JP2005208662A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a light beam, reflected on the surface of a light beam detector, from reaching a surface to be scanned. <P>SOLUTION: In an optical scanner which has a light source; a deflector which deflects a light beam emitted from the light source; a scanning optical system which forms the imaging of the scanning light beam deflected by the deflector on a prescribed surface to be scanned; a light beam detector which detects that the scanning light beam arrived at the prescribed position; and an separating mirror for leading the scanning light beam to the light beam detector and which scans the surface to be scanned with the scanning light beam, based on the detected signal of the light beam detector, the light beam reflected on the surface of the detector is shielded by a shielding plate, provided on the upstream side of the scanning of the separating mirror. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical scanning device used in a laser beam printer or the like, and more particularly to an optical system structure that guides a light beam to a detector that detects the position of the light beam.

  In an image recording apparatus such as a laser beam printer and an optical scanning apparatus used in various image reading and measuring apparatuses, a rotating polygon mirror has been often used as a deflector for deflecting and scanning a light beam.

  In these apparatuses, a light beam is repeatedly scanned on a surface to be scanned on a straight line or a curved line by an optical scanning device, and a scanning medium positioned on the surface to be scanned is relatively moved in a direction substantially orthogonal to the scanning direction. Two-dimensional scanning is performed. Note that the scanning direction of the former optical scanning device is defined as “main scanning direction”, and the relative movement direction of the latter scanning medium is defined as “sub-scanning direction”.

  In general, when the optical scanning device is applied to an image recording device or an image input device, a means for generating a synchronization signal as a base point of each scanning is required. For this reason, a method is widely used in which a detection optical system for guiding the light beam to a light beam detector located in the middle of the optical path from the deflector for deflecting the light beam to the surface to be scanned and before the effective scanning region is used. Various detection optical systems have been devised in order to prevent the lenses and reflection mirrors that constitute such a detection optical system from interfering with the light beam that scans the effective area on the surface to be scanned.

  In recent years, higher speed optical scanning devices have been required for the above-described devices in order to improve resolution and processing speed. In an optical scanning device using a rotating polygon mirror for deflecting a light beam, in order to increase the scanning speed (scanning frequency), (1) increase the rotation number of the rotating polygon mirror (2) increase the number of surfaces of the rotating polygon mirror Two methods are possible.

  In order to increase the rotational speed of the rotary polygon mirror, a bearing capable of high-speed rotation is required. However, the maximum number of ball bearings currently used is about 20,000 revolutions per minute. If an air bearing is used, it can be used at a rotational speed of 30000 revolutions per minute or more, but the apparatus that can be used is limited because the bearing is expensive. In particular, it cannot be used for inexpensive laser beam printers for general consumers.

  On the other hand, when the number of surfaces of the rotating polygon mirror is increased, the rotation angle per one reflecting surface is decreased. Also, if the size of each reflecting surface is to be secured above a certain level, the diameter of the rotating polygon mirror will increase.

  In order to solve this problem, in Patent Document 1, a light beam emitted from a light source is incident on a rotating polygon mirror in a state of a very small diameter in the main scanning direction, and the deflected light beam is transmitted via a transmission optical system. A method of making it incident on a rotating polygon mirror again is disclosed. After entering the rotary polygon mirror for the second time, the light beam is imaged as a spot on the surface to be scanned by the scanning optical system. That is, the light beam is incident twice on the rotating polygon mirror.

  In this latter method, the diameter of the light beam in the main scanning direction when the light beam first enters the rotating polygon mirror is made extremely small compared to the case where it enters the second time, and the second time the rotating polygon mirror is applied to the rotating polygon mirror. The transmission optical system is configured so that the incident light beam follows the center point in the main scanning direction of the rotating reflecting surface.

  However, since the deflection angle of the light beam incident on the rotary polygon mirror for the second time with respect to the optical axis is not so large, the scanning angle of the finally obtained light beam cannot be increased. Therefore, the focal length of the scanning optical system is longer and the optical path length from the second reflecting surface to the surface to be scanned must be longer than that of a normal optical scanning device in which a light beam is incident on the rotary polygon mirror only once. I didn't get it.

  On the other hand, even in a normal optical scanning device in which a light beam is incident on the rotary polygon mirror only once, the field angle and astigmatism increase as the deflection angle of the light beam deflected by the deflector increases, that is, as the lens becomes wider. It becomes difficult to simultaneously satisfy aberration and constant speed scanning (so-called fθ characteristics). On the other hand, if the deflection angle of the light beam is reduced, it is easy to keep the above optical characteristics good, but the distance from the deflector to the surface to be scanned tends to be longer because the focal length of the scanning optical system becomes longer. It is in.

JP-A-51-32340

  In the optical scanning apparatus described in the above-mentioned section of the prior art, a photodiode or a phototransistor is used as a photoelectric conversion element in the light beam detector. Usually, these elements are enclosed in a transparent package. use. In some cases, an amplifier circuit and a pulse generation circuit are integrated adjacent to the photoelectric conversion element. When a light beam is incident on such an element, most of the optical power is absorbed by the element, but some is reflected by the surface of the transparent package or the element surface. Further, when a light beam is incident on the circuit portion, scattering reflection occurs.

  Usually, in order to increase the efficiency of the light beam incident on the photoelectric conversion element, the incident light beam is arranged to be perpendicular to the surface of the element. Accordingly, the reflected light generated for the above reason goes back in the same path as the incident light beam.

  However, on the reflection mirror that separates the light beam for detection, the distance between the position where the light beam should be detected by the above-described element and the position of the light beam corresponding to the head portion (writing portion) of the effective scanning region is as much as possible. The scanning angle of the deflector and the scanning optical system can be reduced by making it smaller. For this reason, when the reflected light returns to the position of the reflection mirror, if it is slightly displaced toward the effective scanning region, the reflection mirror is detached and the surface is directed toward the surface to be scanned. For this reason, there are problems such as inadvertently irradiating the surface to be scanned to form an unnecessary image or noise in the input information.

  In particular, in an optical scanning apparatus having a tilt correction lens at a position relatively close to the image plane, the above-described reflection mirror is provided in front of the tilt correction lens, and a lens corresponding to the tilt correction lens is also provided in the beam detection optical system. However, the above-described reflected light is focused in the sub-scanning direction, which is a bigger problem.

  In view of the above problems, an object of the optical scanning device of the present invention is to prevent the light beam reflected by the light beam detector from reaching the surface to be scanned.

  In order to solve the above problems, in the optical scanning device of the present invention, a light source, a deflector for deflecting the light beam emitted from the light source, and the scanning light beam deflected by the deflector are coupled to a predetermined surface to be scanned. A scanning optical system for imaging, a light beam detector for detecting that the scanning light beam has reached a predetermined position, and a separation mirror for guiding the scanning light beam to the light beam detector. In an optical scanning device that scans a surface to be scanned with a scanning light beam based on a detection signal, a detection element surface constituting the light beam detector or a package surface enclosing the element with respect to the light beam incident on the light beam detector Is tilted in a direction different from the vertical direction in the main scanning plane, and the light beam reflected by the detection element surface or the package surface is shielded by a shielding plate provided on the scanning upstream side of the separation mirror. And wherein the Rukoto.

  Further, the deflector is a rotary polygon mirror having at least a first reflection surface and a second reflection surface, and deflects the light beam emitted from the light source with the first reflection surface. A transmission optical system that makes the light beam deflected by the reflecting surface incident on the second reflecting surface of the rotary polygon mirror, and scanning the scanning light beam deflected by the second reflecting surface by the scanning optical system. Features.

  As described above, in the optical scanning device of the present invention, in the main scanning direction, the surface of the light beam detector is inclined with respect to the incident light beam, and the light beam detector element is enclosed. If the reflected light reflected from the surface of the element or the surface of the element itself is reflected by the previous folding mirror and directed to the shielding plate provided upstream in the scanning direction of the separation mirror, The light beam reflected by the surface does not pass through the correction lens and travel toward the scanned surface, and it is possible to prevent unnecessary irradiation of the scanned surface.

  FIGS. 1 and 2 are perspective views showing an overview of the first embodiment of the optical scanning device according to the present invention. FIG. 2 shows a state in which the correction lens 62 and the third folding mirror 93 are removed from FIG. It is a perspective view. FIGS. 3 and 4 are plan views of the first embodiment of the optical scanning device according to the present invention in the main scanning section. 3 and 4, the light beam after the first reflecting surface 31 of the rotary polygon mirror 30 is a light beam at four positions: a beam detection position, a scanning start position, an optical axis position of the scanning optical system, and a scanning end position. Indicates the position. FIG. 3 shows a scanning optical system and a light beam detecting optical system and a light beam passing therethrough, and FIG. 4 shows a transmission optical system, a beam shaping optical system, and a light beam passing therethrough. Further, FIG. 5 shows a sectional view in the sub-scanning plane including the beam shaping optical system of the first embodiment of the optical scanning device according to the present invention, and FIG. 6 shows the first of the optical scanning device according to the present invention. FIG. 3 is a cross-sectional view in the sub-scanning plane including the scanning optical system of the embodiment.

  A semiconductor laser 11 is used as a light source, and a laser beam emitted as divergent light is shaped by a collimator lens 21 into a focused light beam having a gentle focusing angle. The exit surface of the collimator lens 21 is formed in an aspherical shape that is rotationally symmetric with respect to the optical axis in order to reduce spherical aberration.

  The light beam emitted from the collimator lens 21 is incident on a shaping lens 22 that is a cylindrical surface having a flat incident surface and a concave emission side. The shaping lens 22 has a negative refractive power only in the main scanning direction, and the incident focused light beam is converted into a parallel light beam having a relatively small diameter in the main scanning direction. On the other hand, in the sub-scanning direction, the focused light beam converted by the collimator lens 21 remains. The collimator lens 21 and the shaping lens 22 described above constitute a beam shaping optical system.

  That is, as shown in FIG. 4, the light beam incident on the first reflecting surface 31 of the rotary polygon mirror 30 is a parallel light beam having a smaller diameter in the main scanning direction than that of an ordinary optical scanning device, and is sub-scanned. In the direction, the focused light beam forms an image on the first reflecting surface 31. The rotary polygon mirror 30 will be described later.

  As described above, in the first embodiment of the present invention, the collimator lens 21 converts the light beam emitted from the semiconductor laser 11 into a loosely focused light beam at a position where the diameter of the light beam is expanded to some extent. A shaping lens 22, which is a concave cylindrical lens, is disposed at a distance, and is converted into a parallel light beam only in the main scanning direction. For this reason, the focal length of the collimator lens 21 can be made relatively large, thereby the radius of curvature of the lens surface of the collimator lens 21 can also be made large, and the processing of the lens surface or a mold for molding the lens surface becomes easy. Further, since the size of the lens surface is increased, the accuracy required for the lens surface due to aberrations is eased and the manufacture is facilitated, and at the same time, the imaging performance on the surface to be scanned can be expected to be improved.

  Further, in the first embodiment of the present invention, as shown in FIG. 4, the optical path from the semiconductor laser 11 as the light source to the first reflecting surface 31 of the rotary polygon mirror 30 can be made long. The distance from the first reflecting surface 31 to the light source unit becomes longer than the distance from the first reflecting surface 31 to the first reflecting mirror 51 of the transmission optical system described later when viewed in the scanning plane. Therefore, as shown in FIG. 5, there is no spatial restriction in the vertical direction of the light source unit, and in particular, the size of the drive circuit board of the semiconductor laser 11 can be arbitrarily set. Therefore, it is possible to integrate an electronic circuit for performing advanced control of the semiconductor laser 11, particularly gradation control, in the immediate vicinity of the semiconductor laser 11.

  The light beam exiting the shaping lens 22 is incident on the first reflecting surface 31 of the rotary polygon mirror 30. The optical axis of the beam shaping optical system through which the light beam incident on the first reflecting surface 31 passes and the optical axis of the transmission optical system through which the reflected light beam passes are within the main scanning plane as shown in FIG. overlapping. On the other hand, as shown in FIG. 5, it has an angle γ1 with respect to the perpendicular of the first reflecting surface 31 in the sub-scanning plane, that is, it is incident at an incident angle γ1 in the sub-scanning plane. Therefore, the light beam reflected and deflected by the first reflecting surface 31 and the incident light beam form an angle 2 · γ1 in the sub-scanning surface and do not interfere with each other. In this embodiment, γ1 is set to 6 °.

  The light beam reflected and deflected by the first reflecting surface 31 enters the transmission lens first group 41 constituting the transmission optical system. The transmission lens first group 41 includes, in order from the incident side, a first transmission lens composed of a plane and a convex cylindrical surface, a second transmission lens composed of a convex cylindrical surface and a plane, and a third transmission lens composed of a concave cylindrical surface and a plane. These lenses have a refractive power only in the main scanning direction.

  The light beam exiting the transfer lens first group 41 becomes a focused light beam in the main scanning direction, and once forms an image at the rear focal point of the transfer lens first group 41. The once-formed light beam becomes a divergent light beam, is reflected by the reflecting mirror 51, and travels toward the transfer lens second group 42. The second transmission lens group 42 is composed of a fourth transmission lens having a convex cylindrical surface on the incident side and a flat surface on the emission side. The transmission lens second group 42 has refractive power only in the sub-scanning direction.

  The light beam exiting the transfer lens second group 42 enters the transfer lens third group 43. The third transmission lens group 43 is composed of one fifth transmission lens having a cylindrical surface with a flat incident surface and a convex exit surface. The third transmission lens group 43 has refractive power only in the main scanning direction.

  The light beam that has exited the third transmission lens group 43 becomes a substantially parallel light beam in the main scanning direction. The direction of the optical axis is changed by the reflecting mirror 52 and the parallel light beam enters the second reflecting surface 32 of the rotating polygon mirror 30. As the light beam incident on the second reflecting surface 32 is deflected by the first reflecting surface 31, the center of the light beam moves so as to follow the center of the second reflecting surface 32. These transfer lens first group 41 to third group 43 constitute a transfer optical system.

  The diameter of the parallel light beam incident on the second reflection surface 32 in the main scanning direction is several times larger than the diameter of the parallel light beam incident on the first reflection surface 31. Since the light beam moves following the rotational movement, the size of the reflecting surface does not protrude.

  Further, the optical axis of the transmission optical system through which the light beam incident on the second reflecting surface 32 passes and the optical axis of the scanning optical system through which the deflected light beam passes are as shown in FIG. It overlaps inside. On the other hand, as shown in FIG. 6, in the plane including the rotation axis of the rotary polygon mirror 30, that is, in the sub-scanning plane, it is arranged in an oblique direction different from perpendicular to the second reflecting surface 32. In this embodiment, the angle of the light beam incident on the second reflecting surface 32 in the sub-scanning plane with respect to the normal of the reflecting surface, that is, the incident angle γ2 is 6 °.

  As the reflecting mirror 51 and the reflecting mirror 52 placed in the transmission optical system, a mirror having a reflective film deposited on the surface of float glass is used. The float glass produced continuously has a different flatness in the direction in which the manufacturing process proceeds and in the direction perpendicular thereto. In the first embodiment of the present invention, an inexpensive reflecting mirror can be used by matching the direction of good flatness with the main scanning direction. It should be noted that a predetermined thickness is required to maintain the flatness of the glass, which is the same for both polished glass and float glass. In this embodiment, a glass having a thickness of 5 mm is sufficient for the reflecting mirrors 51 and 52. Flatness is obtained.

  Also, when a reflecting mirror is interposed in the beam shaping optical system as well as the transmission optical system, it is possible to use an inexpensive float glass by matching the direction of good flatness with the main scanning direction in exactly the same manner as described above. Become. Furthermore, the reflecting mirror interposed in such a beam shaping optical system is not only an optical system in which a light beam is incident twice on the reflecting surface of the rotating polygon mirror as in the first embodiment of the present invention, but also in general. This scanning optical system can be widely applied to an optical system for guiding a light beam from a light source to a rotary polygon mirror.

  When the transmission optical system according to the first embodiment of the present invention is viewed in the sub-scan section, only the transmission lens second group 42 has optical refractive power, and the first reflecting surface 31 and the second optical system The reflecting surfaces 32 are arranged so as to have an optical conjugate relationship. For this reason, even if each of the first reflecting surfaces 31 of the rotating polygon mirror 30 is tilted in the sub-scanning direction and has an error, the reflected light beam is incident on the second reflecting surface 32 at the same position in the sub-scanning direction. . That is, it has a tilt correction function.

  Next, the light beam deflected by the second reflecting surface 32 enters the imaging lens 61 and the correction lens 62, is shaped into a focused light beam, and then forms an image on the scanned surface 71. The imaging lens 61 and the correction lens 62 constitute a scanning optical system, and a light beam scanned at a constant angular speed is scanned at a constant linear speed as the rotary polygon mirror 30 that rotates at a constant speed rotates. The surface 71 is scanned.

  As shown in FIG. 6, the light beam exiting the imaging lens 61 is folded back above the rotary polygon mirror 30 by the first folding mirror 91. The folded light beam is further folded by the second folding mirror 92 and enters the correction lens 62. The light beam exiting from the correction lens 62 is finally folded back by the third folding mirror 93 and travels toward the surface to be scanned 70. These three folding mirrors are attached to an optical case 82 serving as a container for the optical scanning device.

  In this way, when viewed in the sub-scanning plane including the optical axis of the scanning optical system, (A) a rotating polygonal surface from the second reflecting mirror 52 of the transmission optical system on the base member 81 or the optical case 82 described later. A part reaching the second reflecting surface 32 of the mirror 30, (B) a part reaching the first folding mirror 91 including the imaging lens 61 from the second reflecting surface 32 of the rotary polygon mirror 30 of the scanning optical system; C) Four stages of a part from the first folding mirror 91 to the second folding mirror 92, and (D) a part from the second folding mirror 93 to the third folding mirror 93 via the correction lens 62. The optical path is folded.

  In the first embodiment of the present invention, by adopting such a structure, the length in the optical axis direction of the scanning optical system of the optical scanning device can be shortened regardless of the optical path length of the entire scanning optical system.

  In the scanning optical system, since the light beam is rotationally deflected, as the distance from the second reflecting surface 32 of the rotary polygon mirror 30 increases, the swing width of the scanned light beam increases, and the required width of the folding mirror is increased. Will also increase. In contrast, in the case of the structure as described above, the width of the folding mirror increases as the distance from the bottom surface of the optical case 82 increases. Therefore, when the holding portions are provided on both sides of the folding mirror, the bottom (bottom surface of the optical case 82) Interference with the lens located on the side) and the scanned light beam.

  In addition, since all the folding mirrors are arranged on the surface side of the optical case, that is, the side on which the lens group constituting the rotating polygon mirror and the scanning optical system is placed, it is easy to assemble, adjust, and inspect. The manufacturing cost is reduced and the reliability of the device is increased.

  In particular, as in the first embodiment of the present invention, when the transmission optical system is located on the side close to the bottom surface of the optical case 82, the transmission lens and the reflecting mirror constituting the transmission optical system are avoided and folded back. It becomes easy to provide a mirror support.

  A spot obtained by forming an image of a light beam on the surface to be scanned 71 moves linearly in a direction corresponding to the rotation of the rotary polygon mirror 30 to form a scanning line. In the first embodiment of the present invention, as already described, the light beam is incident in the direction different from the right angle with respect to the rotation axis of the rotary polygon mirror 30 in the sub-scanning plane, and the obtained deflected light beam. Since the deflected light beam is deflected at an angle different from the direction perpendicular to the rotation axis of the rotary polygon mirror 30, the surface formed by sweeping the deflected light beam is not a flat surface but a conical surface. Accordingly, the trajectory of the light beam incident on the imaging lens 61 and the correction lens 62 is also curved, but the scanning optical system is configured so that the scanning line obtained on the scanned surface 71 is a straight line.

  A scanning object is placed on the scanned surface 71. Since the optical scanning device of the present invention scans the light beam only in one direction in the main scanning direction, it is necessary to move the scanning object in the sub-scanning direction orthogonal to the main scanning direction in order to realize two-dimensional scanning. . The movement in the sub-scanning direction may move the flat plate-like medium linearly, or may rotate the cylindrical medium having a rotation axis parallel to the scanning line direction. For example, when the optical scanning device of the present invention is used in a laser beam printer, a photosensitive member is placed on the secret scanning surface 71 and an electrostatic latent image is formed by scanning the light beam.

  Here, the characteristics of the optical path arrangement of the transmission optical system according to the first embodiment of the present invention will be described. As described so far, in the first embodiment of the present invention, the beam shaping optical system at the position of the rotary polygon mirror 30 at the time of scanning near the center of the scanning range of the optical scanning device within the main scanning plane. The positional relationship between the optical axis of the transmission optical system incident on the first reflecting surface 31 or the second reflecting surface 32 of the rotating polygon mirror 30 and the second reflecting surface 32 of the rotating polygon mirror 30 is as follows. The optical axes of the optical systems are arranged so as to be substantially perpendicular to the reflecting surfaces.

  In other words, the optical axis of each optical system that guides the light beam to the two reflecting surfaces of the rotary polygon mirror is not at a spatial “twist position” with respect to the rotation axis of the rotary polygon mirror. It is in a state of crossing. Such a positional relationship between the optical axis of the optical system and the reflecting surface is hereinafter defined as a “front incidence” state.

  In the first embodiment of the present invention, the size of the second reflecting surface 32 of the rotary polygon mirror 30 is most effective with respect to the cross-sectional diameter of the light beam by adopting the “front incidence” arrangement as described above. It is used for. The light beam incident from the beam shaping optical system moves relative to the first reflecting surface 31 of the rotary polygon mirror 30, but the reflection point moves in a direction substantially perpendicular to the incident light beam. Therefore, the size of the reflecting surface with respect to movement can be minimized.

  Thus, since the size of each reflecting surface can be reduced, the size of the rotary polygon mirror 30 can be minimized. Accordingly, the inertial moment of inertia, weight, and centrifugal force acting on the reflecting surface of the rotating polygon mirror can be reduced, and the rotating polygon mirror can be rotated to a higher rotational speed.

  In addition, as shown in FIG. 6, the lenses and reflecting mirrors constituting the transmission optical system and the lenses constituting the scanning optical system can be arranged separately in the sub-scanning plane, so that these lenses and reflecting mirrors are main-scanned. Since they do not interfere with each other in the plane, there is no restriction on the size of the lens, and good optical characteristics can be obtained.

  Next, the positional relationship between the two reflecting mirrors of the transmission optical system and each lens will be considered. As described above, in the first embodiment of the present invention, as shown in FIGS. 5 and 6, the optical axis of the portion after the second reflecting mirror 52 in the transmission optical system and the optical axis of the scanning optical system. Are arranged with an angle in the sub-scanning plane, there is no restriction on the size of the lens in the main scanning plane.

  Further, in the first embodiment of the present invention, the transmission lens first group 41 is located between the first reflecting surface 31 and the first reflecting mirror 51 of the rotary polygon mirror, and the second reflecting mirror 52 is located. The transmission lens second group 42 and the transmission lens third group 43 are located between the first reflection surface 32 and the second reflection surface 32. That is, since there is no lens on the optical axis of the transmission optical system after the second reflecting mirror 52, the transmission optical system lens and the scanning optical system lens do not overlap even when viewed on the main scanning plane. For this reason, there are no restrictions on the size and mounting method of the scanning optical system lens, particularly the imaging lens 61, and it is possible to use an imaging lens having an optically optimal position and size.

  Next, the positional relationship between the transmission optical system and the beam shaping optical system or scanning optical system according to the first embodiment of the present invention will be described.

  Further, as can be seen from FIG. 5 or FIG. 6, in the portion where the transmission optical system and the beam shaping optical system or the scanning optical system overlap in the main scanning plane, the vertical relationship of the optical axis with respect to the base member 81 that supports each lens and mirror. , The beam shaping optical system or the scanning optical system overlaps on the transmission optical system or on the side far from the bottom surface of the base member 81.

  In the first embodiment of the present invention, by adopting such a structure, the base member 81 is integrally formed with the base member 81 and supports the lens and the reflecting mirror constituting the transmission optical system. The protrusion height can be kept low, and these lenses and reflecting mirrors can be attached to the base member 81 with high accuracy.

  On the other hand, the mounting accuracy of the imaging lens 61 or the correction lens 62 constituting the scanning optical system may not be so high as compared with the transmission optical system. Not. On the other hand, the position accuracy of the lens and light source of the beam shaping optical system is very strict, but because the required accuracy is too strict, it must be adjusted. For this reason, the position accuracy of the member itself that supports the lens of the beam shaping optical system does not have to be so high, but rather a structure that is easy to adjust is desired. Also in this viewpoint, it is preferable that the beam shaping optical system is positioned on the transmission optical system because the adjustment work is facilitated.

  Further, in the first embodiment of the present invention, as shown in FIG. 8, the base member 81 manufactured in a high-precision machining direction is formed by integrating each lens of the transmission optical system, two reflecting mirrors, and a rotating polygon mirror. The other parts are attached to an optical case 82 manufactured by a general manufacturing method.

  For example, for the production of the base member 81, a method in which a metal cast by die-casting is machined only on a portion requiring accuracy, such as a lens or reflector mounting surface. Even when a plastic injection molding method is used, the desired accuracy can be obtained by using a special molding method or the like that has been developed recently and has small shrinkage after molding.

  On the other hand, the optical case 82 can be manufactured by a general processing method, and can be manufactured at low cost by, for example, injection-molding a polycarbonate resin containing glass fiber. In addition, depending on the shape, it can be manufactured by pressing a sheet metal.

  As described above, in the first embodiment of the present invention, the base member 81 requiring accuracy is limited to the minimum necessary size, and the other optical case 82 is manufactured by a relatively inexpensive manufacturing method. The manufacturing cost of the entire apparatus can be reduced.

  In this embodiment, the imaging lens 61 and the shaping lens 22 positioned above the transmission optical system in plan view have a simpler structure when attached to the base member 81 than to be attached to the optical case 82. As a result, the size of the base member 81 does not increase, so that the base member 81 is attached.

  Next, the follow-up action of the transmission optical system of the first embodiment of the optical scanning device of the present invention on the reflecting surface of the rotary polygon mirror 30 will be described in detail. FIG. 7 is a diagram showing the main scanning section of the transmission optical system of the optical scanning apparatus according to the present invention described with reference to FIG. 4 without extending the reflecting mirror 51 and the reflecting mirror 52. However, the transmission lens second group 42 is omitted because it has no refractive power in the main scanning direction.

  When the transmission optical system is viewed in the main scanning direction, the transmission lens first group 41 is placed such that the front focal point of the transmission lens third group 43 coincides with the rear focal position P of the transmission lens first group 41. Constitutes an afocal optical system. Accordingly, the light beam that has passed through the third transmission lens group 43 becomes a parallel light beam again, the direction of the optical axis is changed by the reflecting mirror 52, and is incident on the second reflecting surface 32 of the rotating polygon mirror 30.

  Now, the diameter wi of the parallel light beam incident on the first reflecting surface 31 at the position of the reflecting surface is set. Since the transmission optical system constitutes an afocal optical system, it is converted into a parallel light beam having a diameter wo at the position of the second reflecting surface 32. Here, assuming that the focal length of the transmission lens first group 41 is f1, and the focal length of the transmission lens third group 43 is f2, the value of the ratio of the diameter of the light beam obtained by dividing wo by wi is obtained by dividing f2 by f1. Equal to the value.

  Here, when the rotary polygon mirror 30 is rotated by θ1, the light beam is deflected by 2 · θ1 on the first reflecting surface 31. The deflected light beam passes through the transmission lens first group 41 and the third group 43 and is deflected at an angle θ2. This light beam intersects the optical axis at point Q. The distance between the deflected light beam and the optical axis is δ at the position where the light enters the second reflecting surface 32 after intersecting, and δ is equal to the amount of movement of the reflecting surface when the rotary polygon mirror 3 rotates θ1. .

  At this time, the deflected light beam is deflected to the side where the incident angle increases by an angle θ2 with respect to the second reflecting surface 32, so that the scanning angle θs of the light beam reflected by the second reflecting surface is θs. = 2 · θ1 + θ2. That is, the deflection angle of the light beam can be increased by θ2 as compared with a method in which the light beam is incident on the rotary polygon mirror only once or a method in which the light beam follows the second reflecting surface 32 while moving in parallel. it can.

  By the way, when the central ray of the light beam deflected by the first reflecting surface 31 of the rotating polygon mirror intersects the optical axis of the transmission optical system as described above, the number of times is only Q point. If the number of reflecting mirrors for turning back the optical path in the middle of the transmission optical system is an even number, the rotational movement direction of the second reflecting surface 32 coincides with the direction in which the light beam moves.

  More generally, it can be seen that when the number of times the deflected light beam intersects the optical axis is an odd number, the number of folding reflectors should be an even number. The number of reflecting mirrors in the transmission optical system should be as small as possible because the flatness affects the imaging performance on the surface to be scanned and the power efficiency of the optical system is reduced by the reflectivity. However, if there is not at least one reflecting mirror, the light beam cannot be returned to the same rotating polygonal mirror, so the minimum value is 1.

  In addition, in order to shorten the distance from the first reflecting surface to the second reflecting surface of the rotary polygon mirror, it is better that the number of times the deflected light beam intersects the optical axis is smaller, and in reality, it does not intersect at all. It is desirable not to set it so that it intersects only once.

  Considering these conditions, the following four combinations are realistic options. (1) The number of times the deflected light beam intersects the optical axis is zero, and the number of reflecting mirrors is one. (2) The number of times the deflected light beam intersects the optical axis is zero, and the number of folding reflectors is three. (3) The number of times the deflected light beam intersects the optical axis is one, and the number of folding reflectors is two. (4) The number of times the deflected light beam intersects the optical axis is one, and the number of folding reflectors is four.

  However, in the case of (1), the number of reflecting mirrors is 1, and it cannot be adopted because the “front incidence” state cannot be realized simultaneously with respect to two different reflecting surfaces of the rotating polygon mirror as in the present invention. .

  In the case of (2), since the number of reflecting mirrors is large, there is an increased risk that the imaging performance deteriorates due to the flatness of the reflecting mirrors. If the reflectance per one reflecting mirror is 85%, the optical power efficiency when passing through the reflecting mirror 3 surface is 61%. Furthermore, since the mounting angle accuracy of each reflecting surface affects the direction of the optical axis, it is not preferable for ensuring the positional accuracy through which the light beam passes. Similarly, in the case of (4), the number of another reflecting mirror increases, so the problem of (2) becomes more severe.

  Therefore, in the first embodiment of the present invention, as shown in FIG. 4, the number of reflection mirrors for turning back the optical path of the transmission optical system corresponding to the above (3) is set to 2, and the inside of the transmission optical system is deflected. The number of reflecting mirrors is minimized by making the incidence of the light beam on the rotating polygonal mirror 30 into front incidence by making the intersection of the moving light beam and the optical axis of the transmission optical system one. As a result, the attenuation of the optical power can be reduced and the optical path length of the transmission optical system can be shortened.

  Next, the number of reflecting surfaces of the rotary polygon mirror 30 will be described. In the first embodiment of the present invention, the number of surfaces of the rotary polygon mirror 30 is 12 which is a multiple of four. By making the number of surfaces of the rotating polygon mirror 30 a multiple of 4, the angle formed by the two reflecting surfaces simultaneously used by the rotating polygon mirror 30 can be set to 90 degrees. Of the tilting error and position error of the reflecting surface with respect to the rotation axis of the rotary polygon mirror 30, the phase of the two reflecting surfaces is shifted by 90 degrees for a component that changes gently (generally in a sine wave shape) in one rotation. Therefore, there is no case where both the first reflecting surface 31 and the second reflecting surface 32 have the worst values at the same time, so that the influence of the tilting error and the position error of the reflecting surface can be reduced. In addition, this effect is widely applied not only to an optical system having a configuration of front incidence as in the embodiment of the present invention, but also to an optical scanning device in which a light beam is incident twice on the same rotary polygon mirror.

  Further, as shown in FIG. 4, an angle η formed by the light beam incident on the first reflecting surface 31 and the light beam incident on the second reflecting surface 32 via the transmission optical system in the main scanning plane is set to 90. It became possible to make it. By arranging in this way, the distance on the optical axis from the first reflecting surface 31 to the second reflecting surface 32 can be appropriately ensured, and an optimally configured transmission optical system can be obtained.

  Furthermore, considering the mechanical design of the optical scanning device, there is an advantage that the layout of each element is easier when the optical axis of the beam shaping optical system and the optical axis of the scanning optical system are orthogonal. is there.

  On the other hand, when considering the processing method of the rotary polygon mirror, the index angle in the processing machine of the reflecting surface is often limited to an integer. That is, the angle of the adjacent reflecting surface is a divisor of 360. Therefore, in order to change the shape of the rotating polygon mirror to a regular polygon (regular polyhedron), a polygon mirror having the number of surfaces such as 10, 12, 15, and 18 surfaces can be processed. The 14th, 16th, and 17th surfaces may not be processed. Considering this condition and the condition that is a multiple of 4 described above, the number N of surfaces of the rotary polygon mirror 30 is 12 as shown in the first embodiment of the present invention. It is also suitable for processing a polygon mirror.

  Of course, if the angles formed by the reflecting surfaces of the rotating polygon mirror are not uniform, there will be no restriction as described above, but the size of each reflecting surface will be the same, and the optical system must be designed to match the small reflecting surface. Therefore, the size of the polygon mirror is wasted.

  Next, the light beam detection method according to the first embodiment of the present invention will be described. In general, when the optical scanning device is applied to an image recording device or an image input device, a means for generating a synchronization signal as a base point of each scanning is required. In the first embodiment of the optical scanning device of the present invention, the light beam is guided to the light beam detector 63 at a position before scanning the effective scanning region on the surface to be scanned, and the arrival of the light beam is converted into an electric signal. A synchronization signal is obtained by conversion. The light beam detector 63 does not necessarily have to be on the surface to be scanned 71. However, as the optical scanning device, the required scanning range is from the position of the light beam detector 63 to the rear end of the effective scanning area.

  More specifically, the light beam deflected by the rotary polygon mirror 30 is converted into a focused light beam in the main scanning direction by the imaging lens 61 and then folded by the first folding mirror 91 and the second folding mirror 92. As shown in FIG. 9, after being separated from the optical path toward the original scanned surface 71 by the separation mirror 64 provided immediately before the correction lens, the light beam detection lens passes through the second folding mirror 92 again. The light beam is converted into a light beam focused in the sub-scanning direction at 65 and then enters the light beam detector 63. In FIG. 9, the light beam incident on the light beam detector 63 is indicated by a symbol Ls.

  Thus, in the present invention, when the second reflecting surface 32 of the rotary polygon mirror 30 is used as a reference, the light beam detector 63 is at the same distance as the surface to be scanned 71 on the optical axis of the scanning optical system. Further, when viewed in the sub-scanning plane, the position of the light beam detector 63 is optically conjugated with respect to the second reflecting surface 32 of the rotary polygon mirror 30 in the same manner as the scanned surface 71. A beam detection lens 65 is provided.

  During the light beam deflection period, the light beam does not reach the scanned surface 71 while the light beam crosses the separation mirror 64. In order for the light beam detector 63 to detect the arrival of the light beam, it is necessary to turn on the light source immediately before the light beam reaches the light beam detector 63. A shielding plate 66 is provided at a portion located upstream of the scanning of the attachment portion of the separation mirror 64 so that the light beam during this lighting period does not enter the correction lens 62.

  In the present invention, as shown in FIG. 9, the surface of the light beam detector 63 is inclined with respect to the incident light beam in the main scanning plane, and the elements of the light beam detector 63 are The reflected light Lg reflected from the surface of the packaged package or the surface of the element itself is reflected by the second folding mirror 92 and travels toward the shielding plate 66, and thus passes through the correction lens 62 and is scanned. The surface 71 is prevented from reaching.

  Next, a structure for preventing the generation of a ghost image in the optical scanning device according to the first embodiment of the present invention will be described. In the first embodiment of the present invention, a shielding plate 34 is provided between the reflecting surface 33 and the imaging lens 61 as shown in FIG. The light beam reflected by the surface is prevented from entering the imaging lens 61. Needless to say, the shielding plate 34 is placed at a position that does not block the original scanning light beam deflected by the second reflecting surface 32 of the rotary polygon mirror 30.

  Note that, depending on the configuration of the optical system, the light beam that generates the ghost image may be a reflective surface adjacent to the first reflective surface 31 instead of the reflective surface 33 adjacent thereto. Even in such a case, the same effect can be obtained by placing the shielding plate 34 between the reflecting surface in question and the imaging lens 31.

  Next, a method for adjusting the optical system of the first embodiment described above will be described with reference to FIGS. The shaped light beam emitted from the beam shaping optical system is incident on the first reflecting surface 31 of the rotary polygon mirror 30, and a knife edge (M) 83 having an edge parallel to the sub-scanning direction on the extension line of the optical axis. A knife edge (S) 84 having an edge parallel to the main scanning direction is provided integrally with the optical case 82. The tips of these knife edges coincide with the optical axis L1 of the beam shaping optical system. In this embodiment, a knife edge (S) 84 is provided by cutting out the lower part of the side wall of the optical case 82.

  Around the two knife edges, as shown in FIG. 4, on the optical axis of the beam shaping optical system, a notch A, a knife edge (M) 83 and a knife are placed in front of the knife hedge (M) 83. A notch B is provided between the edges (S) 84 so that a sensor for detecting the optical power before and after passing through the knife edge can enter.

  The actual adjustment work is performed by irradiating the two knife edges with the light beam that has passed through the beam shaping optical system with the rotary polygon mirror 30 removed. The light beam that has passed through the beam shaping optical system is a parallel light beam in the main scanning direction. On the other hand, in the sub-scanning direction, the focused light beam forms an image on the first reflecting surface 31 of the rotary polygon mirror 30. Therefore, at the position of the knife edge, the light beam spreads to some extent in the sub-scanning direction.

  First, a sensor for detecting optical power is inserted into the notch A, and the power of the light beam is measured. Next, a sensor is inserted into the notch B, and the optical power of the light beam passing through the knife edge (M) 83 is measured. At this time, the tip of the knife edge (M) 83 coincides with the optical axis of the beam shaping optical system, so that the optical power at the notch B is exactly half of the optical power measured at the notch A. If the semiconductor laser 11 or the collimator lens 21 is adjusted in the main scanning direction, the beam shaping optical system is correctly adjusted in the main scanning direction.

  Similarly, the optical power at the notch B is compared with the optical power behind the knife edge (S) 84, that is, outside the optical case 81, and the semiconductor laser 11 or the collimator lens 21 is adjusted so that the optical power is exactly half. If the adjustment is made in the sub-scanning direction, the adjustment of the beam shaping optical system in the sub-scanning direction is completed. As described above, since the light beam spreads in the sub-scanning direction at the knife edge position, the detection accuracy is lowered, but the accuracy is practically sufficient and there is no problem.

  By using such an adjustment method, it is possible to perform the adjustment work without attaching other optical elements only by attaching the semiconductor laser 11 and the beam shaping optical system to the optical case 82. Therefore, the reflection of the rotary polygon mirror 30 is possible. Accurate adjustment is possible without being affected by the error of the optical element located after the surface 31.

  Further, since it is possible to confirm the optical characteristics at an intermediate step of the assembly process of the optical scanning device, it is possible to guarantee the quality step by step and facilitate the work of ensuring the quality of the product.

  Furthermore, since the adjustment operation can be performed only by comparing the optical power passing through the knife edge, a large-scale measuring device that is necessary for measuring the imaging performance on the surface to be scanned 71 becomes unnecessary.

  In addition, since the two knife edges are formed integrally with the optical base 82, the position of the light beam can be accurately adjusted as compared with the case where a jig made of different members is used. .

  Such adjustment of the position of the light beam in the direction orthogonal to the optical axis of the beam shaping optical system can be performed by moving the semiconductor laser 11 or by moving the collimator lens 21. In this embodiment, the semiconductor laser 11 is integrated with the circuit board on which the drive circuit is mounted, and is adjusted by moving it vertically and horizontally in the direction orthogonal to the optical axis. However, the same effect can be obtained by moving the collimator lens 21. Demonstrated.

  In this way, the light beam emitted from the adjusted beam shaping optical system also passes through the reflecting mirror 51, the reflecting mirror 52, and the three folding mirrors of the scanning optical system, which are present in the transmission optical form. Under the influence of the mounting angle accuracy in the sub-scanning direction, the position of incidence on the correction lens 62 in the sub-scanning direction varies.

  In the first embodiment of the present invention, the first reflecting mirror 51 or the second reflecting mirror 52 of the transmission optical system, the first folding mirror 91, the second folding mirror 92 in the scanning optical system, the first The position of the light beam incident on the correction lens 62 is adjusted by rotating any one of the five reflecting mirrors of the third folding mirror 93 within the sub-scanning plane.

  For example, by adjusting the first reflecting mirror 51 by rotating it in the sub-scanning plane, it is not necessary to adjust other reflecting mirrors. In particular, since the first reflecting mirror 51 is closest to the light source among the above five reflecting mirrors, an error in the middle of the optical path can be reduced as compared with the case where the reflecting mirror downstream thereof is adjusted.

  In this way, by adjusting the angle of one of the five reflecting mirrors in the sub-scanning direction with respect to the position of the correction lens 62 in the sub-scanning direction, the other four reflecting mirrors can be adjusted. No need to adjust. Furthermore, it is possible to allow the light beam to be incident on the correction lens 62 at an accurate position in the sub-scanning direction by adjusting only one reflection mirror. Image performance can be obtained.

  Further, since the incident position of the light beam is adjusted in the sub-scanning direction on the correction lens 62 so as to fall within a predetermined range, the spot formed on the scanned surface 71 immediately after the correction lens 62 or its locus The position of the scanning line formed in the sub-scanning direction is also generally set to the normal position.

  Alternatively, in the first embodiment of the present invention, the adjustment of the five reflecting mirrors after the first reflecting surface 31 of the rotary polygon mirror is not performed at all, and the first correction lens 62 is displaced in the sub-scanning direction. Thus, the relative position in the sub-scanning direction with respect to the light beam incident on the correction lens 61 is set within a predetermined range. Since such adjustment can be performed independently at the left and right sides of the correction lens 62, that is, at the start and end of scanning, optimum imaging performance can be obtained independently at the start and end sides. .

  Next, a second embodiment of the present invention will be described.

  FIG. 11 is a layout diagram in the main scanning plane of the second embodiment of the optical scanning device according to the present invention.

  The divergent light beam emitted from the semiconductor laser 11 as the light source is converted into a substantially parallel light beam by the collimator lens 121. Further, the parallel light beam is converted by the shaping lens 122 into a light beam focused in the sub-scanning direction. The rotating polygon mirror 130 is disposed so that the reflecting surface 131 is positioned near the image forming point of the focused light beam in the sub-scanning direction. The collimator lens 121 and the shaping lens 122 constitute a beam shaping optical system.

  The light beam deflected by the reflecting surface 131 is converted into a light beam focused in the main scanning direction by the imaging lens 161. The focused light beam that has exited the imaging lens 161 is converted into a focused light beam in the sub-scanning direction by the correction lens 162, and forms an image on the scanned surface 71 as a spot. Further, in the sub-scanning direction, the refractive power of the correction lens 162 is determined so that the reflecting surface 131 and the scanned surface 71 satisfy an optical conjugate relationship. The surface to be scanned 71 is provided with a scanning object in the same manner as in the first embodiment. These imaging lens 161 and correction lens 162 constitute a scanning optical system.

  Next, the structure of the scanning optical system of the present embodiment in the sub-scan section will be described with reference to FIG. The light beam that has exited the imaging lens 161 is folded back above the rotary polygon mirror 130 by the first folding mirror 191. The folded light beam is further folded by the second folding mirror 192 and enters the correction lens 162. The light beam exiting from the correction lens 162 is finally folded back by the third folding mirror 193 and travels toward the surface to be scanned 71. These three folding mirrors are attached to an optical case 182 that is a container of the optical scanning device.

  In the second embodiment of the present invention, when viewed in the sub-scanning plane including the optical axis of the scanning optical system, (A) the reflection of the rotary polygon mirror 130 of the scanning optical system is reflected on the optical case 182 described later. A part from the surface 131 to the first folding mirror 191 through the imaging lens 161, (B) a part from the first folding mirror 191 to the second folding mirror 192, and (C) from the second folding mirror 193. The optical path is folded in three stages, that is, the part reaching the third folding mirror 193 via the correction lens 162.

  In the second embodiment of the present invention, by adopting such a structure, since the deflection angle of the light beam by the rotary polygon mirror 130 is small, the focal length of the scanning optical system is long, and the reflection surface 131 to the surface to be scanned. Even in an optical scanning device having a long optical path length up to 170, the total length in the optical axis direction of the optical scanning device can be shortened by folding the optical path.

  Further, since the light beam is rotationally deflected in the scanning optical system, as the distance from the reflecting surface 131 of the rotating polygonal mirror 130 increases, the deflection width of the scanned light beam increases and the required width of the folding mirror also increases. I will do it. On the other hand, in the case of the structure as described above, the width of the folding mirror increases as the distance from the bottom surface of the optical case 182 increases. Therefore, when the holding portions are provided on both sides of the folding mirror, the lower side (the bottom surface of the optical case 182). Interference with the lens located on the side) and the scanned light beam.

  Further, since all the folding mirrors are arranged on the surface side of the optical case 182, that is, the side on which the lens group constituting the rotary polygon mirror and the scanning optical system is placed, assembly, adjustment, and inspection work are easy. Therefore, the manufacturing cost is reduced and the reliability of the apparatus is also increased.

  Also in the second embodiment of the optical scanning device of the present invention, the light beam is guided to the light beam detector 163 at a position before scanning the effective scanning region on the surface to be scanned, and the arrival of the light beam is converted into an electric signal. A synchronization signal is obtained by conversion. As the optical scanning device, a required scanning range is from the position of the light beam detector 163 to the rear end of the effective scanning area.

  The light beam traveling toward the light beam detector 163 is separated from the optical path toward the original scanned surface 71 by the separation mirror 164 provided immediately before the correction lens 162, and then passes through the second folding mirror 192. After being converted into a light beam focused in the sub-scanning direction by the beam detection lens 165, the light enters the light beam detector 163. The function of the light beam detection lens 165 is the same as that of the first embodiment, and a description thereof is omitted.

  In the present invention, a shielding plate 166 is provided at a portion positioned upstream of the scanning of the attachment portion of the separation mirror 164 so that the light beam in the lighting period for detecting the arrival of the light beam does not enter the correction lens 162. Is provided.

  In the present invention, as shown in FIG. 11, also in the second embodiment, the surface of the light beam detector 163 is inclined with respect to the incident light beam in the main scanning direction. The reflected light reflected from the surface of the package enclosing the element of the detector 163 or the surface of the element itself is reflected by the second folding mirror 192 and travels toward the shielding plate 166. It does not pass through and reaches the scanned surface 171, and unnecessary irradiation of the scanned surface can be prevented.

  The semiconductor laser 11, the rotary polygon mirror 130, and each lens are attached to the optical case 182. On the extension of the optical axis of the beam shaping optical system, a knife edge (M) 183 formed integrally with the optical case 182 and having an edge parallel to the sub-scanning direction and a knife edge having an edge parallel to the main scanning direction ( S) 184 is provided. Since the structure and operation of these two knife edges and the adjusting method using them are the same as those in the first embodiment, description thereof will be omitted.

  However, since these two knife edges are formed as projections from the bottom surface of the optical case 182, it is not necessary to provide a notch for inserting a sensor for detecting optical power as in the first embodiment.

  As described above, in the present invention, in the second embodiment, similarly to the first embodiment, the semiconductor case 11 and the beam shaping optical system are attached to the optical case 182 and other optical elements are not attached. Since the operation becomes possible, accurate adjustment is possible without being affected by errors of the optical elements of the scanning optical system.

  Further, since it is possible to confirm the optical characteristics at an intermediate step of the assembly process of the optical scanning device, it is possible to guarantee the quality step by step and facilitate the work of ensuring the quality of the product.

  Furthermore, since the adjustment operation can be performed only by comparing the optical power passing through the knife edge, a large-scale measuring device that is necessary for measuring the imaging performance on the surface to be scanned 71 becomes unnecessary.

  Alternatively, since the two knife edges are formed integrally with the optical base 82, the position of the light beam can be accurately adjusted as compared with the case where a jig made of different members is used.

1 is a perspective view showing an overall appearance of an optical scanning device according to a first embodiment of the present invention. It is a perspective view which shows the general appearance drawn except the long lens and the 3rd folding mirror in the optical scanning device in the 1st example of the present invention. FIG. 3 is a plan view in the main scanning plane including the scanning optical system of the optical scanning device according to the first embodiment of the present invention. FIG. 3 is a plan view in the main scanning plane including the transmission optical system of the optical scanning device according to the first embodiment of the present invention. It is sectional drawing in the subscanning surface containing the beam shaping optical system of the optical scanning device in 1st Example of this invention. 2 is a cross-sectional view in the sub-scanning plane including the scanning optical system of the optical scanning device in the first embodiment of the present invention. FIG. FIG. 3 is a development view in the main scanning plane of the transmission optical system of the optical scanning device according to the first embodiment of the present invention. It is a perspective view which shows the relationship between the optical base and optical case of the optical scanning device in 1st Example of this invention. 1 is a perspective view of an optical system that guides a light beam to a light beam detector of an optical scanning device according to a first embodiment of the present invention. It is a top view which shows the circumference | surroundings and rotary shield of the rotary polygon mirror of the optical scanning device in 1st Example of this invention. It is a top view in the main scanning surface of the optical scanning device in 2nd Example of this invention. It is sectional drawing in the subscanning surface containing the scanning optical system of the optical scanning device in 2nd Example of this invention.

Explanation of symbols

  11, 111... Semiconductor laser 21, 121... Collimator lens 22, 122... Shaping lens 30, 130 ・ ・ ・ Rotating polygon mirror, 41, 42, 43. 52... Reflecting mirrors 61 and 161 Imaging lenses 62 and 162... Correction lenses 63 and 163... Light beam detectors 71.・ Optical base, 82, 182 ・ ・ ・ ・ Optical case, 91, 92, 93, 191, 192, 193 ・ ・ ・ ・ Folding mirror

Claims (2)

A light source, a deflector that deflects the light beam emitted from the light source, a scanning optical system that forms an image of the scanning light beam deflected by the deflector on a predetermined surface to be scanned, and the scanning light beam A light beam detector for detecting that the position has been reached, and a separation mirror for directing a scanning light beam to the light beam detector, and the scanning light beam based on a detection signal of the light beam detector. In an optical scanning device that scans a surface to be scanned, a surface of a detection element constituting the light beam detector or a package surface enclosing the element is perpendicular to the light beam incident on the light beam detector in the main scanning plane. The light beam reflected from the surface of the detection element or the surface of the package is shielded by a shielding plate provided on the scanning upstream side of the separation mirror. Optical scanning apparatus according to claim and. The deflector is a rotating polygon mirror having at least a first reflecting surface and a second reflecting surface, deflects a light beam emitted from the light source by the first reflecting surface, and the rotating polygon mirror A transmission optical system for causing the light beam deflected by the first reflecting surface to enter the second reflecting surface of the rotary polygon mirror, and the scanning light beam deflected by the second reflecting surface to be the scanning optics 2. The optical scanning device according to claim 1, wherein scanning is performed by a system.

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