JP2008286851A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical scanner capable of miniaturization and suppressing the generation of an erroneous signal of write-in position information. <P>SOLUTION: The optical scanner is provided with: a laser diode 1; a polygon mirror 5 which deflects a luminous flux radiated from the laser diode 1 in a main scanning direction Y; scanning lenses 11 and 12 which image the luminous flux deflected with the polygon mirror 5 on a face to be scanned (photoreceptor drum 40); a sensor 25 which receives the luminous flux from the polygon mirror 5 for detecting the write-in position of an image; and an optical path bending member 21 to guide the luminous flux from the polygon mirror 5 to the sensor 25. The luminous flux emitted from the optical path bending member 21 and directed to the sensor 25 crosses the front face of the scanning lens 11 arranged on the side of the polygon mirror 5 in the main scanning direction Y and the luminous flux emission position of the optical path bending member 21 and the luminous flux incident position on the sensor 25 are different from each other in a subscanning direction Z. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical scanning device, and more particularly to an optical scanning device that is mounted on an electrophotographic image forming apparatus and forms an electrostatic latent image on a photoreceptor.

  Conventionally, in this type of optical scanning device, a sensor (hereinafter also referred to as an SOS sensor) that receives a light beam deflected in the main scanning direction by a deflector in order to detect the writing position of an image written line by line. Is arranged. The configuration and arrangement of the SOS sensor are described in Patent Documents 1 to 4. However, the conventional SOS sensor has a problem that it causes an increase in the size of the optical scanning device and an erroneous signal of writing position information occurs. Hereinafter, this problem will be described.

  FIG. 10 shows a conventional optical scanning device. The light beam emitted from the laser diode 101 passes through the collimator lens 102, the aperture 103, and the cylindrical lens 104 and enters the reflection surface of the polygon mirror 105. The light beam is deflected in the main scanning direction Y as the polygon mirror 105 rotates, and is imaged on the surface to be scanned (photosensitive drum 120) by the scanning lenses 111 and 112 and scanned at a constant speed. A part of the deflected light beam passes through the scanning lens 112, is reflected by the optical path bending mirror 115, and scans the light receiving surface of the SOS sensor 117 through the condenser lens 116. An image writing position is determined based on a signal from the SOS sensor 117.

  In order to reduce the size of such an optical scanning device, it is conceivable to bring the SOS sensor 117 and the mirror 115 closer to the polygon mirror 105 and shorten the dimension of the housing in the optical axis direction X. In this case, the SOS sensor 117 and the mirror 115 are arranged near the front surface of the scanning lens 111 or the scanning lens 112, and the light beam traveling from the mirror 115 toward the SOS sensor 117 passes near the front surface of the scanning lens 111 or the scanning lens 112. .

  Further, in order to detect the writing position, the light beam is not necessarily emitted from the laser diode 101 only at the moment when the light beam is incident on the SOS sensor 117, but the light beam is emitted from before the incident, and the SOS sensor 117. The upper side is scanned from the polygon mirror 105 side to the surface to be scanned.

Accordingly, when the mirror 115 and the SOS sensor 117 are brought close to the scanning lenses 111 and 112, the light flux before entering the SOS sensor 117 is incident from the surface on the scanned surface side of the scanning lenses 111 and 112 and the surface on the polygon mirror 105 side. After being reflected by the inner surface, the light is emitted from the surface to be scanned and enters the SOS sensor 117 as ghost light, and an erroneous signal of the writing start position information is generated.
JP-A-5-93877 JP-A-7-228004 JP-A-8-110490 JP 2006-354681 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical scanning device that can reduce the size of the device and suppress the occurrence of erroneous signals of writing position information.

In order to achieve the above object, the present invention provides:
A light source, a deflector that deflects the light beam from the light source in the main scanning direction, at least one scanning lens that forms an image of the light beam deflected by the deflector on the surface to be scanned, and an image writing position are detected In order to do so, in an optical scanning device comprising: a sensor for receiving a light beam from the deflector; and an optical path bending member for guiding the light beam from the deflector to the sensor,
The light beam emitted from the optical path bending member and directed to the sensor crosses the front surface of the scanning lens disposed on the deflector side in the main scanning direction, and the light beam emission position of the optical path bending member and the sensor The light beam incident position at is different in the sub-scanning direction,
It is characterized by.

  In the optical scanning device according to the present invention, the ghost light emitted from the optical path bending member has an angle in the sub-scanning direction with respect to the scanning lens disposed on the deflector side of the optical path bending member or the SOS sensor. Incident. Ghost light is sub-scanned from the light beam that is directed directly from the optical path bending member to the SOS sensor due to two refractions of incidence / emission on the surface to be scanned side of the scanning lens and internal reflection on the surface on the deflector side. It will head to the SOS sensor at different angles in the direction. Therefore, the ghost light passes through a height different from that of the normal light flux in the sub-scanning direction and is not incident on the SOS sensor, so that an erroneous signal of the writing position information can be suppressed.

  In the optical scanning device according to the present invention, the optical path bending member may have a curved surface for condensing the light beam from the deflector at least in the main scanning direction, or at least sub-scan the light beam from the deflector. You may have the curved surface for condensing in a direction. Moreover, the reflection surface of the optical path bending member may be a single free-form surface, and the normal of the free-form surface at the light beam exit position may be inclined at least with respect to the main scanning direction. The optical path bending member may have at least two reflecting surfaces, or the positions of incident light and outgoing light of the optical path bending member may be different in the sub-scanning direction.

  Furthermore, at least two reflecting surfaces of the optical path bending member may be constituted by a prism, and this prism may have a light collecting action. Further, the reflection of the light beam by the prism may be based on total reflection.

  Embodiments of an optical scanning device according to the present invention will be described below with reference to the accompanying drawings.

(Schematic configuration of optical scanning device, see FIG. 1)
FIG. 1 shows a schematic configuration of an optical scanning device according to the present invention. The optical scanning device includes a light source unit, a polygon mirror 5, a first scanning lens 11, a second scanning lens 12, and a window (dustproof) glass 13. The light source unit includes a laser diode 1, a collimator lens 2, an aperture 3, and a cylindrical lens 4. Furthermore, an optical path bending member 21 and an SOS sensor 25 are provided.

  The light beam (diffused light) emitted from the laser diode 1 is condensed into substantially parallel light by the collimator lens 2, passes through the cylindrical lens 4 from the aperture 3, and condenses in the sub-scanning direction Z near the reflection surface of the polygon mirror 5.・ Image is formed. This light beam is deflected in the main scanning direction Y at a constant angular velocity based on the rotation of the polygon mirror 5, is imaged on the photosensitive drum 40 by the scanning lenses 11 and 12, and is scanned at a constant speed. In addition, a part of the light beam transmitted through the first scanning lens 11 is reflected by the optical path bending member 21 and condensed on the light receiving surface of the SOS sensor 25.

(Refer to the first embodiment, FIGS. 2 to 5)
FIG. 2 shows the SOS optical path in the first embodiment. In the first embodiment, as the optical path bending member, as shown in FIG. 5, a mirror 22 having a reflecting surface 22a is used. The optical path bending mirror 22 is disposed so as to be inclined at a predetermined angle in the sub-scanning direction Z. The light beam emitted from the mirror 22 crosses the front surface of the first scanning lens 11 in the main scanning direction Y, and the SOS sensor 25. Is incident on. Therefore, the light beam emission position of the optical path bending mirror 22 and the light beam incident position of the SOS sensor 25 are different in the sub-scanning direction Z.

  Here, construction data of the optical system from the polygon mirror 5 to the light receiving surface of the SOS sensor 25 in the first embodiment is shown in Table 1, and the optical path bending mirror 22 (fourth surface) and the light receiving surface (first surface) of the SOS sensor 25 are shown. Table 2 shows the normal vectors (eccentric data) of (5 planes). The surface shape of the first scanning lens 11 (third surface) and the surface shape of the optical path bending mirror 22 (fourth surface) are free-form surfaces, and their aspheric data are shown in Tables 3 and 4. The free-form surface is calculated by the free-form surface equation shown in Equation (1).

  For comparison, FIG. 7 shows an SOS optical path when the optical path bending mirror 22 is not inclined in the sub-scanning direction Z. Table 5 shows construction data of the optical system in this comparative example, and Table 6 shows normal vectors (eccentric data) of the optical path bending mirror 22 (fourth surface) and the light receiving surface (fifth surface) of the SOS sensor 25. . Only the normal line of the SOS sensor 25 and the Z coordinate of the light receiving surface of the SOS sensor 25 are different from the first embodiment, and the surface shape is the same as that of the first embodiment (see Tables 3 and 4).

  FIG. 2 showing the first embodiment and FIG. 7 showing the comparative example both show a deflection angle of 69 ° in which the light beam is collected at the center of the light receiving surface 25a of the SOS sensor 25. Further, FIG. 3 showing the first embodiment and FIG. 8 showing a comparative example show the SOS optical path when the deflection angle is 72.3 °. In the case of the deflection angle of 72.3 ° shown in FIGS. 3 and 8, the light beam from the optical path bending mirror 22 is incident from the second surface of the first scanning lens 11 and reflected by the inner surface of the first surface, The light is emitted from the two surfaces and reaches the SOS sensor 25.

  In the case of the comparative example shown in FIG. 8, since the optical path bending mirror 22 has no inclination in the sub-scanning direction Z, the light beam reflected by this mirror 22 is sub-reflected and reflected by the first scanning lens 11. Heading toward the light receiving surface 25a of the SOS sensor 25 without changing the angle in the scanning direction Z. Therefore, as shown in FIG. 9, the light condensing state on the light receiving surface 25a of the SOS sensor 25 has a large diameter different from the normal light flux, and the position in the sub-scanning direction Z is the same position as the normal light flux. That is, the ghost light G (deflection angle 72.3 °) is incident on the light receiving portion 25b of the SOS sensor 25 before the regular light beam (deflection angle 69 °), and erroneous writing position information is generated. .

  In contrast, in the first embodiment, the optical path bending mirror 22 has an inclination in the sub-scanning direction Z, and the light beam reflected by the mirror 22 is about 2.4 ° in the sub-scanning direction Z. It is designed to enter the SOS sensor 25 at an angle Z coordinate 5.5 (see Table 1). In this case, since the ghost light is incident on the first scanning lens 11 with an inclination in the sub-scanning direction Z, the refracted light of the first scanning lens 11 is reflected by two refractions and one internal reflection by the first scanning lens 11. The angle of the light beam emitted from the second surface in the sub-scanning direction Z is about −1.3 °, and the Z coordinate on the light receiving surface 25a of the SOS sensor 25 is 0.4.

  As shown in FIG. 4, the ghost light G has a large diameter and about 3 mm in the sub-scanning direction as in the comparative example. However, since the distance between the light receiving unit 25b (Z = 5.5) and the center of the ghost light G (Z = 0.4) is 5.1 mm, the ghost light G is not incident on the light receiving unit 25b. No write position information is generated. Incidentally, the dimension of the light receiving portion 25b in the sub-scanning direction Z is 2.5 mm.

(Refer to the second embodiment, FIG. 6)
FIG. 6 shows an optical path bending member used in the optical scanning device according to the second embodiment. This optical path bending member is constituted by a prism 23 and is arranged at the same position as the optical path bending mirror 22. Other configurations of the optical scanning device are the same as those of the first embodiment (see FIG. 1).

  The light beam is incident from an incident surface 23a formed of a free-form surface, is internally reflected by the reflecting surfaces 23b and 23c, and is changed in height in the sub-scanning direction Z, and is emitted from the exit surface 23d with an angle in the sub-scanning direction Z. To the SOS sensor 25. Further, the light beam is condensed on the light receiving surface 25a of the SOS sensor 25 by the free curved surface of the incident surface 23a.

  Table 7 shows construction data of the optical system from the polygon mirror 5 to the light receiving surface of the SOS sensor 25 in the second embodiment, and Table 8 shows normal vectors (eccentric data) of the light receiving surfaces of the prism 23 and the SOS sensor 25. Show. The surface shape of the first scanning lens 11 (third surface) and the surface shape of the incident surface 23a (fourth surface) of the prism 23 are free-form surfaces, and the aspherical data of the first scanning lens 11 (third surface) is Table 9 shows the aspheric data of the incident surface 23a (fourth surface) of the prism 23, which is the same as in Table 3.

  Also in the second embodiment, similarly to the first embodiment, the ghost light that re-enters the first scanning lens 11 and then travels toward the SOS sensor 25 has an angle different from the normal light flux in the sub-scanning direction Z. As shown in FIG. 4, it reaches the position deviated from the light receiving portion 25b of the SOS sensor 25, and erroneous writing position information is not generated.

  In addition, the error sensitivity of the individual reflecting surfaces of the prism 23 is increased to some extent. However, since the error sensitivity is low when the prism 23 is incorporated in a housing as a unit, the assembly process can be performed with high accuracy if the mold is made highly accurate and resin-molded. There is no need to do it. Furthermore, since the two reflections by the reflection surfaces 23b and 23c are total reflection, the metal 23 is not required to be deposited, and the prism 23 can be manufactured at a low cost.

(Other examples)
The optical scanning device according to the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the gist.

  In particular, the configuration of the light source unit and the configuration and shape of the scanning lens are arbitrary. Of course, the various data shown in each embodiment is an example. The present invention can be applied not only to the SOS sensor that detects the writing position but also to the EOS sensor that detects the writing end position of the scanning line.

1 is a schematic configuration diagram showing an optical scanning device according to the present invention. It is a perspective view which shows the SOS optical path in 1st Example. It is a perspective view which shows the ghost light in 1st Example. It is explanatory drawing which shows the condensing state of the ghost light on the light-receiving surface of the SOS sensor in 1st Example. It is a perspective view which shows the optical path bending member (mirror) used in 1st Example. It is a side view which shows the optical path bending member (prism) used in 2nd Example. It is a perspective view which shows the SOS optical path in a comparative example. It is a perspective view which shows the ghost light in a comparative example. It is explanatory drawing which shows the condensing state of the ghost light on the light-receiving surface of the SOS sensor in a comparative example. It is a schematic block diagram which shows the conventional optical scanning device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser diode 5 ... Polygon mirror 11, 12 ... Scan lens 21 ... Optical path bending member 22 ... Optical path bending mirror 23 ... Prism 40 ... Photosensitive drum (scanned surface)
Y ... Main scanning direction Z ... Sub scanning direction

Claims (9)

A light source, a deflector that deflects the light beam from the light source in the main scanning direction, at least one scanning lens that forms an image of the light beam deflected by the deflector on the surface to be scanned, and an image writing position are detected In order to do so, in an optical scanning device comprising: a sensor for receiving a light beam from the deflector; and an optical path bending member for guiding the light beam from the deflector to the sensor,
The light beam emitted from the optical path bending member and directed to the sensor crosses the front surface of the scanning lens disposed on the deflector side in the main scanning direction, and the light beam emission position of the optical path bending member and the sensor The light beam incident position at is different in the sub-scanning direction,
An optical scanning device characterized by the above.   The optical scanning device according to claim 1, wherein the optical path bending member has a curved surface for condensing a light beam from the deflector at least in a main scanning direction.   The optical scanning device according to claim 1, wherein the optical path bending member has a curved surface for condensing a light beam from the deflector at least in a sub-scanning direction.   The optical path bending member has a reflecting surface formed of one free-form surface, and a normal line of the free-form surface at a light beam exit position is inclined at least with respect to the main scanning direction. The optical scanning device according to claim 1.   5. The optical scanning device according to claim 1, wherein the front optical path bending member has at least two reflecting surfaces.   6. The optical scanning device according to claim 5, wherein positions of incident light and outgoing light of the optical path bending member are different in the sub-scanning direction.   7. The optical scanning device according to claim 5, wherein at least two reflecting surfaces of the optical path bending member are formed of prisms.   The optical scanning device according to claim 7, wherein the prism has a light collecting function.   9. The optical scanning device according to claim 7, wherein the light beam is reflected by the prism by total reflection.

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