JP2021060565A - Scanning optical device - Google Patents

Abstract

To reduce the displacement of focal positions among a plurality of light sources when there is a change in environment temperature.SOLUTION: A scanning optical device according to one aspect of the present invention includes: a first light source including a first semiconductor laser, a first coupling lens, and a first holder; a second light source including a second semiconductor laser, a second coupling lens, a second holder holding the second semiconductor laser, and a third holder fixed to the second holder and holding the second coupling lens; and a frame. The first light source includes a first substrate fixed to the frame, and the second light source includes a second substrate that is not in contact with the frame. The first holder and the third holder are different in thermal expansion rate.SELECTED DRAWING: Figure 6

Description

The present invention relates to a scanning optical device provided in a laser printer or the like.

Patent Document 1 discloses a scanning optical device (also referred to as a scanner) including a plurality of light sources. In the scanning optical device of Patent Document 1, each light source includes a semiconductor laser and a coupling lens that converts the light emitted from the semiconductor laser into a beam. In such a scanning optical device, each light source may be installed in a different manner from each other in order to reduce the size of the scanning optical device. For example, a scanning optical device may include a light source in which a substrate supporting a semiconductor laser included in the light source is fixed to a frame, and a light source in which the substrate is non-contact with the frame.

JP-A-2009-3944

When the environmental temperature rises, the member connecting the semiconductor laser and the coupling lens expands. In a light source in which the substrate is not fixed to the frame, the distance between the semiconductor laser and the coupling lens changes depending only on the expansion of the member connecting the semiconductor laser and the coupling lens when the ambient temperature rises. On the other hand, in a light source in which the substrate is fixed to the frame, when the ambient temperature rises, the distance between the semiconductor laser and the coupling lens is not only the expansion of the member connecting the semiconductor laser and the coupling lens, but also the frame. It also changes depending on the expansion of the lens. Therefore, when a plurality of light sources have the same configuration as in the technique described in Patent Document 1, when the ambient temperature rises, the light source in which the substrate is fixed to the frame and the light source in which the substrate is not fixed to the frame are not fixed. There is a problem that the distances between the semiconductor laser and the coupling lens are different from each other depending on the light source, and as a result, the focal positions of the respective light sources are different from each other.

One aspect of the present invention is to realize a scanning optical device capable of reducing the deviation of the focal position between a plurality of light sources when the environmental temperature changes.

In order to solve the above problems, the scanning optical device according to one aspect of the present invention includes a first semiconductor laser, a first coupling lens that converts light emitted from the first semiconductor laser into a beam, and the above. A first light source having a first holder that holds the first semiconductor laser and the first coupling lens, a second semiconductor laser, and a second coupling lens that converts light emitted from the second semiconductor laser into a beam. A second light source having a second holder holding the second semiconductor laser and a third holder fixed to the second holder and holding the second coupling lens, the first light source, and the second light source. A deflector that deflects light from the light source, a first scanning optical system that forms an image of light emitted from the first light source and deflected by the deflector on a first image plane, and emitted from the second light source. A second scanning optical system that forms an image of light deflected by a deflector on a second image plane, the first light source, the second light source, the deflector, the first scanning optical system, and the above. The first light source includes a frame that holds the second scanning optical system, the first light source holds the first semiconductor laser, and includes a first substrate fixed to the frame, and the second light source is the second light source. The frame is provided with a second substrate that holds two semiconductor lasers and is not in contact with the frame, and the first holder and the third holder have different thermal expansion rates.

According to the above configuration, since the coefficient of thermal expansion of the first holder and the coefficient of thermal expansion of the third holder are different, the dimensions at which the first holder and the third holder expand when the environmental temperature changes. Is different. As a result, when the environmental temperature changes, the distance between the first semiconductor laser and the first coupling lens changes due to the thermal expansion of the first holder, and the second semiconductor laser and the second coupling lens by the third holder. Can be different from the change in distance. The difference in the change in the distance can offset the change in the distance between the first semiconductor laser and the first coupling lens due to the first substrate being fixed to the frame. As a result, it is possible to reduce the deviation of the focal position between the first light source and the second light source when the environmental temperature changes.

Further, in the scanning optical device according to one aspect of the present invention, the first holder and the second holder are made of metal, and the third holder is made of resin.

According to the above configuration, the coefficient of thermal expansion of the first holder and the coefficient of thermal expansion of the second holder can be made different.

Further, in the scanning optical device according to one aspect of the present invention, the light from the first light source and the light from the second light source are incident on the first scanning optical system and the second scanning optical system. A lens is provided, and the lens is made of resin.

When the ambient temperature of the first light source and the second light source rises, the distances between the first semiconductor laser and the second semiconductor laser and the first coupling lens and the second coupling lens increase, respectively, and the focus is brought to the front. It shifts. According to the above configuration, since the lens is made of resin, it expands when the environmental temperature rises and the focus shifts to the back. As a result, the fluctuation of the focal position can be reduced.

Further, in the scanning optical device according to one aspect of the present invention, the second holder has a first plane portion orthogonal to the emission direction of the second semiconductor laser, and the third holder has the first plane portion. Has a second plane portion in contact with.

According to the above configuration, the distance between the second semiconductor laser and the second coupling lens when the third holder is thermally expanded with reference to the first plane portion of the second holder holding the second semiconductor laser. Fluctuations can be specified.

Further, in the scanning optical device according to one aspect of the present invention, the first plane portion is exposed in a plane facing the second plane portion.

According to the above configuration, when the temperature of the second semiconductor rises, heat can be dissipated from the second semiconductor via the first plane portion.

Further, in the scanning optical device according to one aspect of the present invention, the frame has a side wall orthogonal to the emission direction of the first semiconductor laser, and the first substrate is fixed to the side wall.

According to one aspect of the present invention, it is possible to reduce the deviation of the focal position between a plurality of light sources when the environmental temperature changes.

It is a side sectional view which shows the structure of the color laser printer in this Embodiment which concerns on one Embodiment of this invention. It is a side sectional view which looked at the scanning optical apparatus from the side. It is a figure which looked at the scanning optical apparatus from above. It is an enlarged view around the region where a light source is arranged in a scanning optical apparatus. It is a perspective view of the light source as an example of a 1st light source. It is a perspective view of the light source as an example of the 2nd light source. It is a figure which shows the structural example of a semiconductor laser. It is a figure which shows the incident position in the scanning lens of the light beam group emitted from the light source. It is a figure explaining the interlaced scanning in a scanning optical apparatus. It is a figure which shows the 1st holder provided in the scanning optical apparatus as a modification of the said scanning optical apparatus.

Hereinafter, one embodiment of the present invention will be described in detail. FIG. 1 is a side sectional view showing the configuration of the color laser printer 1 in the present embodiment. In the following description, the direction in which the photoconductor drums 51K, 51C, 51M, and 51Y, which will be described later, are arranged is the front-rear direction, the right side in FIG. 1 is the front side, and the left side is the rear side.

The color laser printer 1 is a horizontal tandem type color laser printer in which a plurality of process units 13 are arranged in parallel along the horizontal direction. In the color laser printer 1, the image is formed in a box-shaped main body casing 2 by a paper feeding unit 4 for feeding the sheet 3, an image forming unit 5 for forming an image on the fed sheet 3, and an image. It is provided with a sheet discharging unit 6 for discharging the formed sheet 3.

The paper feed unit 4 includes a sheet cassette 7 provided at the bottom of the main body casing 2, a paper feed roller 8 provided above the front side of the sheet cassette 7, and a paper feed path 9 provided above the front side of the paper feed roller 8. A pair of transport rollers 10 provided in the middle of the paper feed path 9 and a pair of registration rollers 11 provided at the downstream end of the paper feed path 9 are provided. Sheets 3 are stacked in the sheet cassette 7, and the sheet 3 at the top thereof is sent out to the paper feed path 9 by the rotation of the paper feed roller 8.

In the paper feed path 9, the upstream end is adjacent to the paper feed roller 8 at the bottom so that the sheet 3 is fed forward, and the downstream end is at the top of the transport belt described later. Adjacent to 61, the sheet 3 is formed as a substantially U-shaped transport path such that paper is discharged toward the rear. The sheet 3 sent out to the paper feed path 9 is conveyed by the transfer roller 10 in the paper feed path 9, the transfer direction is reversed in the front-rear direction, and after registration by the registration roller 11, the sheet 3 is rearward by the registration roller 11. The paper is discharged toward.

The image forming unit 5 includes a scanning optical device 12, a process unit 13, a transfer unit 14, and a fixing unit 15.

<Structure of scanning optical device>
Next, the configuration of the scanning optical device 12 will be described with reference to the drawings. The scanning optical device 12 is arranged above the plurality of process units 13 described later in the upper part of the main body casing 2. FIG. 2 is a side sectional view of the scanning optical device 12 as viewed from the side. FIG. 3 is a view of the scanning optical device 12 as viewed from above.

As shown in FIGS. 2 and 3, the scanning optical device 12 includes a frame 16, four light sources 81M / 81K / 81Y / 81C, an incident optical system 18, a polygon mirror 17 as an example of a deflector, and 4 It includes two scanning optical systems 80.

As shown in FIG. 2, the frame 16 has a box shape and is made of resin. The frame 16 holds a polygon mirror 17, four light sources 81M / 81K / 81Y / 81C, an incident optical system 18, and a scanning optical system 80. An exit window 21 corresponding to each color is formed on the bottom wall 43 of the frame 16. The exit windows 21 are provided at different positions in the front-rear direction at different positions at intervals from each other, and from the front to the rear, the yellow exit window 21Y, the magenta exit window 21M, and the cyan exit window sequentially correspond to each color. It is formed as 21C and a black exit window 21K. Hereinafter, the right direction in FIG. 2 will be described as the front direction, and the left direction will be described as the rear direction. The frame 16 includes a bottom wall 43 and a side wall 44 extending from the four peripheral portions of the bottom wall 43 in a direction perpendicular to the bottom wall 43. The frame 16 has a box shape with an open upper portion on the side opposite to the process portion 13. Although not shown, the upper portion of the frame 16 is covered with a separate cover.

One polygon mirror 17 is provided on the motor substrate 22 at the center of the frame 16 in the front-rear direction with respect to the four light sources 81 described later. As shown in FIG. 3, the polygon mirror 17 is formed on a polyhedron having a plurality of beam deflection surfaces 17a (a hexahedron in the present embodiment), and the motor substrate 22 is centered on a rotation shaft 23 provided at the center thereof. It is rotationally driven at high speed by the power of the scanner motor housed inside.

The scanning optical device 12 in this embodiment includes four light sources 81. In the following description, when the four light sources are distinguished, the light source 81 is referred to as a light source 81M, a light source 81K, a light source 81Y, and a light source 81C. The light source 81M and the light source 81K are examples of the first light source, and the light source 81Y and the light source 81C are examples of the second light source.

The light source 81M and the light source 81K are arranged side by side in the front-rear direction of the main body casing 2. The light source 81Y and the light source 81C are arranged so as to face each other in the front-rear direction of the main body casing 2. The beams emitted from the light source 81M and the light source 81K are substantially orthogonal to the beams emitted from the light source 81Y and the light source 81C. The four light sources 81 emit beams toward the polygon mirror 17.

FIG. 4 is an enlarged view of the periphery of the region where the light source 81 is arranged in the scanning optical device 12. FIG. 5 is a perspective view of the light source 81M. As shown in FIGS. 4 and 5, the light source 81M includes a semiconductor laser 101M as an example of a first semiconductor laser, a coupling lens 102 as an example of a first coupling lens, and a holder as an example of a first holder. A 103 and a substrate 104 as an example of the first substrate are provided. In the light source 81M, the semiconductor laser 101M and the coupling lens 102 are held by the holder 103. The light source 81M converts the laser light emitted from the semiconductor laser 101M into a beam by the coupling lens 102.

The holder 103 is a member formed by sheet metal processing of a plate material made of an aluminum alloy. As shown in FIG. 5, the holder 103 includes a laser holding wall 111 to which the semiconductor laser 101M is fixed, a trapezoidal lens holding portion 112 to which the coupling lens 102 is fixed, and a laser holding wall 111 and a lens holding portion 112. It is provided with a connecting portion 113 for connecting to and.

The laser holding wall 111 is formed with a circular mounting hole formed through the center of the laser holding wall 111 so that the semiconductor laser 101M can be fitted. A edging 114 is formed on the edge of the mounting hole so as to project in the direction in which the laser beam of the semiconductor laser 101M is emitted. The edging 114 forms a tubular portion that fits with the semiconductor laser 101M. Further, the laser holding wall 111 is provided with two screw holes 115 for fixing the semiconductor laser 101M to the substrate 104 described later.

The lens holding portion 112 is arranged in front of the laser holding wall 111 at a predetermined distance. A groove 112a extending in the direction in which the laser beam of the semiconductor laser 101M is emitted is formed on the upper surface of the lens holding portion 112, that is, the surface on which the coupling lens 102 is attached. The groove 112a serves as a portion for arranging the photocurable resin 135, which is an adhesive for fixing the coupling lens 102 to the lens holding portion 112. That is, by applying the photocurable resin 135 in a form in which the photocurable resin 135 is accumulated in the groove 112a, it is possible to prevent the resin from flowing around the lens and to use it as a reference for the position where the photocurable resin 135 is applied. Can be done.

The connecting portion 113 includes a lower wall 113a extending forward from the lower end of the laser holding wall 111, and a front wall 113b extending vertically so as to connect the front end of the lower wall 113a and the rear end of the lens holding portion 112. ing. The lower wall 113a is formed with screw holes 116 for fixing the holder 103 to the frame 16.

The substrate 104 is a printed circuit board for controlling the operation of the semiconductor laser 101M. The substrate 104 holds the semiconductor laser 101M and the semiconductor laser 101K. As shown in FIG. 4, the substrate 104 is fixed to the outside of the side wall 44 of the frame 16. The side wall 44 is orthogonal to the emission direction of the semiconductor laser 101M.

The light source 81K has the same configuration as the light source 81M except that the semiconductor laser 101K is provided in place of the semiconductor laser 101M. The difference between the semiconductor laser 101M and the semiconductor laser 101K will be described later.

FIG. 6 is a perspective view of the light source 81C. In FIG. 6, the coupling lens 105, which will be described later, is not shown. As shown in FIGS. 4 and 6, the light source 81C includes a semiconductor laser 101C as an example of a second semiconductor laser, a coupling lens 105 as an example of a second coupling lens, and a holder as an example of a second holder. It includes 106, a holder 107 as an example of a third holder, and a substrate 108 as an example of a second substrate. In the light source 81C, the semiconductor laser 101M is held by the holder 106, and the coupling lens 105 is held by the holder 107. The light source 81C converts the laser light emitted from the semiconductor laser 101C into a beam by the coupling lens 105.

The holder 106 holds the semiconductor laser 101C. The holder 106 is a flat plate made of an aluminum alloy. The holder 106 is formed with a circular mounting hole (not shown) formed through the holder 106 so as to fit the semiconductor laser 101C in the center thereof. A edging 120 is formed on the edge of the mounting hole so as to project in the direction in which the laser beam of the semiconductor laser 101C is emitted. The edging 120 forms a tubular portion that fits with the semiconductor laser 101C. Further, the holder 106 is provided with two screw holes (not shown) for fixing the semiconductor laser 101C to the substrate 108 described later. The holder 106 has a first plane portion 106a orthogonal to the emission direction of the semiconductor laser 101C on the holder 107 side.

The holder 107 holds the coupling lens 105. The holder 107 includes a lens holding portion 121, a flat plate portion 122, and a connecting portion 123. The lens holding portion 121, the flat plate portion 122, and the connecting portion 123 are made of resin.

The lens holding portion 121 has a trapezoidal shape to which the coupling lens 105 is fixed. The lens holding portion 121 is arranged in front of the holder 106 at a predetermined distance. A groove 121a extending in the direction in which the laser beam of the semiconductor laser 101C is emitted is formed on the upper surface of the lens holding portion 121, that is, the surface on which the coupling lens 105 is attached.

The flat plate portion 122 has a second flat surface portion 122a that contacts the first flat surface portion 106a of the holder 106. The flat plate portion 122 is formed with screw holes (not shown) for connecting the flat plate portion 122 and the holder 106, and the flat plate portion 122 and the holder 106 are fastened with screws.

The second plane portion 122a has a notch in a part of the upper portion when viewed from the emission direction of the semiconductor laser 101C. As a result, a part of the first plane portion 106a of the holder 106 can be exposed to the outside in the plane facing the second plane portion 122a. As a result, the heat dissipation effect of the semiconductor laser 101C via the first flat surface portion 106a can be improved. In this embodiment, since the holder 106 having the first flat surface portion 106a is made of metal, the heat dissipation is high.

The connecting portion 123 connects the lens holding portion 121 and the flat plate portion 122. A screw hole 123a for fixing the holder 107 to the frame 16 is formed on the lower wall of the connecting portion 123.

The substrate 108 is a printed circuit board for controlling the operation of the semiconductor laser 101C. The substrate 108 holds the semiconductor laser 101C. The substrate 108 is in non-contact with the frame 16.

The light source 81Y has the same configuration as the light source 81C except that the semiconductor laser 101Y is provided instead of the semiconductor laser 101C. The difference between the semiconductor laser 101C and the semiconductor laser 101Y will be described later.

As shown in FIG. 4, the incident optical system 18 includes a slit plate 26, a reflection mirror 27, and a cylindrical lens 29. The slit plate 26 is formed of a substantially L-shaped plate in which two flat plates are continuous in a substantially right angle direction, and each flat plate has a slit. Each slit is formed in an elongated hole shape extending in the main scanning direction, and is arranged at intervals corresponding to each light source 81 in the sub-scanning direction. The slit plate 26 is arranged so that each slit is arranged on the downstream side of each of the coupling lenses 102 and 105 in the passing direction of the laser beam and faces each of the coupling lenses 102 and 105, respectively. ..

Each laser beam that has passed through the coupling lenses 102 and 105 is restricted in cross-sectional shape orthogonal to the passing direction of the laser beam by each slit of the slit plate 26, whereby the laser beam emitted from each light source 81 is lightened. Stray light is prevented.

The reflection mirror 27 is arranged on the downstream side of each of the slits in the passing direction of the laser beam, and is provided so as to be inclined at approximately 45 ° with respect to each flat plate of the substantially L-shaped slit plate 26. There is. In this reflection mirror 27, the laser light emitted from the light source 81K and the light source 81M passes linearly on the upper side as it is, and the laser light emitted from the light source 81Y and the light source 81C is reflected by approximately 90 ° on the lower side. It is formed to do. As a result, the optical paths of the two laser beams emitted from the two light sources 81 in the directions orthogonal to each other are combined so as to coincide with each other in the main scanning direction.

The cylindrical lens 29 is a resin lens formed by injection molding using a resin material, and is a slit plate 26 on the downstream side of the slit plate 26 and on the upstream side of the polygon mirror 17 in the passing direction of the laser beam. And are arranged facing each other at a predetermined interval. In this cylindrical lens 29, the surface facing the slit plate 26 is a cylindrical incident surface on which the laser light passing through the slit plate 26 is incident, and the surface facing the polygon mirror 17 is incident from the incident surface. It is a flat exit surface that emits the laser light.

The polygon mirror 17 deflects two sets (four) of laser beams incident from opposite sides by high-speed rotation, and scans them in the main scanning direction. Since the two laser beams in each set are incident on the reflection surface of the polygon mirror 17 at different angles, they are gradually reflected from the beam deflection surface 17a at angles separated from each other in the sub-scanning direction.

In the scanning optical device 12, four scanning optical systems 80M, 80K, 80Y, and 80C are provided corresponding to each color in FIG. 2. Each scanning optical system 80 includes a scanning lens 19 as an example of a lens and a plurality of mirrors. Details of the scanning optical system 80 for each color will be described later. In the scanning optical system 80, the scanning lens 19 converts the beam deflected by the polygon mirror 17 at a constant angular velocity so as to scan the image plane at a constant velocity, and forms an image in the main scanning direction. Further, in the scanning optical system 80, the beam deflection surface 17a of the polygon mirror 17 is imaged on the image surface in the sub-scanning direction by the scanning lens 19, and an error in the parallelism of the mirror surface with respect to the rotation axis of the polygon mirror 17 (that is, that is). Correct the trouble of the deflector). The scanning lens 19 converts two laser beams incident on the polygon mirror 17 from the incident optical system 18 and deflected by the polygon mirror 17 at a constant angular velocity in the main scanning direction so as to scan the image plane at a constant velocity. It is a lens having fθ characteristics. The scanning lens 19 is made of resin.

The scanning optical system 80Y corresponding to yellow forms an image of the light emitted from the light source 81Y and deflected by the polygon mirror 17 on the photosensitive drum 51Y as an example of the second image plane. The scanning optical system 80Y is an example of the second scanning optical system. The scanning optical system 80Y is arranged at the foremost position in the front-rear direction, and combines one scanning lens 19, a mirror 35a that reflects the laser beam that has passed above the scanning lens 19, and the laser beam that is reflected by the mirror 35a. As an example of the second image plane, a mirror 35b that reflects toward the photosensitive drum 51Y is provided.

In the scanning optical system 80Y, the laser beam passes above the one scanning lens 19 and is reflected obliquely rearward and upward by the mirror 35a, and is reflected downward in the vertical direction by the mirror 35b and emitted from the yellow exit window 21Y.

The scanning optical system 80M corresponding to magenta forms an image of the light emitted from the light source 81M and deflected by the polygon mirror 17 on the photosensitive drum 51M as an example of the first image plane. The scanning optical system 80M is an example of the first scanning optical system. The scanning optical system 80M is arranged between the polygon mirror 17 and the scanning optical system 80Y, and includes one scanning lens 19 and two mirrors 37a that reflect the laser light that has passed under the scanning lens 19. It includes a 37b and a mirror 37c that reflects the laser beam reflected by the mirror 37b toward the photosensitive drum 51M.

In the scanning optical system 80M, the laser beam passes under one of the scanning lenses 19 and is reflected upward at the mirror 37a, then backward at the mirror 37b, and reflected downward at the mirror 37c in the vertical direction. It is emitted from the exit window 21M.

The scanning optical system 80C corresponding to cyan images the light emitted from the light source 81C and deflected by the polygon mirror 17 on the photosensitive drum 51C as an example of the second image plane. The scanning optical system 80C is an example of the second scanning optical system. The scanning optical system 80C is arranged between the polygon mirror 17 and the scanning optical system 80K corresponding to black, which will be described later, and reflects the other scanning lens 19 and the laser light that has passed under the scanning lens 19. The two mirrors 39a and 39b are provided, and the mirror 39c that reflects the laser light reflected by the mirror 39b toward the photosensitive drum 51C is provided.

In the scanning optical system 80C, the laser beam passes under the other scanning lens 19 and is reflected upward at the mirror 39a, then forward at the mirror 39b, and then vertically downward at the mirror 39c. It is emitted from the cyan emission window 21C.

The scanning optical system 80K corresponding to black forms an image of the light emitted from the light source 81K and deflected by the polygon mirror 17 on the photosensitive drum 51K as an example of the first image plane. The scanning optical system 80K is an example of the first scanning optical system. The scanning optical system 80K is arranged at the rearmost position in the front-rear direction, and combines the other scanning lens 19, the mirror 41a that reflects the laser light that has passed above the scanning lens 19, and the laser light that is reflected by the mirror 41a. It is provided with a mirror 41b that reflects toward the photosensitive drum 51K.

In the scanning optical system 80K, the laser beam passes above the other scanning lens 19, is reflected obliquely forward and upward by the mirror 41a, is reflected downward in the vertical direction by the mirror 41b, and is emitted from the black exit window 21K.

Here, in the scanning optical device 12 of the present embodiment, the substrate 104 is fixed to the side wall 44 of the frame 16 in the light source 81K and the light source 81M. Therefore, when the environmental temperature rises, the distance between the semiconductor laser 101K / 101M and the coupling lens 102 is not only the expansion of the holder 103 connecting the semiconductor laser 101K / 101M and the coupling lens 102, but also the expansion of the frame 16. It also depends on. Specifically, when the environmental temperature rises, as shown in FIG. 4, the frame 16 expands so that the distance between the screw hole 116, which is the fixing portion of the holder 103 to the frame 16, and the substrate 104 increases. To do. As a result, the distance D between the semiconductor 101 laser K / 101M and the coupling lens 102 becomes large.

On the other hand, in the light source 81C and the light source 81Y, the substrate 108 is not fixed to the frame 16. Therefore, when the environmental temperature rises, the distance between the semiconductor lasers 101C / 101Y and the coupling lens 105 changes depending only on the expansion of the holder 107 connecting the semiconductor lasers 101C / 101Y and the coupling lens 105.

Therefore, as in the conventional case, when the holder connecting the semiconductor laser and the coupling lens is made of the same material in all the light sources, the semiconductor laser in the light source in which the substrate is fixed to the frame made of resin. The distance between the semiconductor laser and the coupling lens becomes larger than the distance between the semiconductor laser and the coupling lens in a light source in which the substrate is not fixed to the frame. As a result, the focal positions of the light source fixed to the frame and the light source whose substrate is not fixed to the frame are different from each other.

On the other hand, in the scanning optical device 12 of the present embodiment, the holder 103 of the light source 81K and the light source 81M is made of metal, and the holder 107 of the light source 81Y and the light source 81C is made of resin. Therefore, the coefficient of thermal expansion of the holder 107 is higher than the coefficient of thermal expansion of the holder 103. As a result, when the environmental temperature rises, the holder 107 can be expanded more than the holder 103. In other words, when the environmental temperature changes, the distance between the semiconductor lasers 101K / 101M and the coupling lens 102 changes due to the thermal expansion of the holder 103, and the semiconductor lasers 101Y / 101C and the coupling lens due to the thermal expansion of the holder 107. The change in distance from 105 can be different. The difference in the change in the distance can offset the change in the distance between the semiconductor laser and the coupling lens due to the substrate 104 being fixed to the frame 16. As a result, it is possible to reduce the deviation of the focal position between the light sources 81K / 81M and the light sources 81C / 81Y when the environmental temperature changes.

Here, when the environmental temperature of the light source 81 rises, the distance between the semiconductor laser and the coupling lens increases, and the focus shifts toward the front. In the scanning optical device 12, the scanning optical system 80 includes a scanning lens 19 made of resin, in which light from light sources 81K / 81M and light from light sources 81C / 81Y are both incident. As a result, when the environmental temperature rises, the scanning lens 19 made of resin expands and the focal point shifts to the back side, so that the fluctuation of the focal position can be reduced.

Further, in the scanning optical device 12, the holder 106 has a first plane portion 106a orthogonal to the emission direction of the semiconductor lasers 101C / 101Y, and the holder 107 has a second plane portion 122a in contact with the first plane portion 106a. Have.

Thereby, the fluctuation of the distance between the semiconductor laser 101C / 101Y and the coupling lens 105 when the holder 107 is thermally expanded is defined with reference to the first plane portion 106a of the holder 106 holding the semiconductor laser 101C / 101Y. can do.

Next, the details of the semiconductor lasers 101K / 101M / 101C / 101Y in this embodiment will be described.

In the scanning optical device 12 of the present embodiment, an interlacing operation is performed for each scanning. Therefore, the semiconductor lasers 101K, 101M, 101C, and 101Y each include a plurality of light emitting units, and in the present embodiment, two light emitting units.

Here, first, the semiconductor laser 101M will be described. FIG. 7 is a diagram showing the configuration of the semiconductor laser 101M. As shown in FIG. 7, the semiconductor laser 101M has two light emitting units E1 and E2. The light emitting units E1 and E2 are arranged so as to be separated by a distance So. In the semiconductor laser 101M of the present embodiment, the two light emitting units E1 and E2 are separated by a distance So = 30 μm.

The line L1 connecting the two light emitting portions E1 and E2 is oblique with respect to the main scanning direction. In this example, the angle θ formed by the line L1 and the main scanning direction is 78.85 °. As a result, the distance Po in the sub-scanning direction of the light emitting units E1 and E2 becomes Po = So × sinθ = 29.43 μm. Further, the interval Qo of the light emitting units E1 and E2 in the main scanning direction is Qo = So × cos θ = 5.80 μm. Since the imaging magnification of the scanning optical system 80M in the sub-scanning direction is 4.3 times, the distance P between the two beam spots imaged on the photosensitive drum 51M in the sub-scanning direction is P = Po × βs = 127 μm. Become.

In the scanning optical device 12, the angle formed by the line connecting the two light emitting portions and the main scanning direction in the semiconductor lasers 101M and 101C is 78.85. Further, in the semiconductor lasers 101K and 101Y, the angle formed by the line connecting the two light emitting portions and the main scanning direction is −78.85.

FIG. 8 is a diagram showing an incident position of the light beam group emitted from the light source 81K in the scanning lens 19. The left-right direction in the figure represents the main scanning direction, and the vertical direction in the figure represents the sub-scanning direction. Further, in the figure, "SOS" represents the scanning start position, "COS" represents the scanning center position, and "EOS" represents the scanning end position.

As shown in FIG. 8, at the COS position, the incident height H1 of the main ray of the light beam from the light emitting portion E1 shown by the solid line in the light beam group and the main ray of the light beam from the light emitting portion E2 shown by the broken line. The ratio to the incident height H2 is about 1.32: 1.

The semiconductor lasers 101K and 101Y in the light source 81K and the light source 81Y emit light because the angle formed by the line connecting the two light emitting portions and the main scanning direction is −78.85 °, which is opposite to that of the semiconductor laser 101M. The positional relationship of the points is reversed. Since the angle formed by the line connecting the two light emitting portions and the main scanning direction of the semiconductor laser 101C in the light source 81C is the same as that of the semiconductor laser 101M, the positional relationship of the light emitting points is also the same as that of the light source 81M.

FIG. 9 is a diagram illustrating interlaced scanning in the scanning optical device 12, and shows the movement of the images IE1 and IE2 of the light emitting portions E1 and E2 on the scanned surface of the photosensitive drum 51K, respectively. In the illustrated example, a plurality of scanning lines separated from each other in the sub-scanning direction based on the laser light from the light emitting units E1 and E2 described above are exposed.

Specifically, for example, at a certain timing, the image IE1 of the light emitting unit E1 and the image IE2 of the light emitting unit E2 are scanned in the main scanning direction along the scanning lines S11 and S14, respectively. In this example, the distance between the centers of the image IE1 and the image IE2 in the sub-scanning direction corresponds to the pitch P of the light beam group irradiated from the light source 81K, and is between the centers of the scanning lines S11, S12, S13 ... It is 3 times the distance Pi.

On the other hand, the photosensitive drum 51K is rotationally driven by a motor (not shown). The surface to be scanned of the photosensitive drum 51K on which the light beam group is scanned moves by Pm in the sub-scanning direction while the images IE1 and IE2 are scanned once in the main scanning direction as described above. This distance Pm is twice the distance Pi. Therefore, for example, after the images IE1 and IE2 scan the scanning lines S11 and S14 as shown at the timing shown in the figure, the images IE1 and IE2 are displaced by two scanning lines S13 and S16 as shown by the alternate long and short dash line. To scan. Then, at the next timing, the images IE1 and IE2 scan the scanning lines S15 and S18 which are further displaced by two lines. After that, the same scanning mode is repeated.

In the present embodiment, as described above, scanning with the nth scanning line Sn and n + third scanning line Sn + 3 (where n is a natural number) is executed for each scan by the light beam group in the sub-scanning direction. Will be done. As a result, exposure is sequentially performed along all the scanning lines S of the surface to be scanned 61a.

<Modification example>
In the above embodiment, the holder 103 is provided for each of the light source 81M and the light source 81K, but the scanning optical device of the present invention is not limited to this. FIG. 10 is a diagram showing a holder 103A included in the scanning optical device in this modified example. As shown in FIG. 10, the scanning optical device in this modification includes a holder 103A in which the holder 103 of the light source 81M and the holder 103 of the light source 81K are integrally formed in the above embodiment. Holder 103A is an example of the first holder.

The holder 103A is made of metal. The holder 103A holds a semiconductor laser 101M, a semiconductor laser 101K, and a coupling lens (not shown in FIG. 10) corresponding to the semiconductor laser 101M and the semiconductor laser 101K, respectively.

<Structure of image forming part>
As shown in FIG. 1, a plurality of process units 13 are provided corresponding to toners of a plurality of colors. That is, the process unit 13 is composed of four parts: a yellow process unit 13Y, a magenta process unit 13M, a cyan process unit 13C, and a black process unit 13K. These process units 13 are sequentially arranged in parallel from the front to the rear with a distance from each other. Each process unit 13 includes a photosensitive drum 51, a charger 52, and a developing cartridge 53.

The photosensitive drum 51 has a cylindrical shape, and the outermost surface layer is formed of a positively charged photosensitive layer made of polycarbonate or the like to form an image plane. It has a drum shaft that extends along.

The charger 52 includes a wire and a grid, and a positively charged scorotron type charger that generates a corona discharge by applying a charging bias can be used so as not to come into contact with the photosensitive drum 51 behind the photosensitive drum 51. They are arranged facing each other at intervals.

The developing cartridge 53 includes a developing roller 56, a supply roller 57, and a layer thickness regulating blade 58 in its housing. The upper portion of the housing of the developing cartridge 53 is formed as a toner accommodating chamber 55 for accommodating toner, and toner of each color is accommodating.

At the time of image formation, each process unit 13 supplies toner of each color stored in each toner storage chamber 55 to the supply roller 57, and is supplied to the developing roller 56 by rotation of the supply roller 57. At this time, the toner is positively triboelectrically charged between the supply roller 57 and the developing roller 56 to which the developing bias is applied. The toner supplied onto the developing roller 56 enters between the layer thickness regulating blade 58 and the developing roller 56 as the developing roller 56 rotates, and becomes a thin layer having a constant thickness on the developing roller 56. It is carried on.

On the other hand, the charger 52 generates a corona discharge by applying a charging bias to uniformly positively charge the surface of the photosensitive drum 51. The surface of the photosensitive drum 51 is uniformly positively charged by the charger 52 as the photosensitive drum 51 rotates, and then exposed by high-speed scanning of the laser beam emitted from the exit window 21 of the scanning optical device 12. Electrostatic latent images of each color corresponding to the image to be formed on the sheet 3 are formed.

Further rotation of the photosensitive drum 51 causes the toner carried on the surface of the developing roller 56 and to be positively charged to come into contact with the photosensitive drum 51 due to the rotation of the developing roller 56. The electrostatic latent image formed on the surface, that is, the surface of the photosensitive drum 51 that is uniformly positively charged, is supplied to the exposed portion exposed by the laser beam and whose potential is lowered. As a result, the electrostatic latent image of the photosensitive drum 51 is visualized, and a toner image by reverse development is supported on the surface of the photosensitive drum 51 corresponding to each color.

The transfer unit 14 is arranged in the main body casing 2 above the sheet cassette 7 and below the process unit 13 along the front-rear direction. The transfer unit 14 includes a drive roller 59, a driven roller 60, a conveyor belt 61, a transfer roller 62, and a belt cleaning unit 63.

The belt cleaning unit 63 is below the transport belt 61 and is the black process unit 1.
They are arranged so as to face each other with the transport belt 61 sandwiched between 3K. The belt cleaning unit 63 includes a primary cleaning roller 64, a secondary cleaning roller 65, a scraping blade 66, and a cleaning box 67.

The sheet ejection unit 6 includes a paper ejection pass 71, a paper ejection roller 72, and a paper ejection tray 73. In the paper ejection path 71, the upstream end is adjacent to the transport roller 70 at the bottom so that the sheet 3 is fed backward, and the downstream end is at the paper ejection roller 72 at the top. Adjacent to each other, the sheet 3 is formed as a transport path for the substantially U-shaped sheet 3 so that the sheet 3 is discharged toward the front. The paper ejection rollers 72 are provided as a pair of rollers at the downstream end of the paper ejection path 71. The output tray 73 is formed on the upper surface of the main body casing 2 as an inclined wall that inclines downward from the front to the rear.

The sheet 3 sent from the transport roller 70 is ejected forward by the paper eject roller 72 after the conveying direction is reversed in the paper ejection path 71. The ejected sheet 3 is placed on the output tray 73.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

12 Scanning optics 16 frames 17 Polygon mirror (deflector)
19 Scanning lens (lens)
44 Side wall 80M, 80K scanning optical system (first scanning optical system)
80C, 80Y scanning optical system (second scanning optical system)
81M, 81K light source (first light source)
81C, 81Y light source (second light source)
101M, 101K semiconductor laser (first semiconductor laser)
101C, 101Y semiconductor laser (second semiconductor laser)
102 Coupling lens (1st coupling lens)
104 board (first board)
103, 103A holder (first holder)
105 Coupling Lens (2nd Coupling Lens)
106 holder (second holder)
106a First flat surface 107 holder (third holder)
108 board (second board)
122a 2nd plane

Claims (6)

A first holder having a first semiconductor laser, a first coupling lens that converts light emitted from the first semiconductor laser into a beam, and a first holder that holds the first semiconductor laser and the first coupling lens. 1 light source and
The second semiconductor laser, the second coupling lens that converts the light emitted from the second semiconductor laser into a beam, the second holder that holds the second semiconductor laser, and the second holder that is fixed to the second holder. A second light source with a third holder that holds the coupling lens,
A deflector that deflects light from the first light source and the second light source,
A first scanning optical system that forms an image of light emitted from the first light source and deflected by the deflector on a first image plane.
A second scanning optical system that forms an image of the light emitted from the second light source and deflected by the deflector on the second image plane.
A frame that holds the first light source, the second light source, the deflector, the first scanning optical system, and the second scanning optical system is provided.
The first light source holds the first semiconductor laser and includes a first substrate fixed to the frame.
The second light source holds the second semiconductor laser and includes a second substrate that does not contact the frame.
A scanning optical device in which the first holder and the third holder have different coefficients of thermal expansion. The first holder and the second holder are made of metal.
The scanning optical device according to claim 1, wherein the third holder is a resin. The first scanning optical system and the second scanning optical system include a lens in which both the light from the first light source and the light from the second light source are incident.
The scanning optical device according to claim 1 or 2, wherein the lens is made of a resin. The second holder has a first plane portion orthogonal to the emission direction of the second semiconductor laser.
The scanning optical device according to any one of claims 1 to 3, wherein the third holder has a second flat surface portion in contact with the first flat surface portion. The scanning optical device according to claim 4, wherein the first flat surface portion is exposed in a plane facing the second flat surface portion. The frame has a side wall orthogonal to the emission direction of the first semiconductor laser.
The scanning optical device according to any one of claims 1 to 5, wherein the first substrate is fixed to the side wall.

Images