspect of the invention, when a light beam parallel to the rotation axis of the motor is incident on the rotation axis of the motor, the substantially center of the light ray is incident on the boundary of each semi-transmissive reflection surface of the scanning mirror. Become so. As a result, the light beam is split and reflected by each semi-transmissive reflecting surface. Then, one of the reflected lights is transmitted as the deflected scanning light through the opposing semi-transmissive reflective surface and is emitted. Such deflection scanning light is generated by the number of semi-transmissive reflective surfaces during one rotation of the motor.

In the invention according to claim 2, the incident light beam is divided and reflected by each first reflecting surface, and a part of the divided light beam is transmitted through the first reflecting surface to correspond to the first reflecting surface. The two reflecting surfaces reflect light in a direction opposite to the direction of reflection by the first reflecting surface. Then, one of the reflected lights on each of the first reflecting surfaces is emitted as deflective scanning light through the opposing first reflecting surface and is also emitted from the second reflecting surface corresponding to the facing first reflecting surface. It is emitted as polarized scanning light. That is, the reflected light from the first reflecting surface and the reflected light from the second reflecting surface are combined and emitted as deflection scanning light.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view, and FIG. 2 is a plan view in which a cover member described later is omitted. Reference numeral 11 is a housing having a substantially rectangular shape and a cylindrical portion 11a formed in the center. The housing 11 is a scanner motor. Forming 12 stator members,
A bearing 13 composed of a ball bearing is provided in the cylindrical portion 11a of the housing 11. And the bearing 1
3 includes a rotary shaft 12b of the rotor 12a of the scanner motor 12
Is rotatably supported.

In the scanner motor 12, a magnet 12c is integrally attached to a rotor 12a, and the housing 1
A circuit board 15 is fixed to 1 via a spacer 14,
A coil 16 is attached to the back side of the portion of the circuit board 15 facing the magnet 12c.

A scanning mirror 17 is fixed on the rotor 12a of the scanner motor 12 on the rotary shaft 12b.

A cover member 18 is provided on the housing 11 so as to surround the scanner motor 12 and the scanning mirror 17.

As shown in FIG. 4, a light emitting unit 22 in which a semiconductor laser oscillator 19, a converging lens 20 and a slit 21 are integrally housed is screwed to the back surface of the cover member 18 so as to be detachable from the outside. There is.

The cover member 18 has an inclined surface facing the emitting portion of the laser beam from the light emitting unit 22, and a reflection mirror 23 is embedded in the inclined surface to emit the laser beam from the light emitting unit 22. Reflection mirror 23
A light beam that is reflected by and is parallel to the rotation axis 12b of the scanner motor 12 is applied from directly above the central portion of the scanning mirror 17.

A case 25 in which a meniscus lens 24, which has a smaller radius of curvature on the exit surface than the entrance surface and is convex toward the image forming surface, is housed in the front surface of the cover member 18 by resin molding is shown in FIG. As shown in, it is screwed so that it can be attached and detached from the outside. The meniscus lens 24
Is configured to form an image of the deflected light obtained by being reflected by the scanning mirror 17 on the photosensitive surface of a photosensitive drum (not shown). The meniscus lens 24 may be glass-polished or resin-molded.

As shown in FIG. 5, the scanning mirror 17 has three prisms 171, 172, whose both end surfaces are right triangles.
173 are combined to form a prism 171,
One of the two surfaces sandwiched between the two short sides of the end surface of 172 is defined as semi-transmissive first reflective surfaces 171a and 172a,
The other is made into the 2nd reflective surface 171b, 172b, and the 2nd reflective surface 171b, 172b is each laminated | stacked by two surfaces pinched | interposed between two short sides of the end surface in the prism 173. The center of one surface of the prism 173, which is sandwiched between the two long sides of the end surface, is positioned so as to be aligned with the center of the rotary shaft 12b of the scanner motor 12, and is fixed to the rotor 12a, for example, by adhesion.

As the prisms 171, 172, 173, for example, acrylic of the same shape is used, and a portion which becomes a reflective surface of acrylic is subjected to Cr (chrome) vapor deposition to form a semi-transmissive surface.

Next, the operation of the apparatus of this embodiment will be described.

The laser light from the semiconductor laser oscillator 19 is converted into a diverging light flux by the converging lens 20, and then shaped into a circular beam by the slit 21. This beam is reflected by the reflection mirror 23 and becomes a light beam parallel to the rotating shaft 12b of the scanner motor 12, and each prism 1 of the scanning mirror 17 is formed.
It is incident on the center of the boundary between 71 and 172.

As shown in FIG. 6, in the scanning mirror 17, half L1 of the incident laser beam is separated into reflected light and transmitted light by the first reflecting surface 171a of the prism 171, and the reflected light is opposed to the prism 172. Deflection light L10
Is emitted as. The transmitted light is the second light of the prism 171.
The light is further reflected by the reflecting surface 171b and emitted as a light beam L11 to the side opposite to the deflected light L10.

The other half L2 is the first half of the prism 172.
The reflected light is separated into reflected light and transmitted light by the reflecting surface 172a, and the transmitted light is further reflected by the second reflecting surface 172b of the prism 172 and emitted as the deflected light L21. Further, the reflected light is transmitted through the prism 171 which is opposed to the prism 171, and is emitted as a light beam L20 to the side opposite to the deflected light L21.

In this way, the two polarized lights L10 and L21 are combined and emitted to the outside through the meniscus lens 24.

As described above, since the laser light flux from the semiconductor laser oscillator 19 is incident on the center of the boundary of each prism 171 and 172 of the scanning mirror 17, each prism 171 and 172 is rotated even if the scanning mirror 17 is rotated by the motor 12. There is no vertical movement of the deflecting point on the reflecting surface of, and stable and accurate deflected scanning light can be emitted.

When the scanner motor 12 rotates 180 °, the light flux L20 and the light flux L11 are emitted as deflected light to the outside through the meniscus lens 24, so that the motor 12 can be scanned twice per rotation. Therefore, it is possible to easily realize high-speed scanning.

In the prisms 171 and 172, the first reflecting surfaces 171a and 172a are semi-transmissive reflecting surfaces, but the second reflecting surfaces 171b and 172b are normally totally reflected (refractive index 1.5 and critical angle 41.8). Therefore, it is not necessary to specify the reflectance or the transmittance, and therefore, a semi-transmissive reflective surface similar to the first reflective surface may be used to facilitate manufacture. Further, since the surfaces 171c and 172c sandwiched between the two long sides of the end surfaces of the prisms 171 and 172 are surfaces through which the laser light flux is emitted to the outside, it is desirable that the transmittance be as high as possible.

Regarding the power distribution of the deflected lights L10 and L21, the first reflection surfaces 171a and 171a of the prisms 171 and 172 are used.
If the reflectance of 72a is R, then L10 = L21 × R,
Power distribution becomes asymmetric. In order to solve this, the surfaces 171c and 172c which become the emission surfaces of the prisms 171 and 172
It may be possible to make a difference in the transmittance of the laser beam from above and below, but when applying it to a laser printer, for example, it is the power and the beam diameter that contribute to the exposure characteristics. If it is obtained and the beam diameter is set appropriately, the asymmetry of power will not be a problem in practical use.

In the above embodiment, the reflected light from the first reflecting surface of the prism and the reflected light from the second reflecting surface are combined into the deflected light, but only the reflected light from the first reflecting surface is deflected light. It may be one that creates Also in this case, it is necessary to obtain the required minimum power or more and to set the beam diameter appropriately.

In the above embodiment, the prisms 171, 1
Although the prism 173 is used to support the 72, the prism 173 does not participate in the bending of the light flux. Therefore, instead of the prism 173, a low-precision iron-based material is used to support the prisms 171 and 172. Good. Alternatively, the portion of the prism 173 may be a space and the portion may be filled with an adhesive.

Although the reflecting surface of the scanning mirror is formed by the two prisms 171, 172 in the above embodiment, this portion may be integrally formed by resin molding.

In the above embodiment, the scanning mirror has two prisms, each of which has a semi-transmissive surface and two reflective surfaces facing each other. However, the invention is not limited to this. For example, four pyramidal prisms. It is also possible to use a device in which two sets of opposing semi-transmissive surfaces and four reflecting surfaces are formed by using, so that scanning can be performed four times with one rotation of the scanner motor.

[0035]

As described above, according to the present invention, it is possible to perform scanning a plurality of times with one rotation, and moreover, it is possible to perform accurate deflection scanning without changing the deflection point due to the rotation of the reflector.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view showing a state in which a cover member is omitted in the embodiment.

FIG. 3 is a front view of FIG. 1 viewed from an arrow A.

FIG. 4 is a rear view of FIG. 1 viewed from an arrow B.

FIG. 5 is a perspective view showing a configuration of a scanning mirror in the embodiment.

FIG. 6 is a view for explaining the action of the scanning mirror in the embodiment.

FIG. 7 is a diagram showing an example of a conventional deflector.

[Explanation of symbols]

12 ... Scanner motor, 12a ... Rotor, 12b ... Rotating shaft, 17 ... Scanning mirror, 22 ... Light emitting unit.

Claims (2)

[Claims] 1. A motor for rotatively driving a rotor mounted on a rotary shaft, a means for causing a light beam parallel to the rotary shaft direction to be incident on the rotary shaft of the motor, and a means for positioning the motor on the rotary shaft of the motor. The scanning mirror is provided and is rotationally driven by the motor, wherein the scanning mirror has even number of semi-transmissive reflective surfaces having the same inclination angle facing each other at an angle of 90 °, and the boundaries of the respective semi-transmissive reflective surfaces. An optical scanning device, characterized in that the optical scanning device is installed so that substantially the center of the light beam is incident on the light beam. 2. A motor for rotatively driving a rotor mounted on a rotary shaft, means for causing a light beam parallel to the rotary shaft direction to be incident on the rotary shaft of the motor, and the motor being located on the rotary shaft of the motor. The scanning mirror is provided and is rotatably driven by the motor, the scanning mirror having even-numbered semi-transmissive first reflecting surfaces facing each other at an angle of 90 ° and having equal inclination angles, and each of the first reflecting surfaces. And a second reflecting surface for reflecting a light beam transmitted through the corresponding first reflecting surface at an angle of 90 ° in a direction opposite to the direction of reflection of the light beam by the first reflecting surface. An optical scanning device, which is installed so that a substantially center of a light flux is incident on a boundary of the optical scanning device.