JPH04340914A - Optical scanning device - Google Patents

Abstract

PURPOSE:To easily position and precisely and stably arrange the optical scanning device on an optical housing by providing a holder with positioning holes and the optical housing with plural positioning projections and engaging them. CONSTITUTION:A couple of left and right positioning holes 29 and a couple of left and right fitting holes 30 are provided at the horizontal part 27a of the holder 27 of a light source unit 20 and a couple of left and right positioning holes 31 and a couple of left and right fitting holes 32 are provided even at the vertical part 27b. The side wall 34 of the optical housing 33, on the other hand, has a couple of positioning holes 36 and a couple of fitting screw holes 37 at both left and right sides of a cut window part 35. The positioning projections 36 of the optical housing are fitted in the positioning holes 31 of a light source unit 20 to determine the laser projection position of the light source unit 20, and fitting screws 41 are screwed in the fitting screw holes 37 through the fitting screws 32 to fix the light source unit to the side wall 34.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used in a laser beam printer, a digital copying machine, a laser beam facsimile, etc., and more particularly to a mounting structure for mounting a light source unit and an imaging lens therein to an optical housing.

0002

[Prior Art] In an optical scanning device using a semiconductor laser,
A semiconductor laser and its holder, and a coupling lens and its holding part are integrated to form a light source unit, and this is arranged in a predetermined combination with other optical elements, such as an f-theta lens that is an imaging lens, a cylindrical lens, etc., to produce an optical system. It is designed to be attached to the housing.

FIG. 10 shows a conventional general light source unit mounting structure, where 1 is a light source unit and 2 is an optical housing. The light source unit 1 includes a semiconductor laser and a coupling lens built into a cylindrical lens barrel 4 protruding from a vertical plate-shaped holder 3. Side wall 5 of optical housing 2
A light source unit positioning hole 6 is provided in the. In the light source unit 1, the lens barrel 4 is fitted into the light source unit positioning hole 6 to position the laser emission position, and the front surface of the holder 3 is brought into contact with the outer surface of the side wall 5 in the optical axis direction. It was positioned and fixed to the side wall 5 with mounting screws 7. Note that the lens barrel 4 of the light source unit 1 is
In some cases, it is fitted into a U-shaped positioning recess as described in Japanese Patent No. 4919.

By the way, the optical housing 2 needs to be made of a material with high rigidity and a coefficient of thermal expansion as low as possible in order to maintain the arrangement relationship of the optical elements, and in order to reduce weight and cost, it is made of glass. They are often molded from fiber-reinforced resin, aluminum die-casting, etc., and recently they are often molded not only for arranging optical components, but also integrally with other structural members. For this reason, it may be difficult to provide a light source unit positioning hole 6 or a recess in the side wall 5 of the optical housing 2 to fit and position the lens barrel 4 of the light source unit 1 due to the structure of the mold. . In such a case, the shape of the holder and lens barrel of the light source unit 1 must be changed, and even if the light source unit has exactly the same focal position relationship between the semiconductor laser light source and the coupling lens, the mounting adjustment structure must be changed. Cannot be used in common. The light source unit requires precise adjustment, so
In the first place, an expensive adjustment device is required, and not being able to use it in common increases costs.

In the case of FIG. 10, since the outer diameter of the lens barrel 4 of the light source unit 1 and the position of the hole for the mounting screw 7 are determined, the optical housing 2 to which the light source unit 1 is attached is fixed.
There were restrictions on the layout.

On the other hand, regarding the imaging lens (fθ lens), in the conventional optical scanning device, as shown in FIG. 11, a rectangular imaging lens 8 as shown in FIG. was installed as follows. That is, as shown in the figure, the reference surface 8a of the imaging lens 8 is connected to the mounting reference surface 9 of the optical housing, and both end surfaces 8b of the imaging lens 8 are connected to a pair of positioning protrusions provided on the optical housing. A pair of plate springs 12 are attached to both protrusions 10 with setscrews 11, and both ends of the imaging lens 8 are pressed and fixed by these plate springs 12.

By the way, imaging lenses have conventionally been formed by polishing optical glass, but the processing process is complicated and requires a long time, and the cost is high, so in recent years,
With advances in high-precision molding technology, imaging lenses are increasingly being made of plastic. The material used is transparent resin such as polycarbonate resin or acrylic resin.
If impurities are mixed in, the optical properties will deteriorate significantly, so materials with high purity are selected. Therefore, an imaging lens made of resin generally has low rigidity and a high coefficient of thermal expansion.

Although the imaging lens itself has such problems, if it is fixed with a leaf spring as described above, stress will be applied directly to the imaging lens itself, causing it to deform. As for fixing the image lens, a fixing method that does not apply stress, such as adhesion, is preferable. However, even in this case, problems such as lens deformation or adhesive peeling due to differences in thermal expansion coefficient due to environmental temperature changes cannot be avoided. In addition, in an imaging lens composed of multiple lenses,
It is also conceivable that axial misalignment between the lenses will occur, and that the imaging characteristics will change.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a light source unit and an imaging lens in view of the above-mentioned problems in mounting the light source unit and fixing and thermal problems of the imaging lens. The object is to enable easy and stable placement on an optical housing with good positioning accuracy.

0010

[Means for Solving the Problems] Regarding the attachment of a light source unit to an optical housing, the present invention provides a plurality of positioning protrusions on one of the holder of the light source unit and the optical housing, and a plurality of positioning holes on the other. The light source unit is attached to the optical housing by fitting the positioning protrusion and the positioning hole.

Regarding the attachment of the imaging lens to the optical housing, a positioning protrusion is provided on the mounting reference surface of the imaging lens on its center line, and a positioning hole is provided in the optical housing, and these positioning protrusions and positioning holes are connected to each other. The imaging lens is fitted onto the optical housing.

0012

[Operation] Regarding the mounting of the light source unit, the positioning can be performed with high accuracy regardless of the shape of the light source unit mounting portion on the optical housing side.

Regarding the mounting of the imaging lens, the optical axis of the lens is always maintained and it can be held in the optical housing without restricting the longitudinal expansion and contraction of the lens end, so stress due to temperature changes cannot occur. , the influence on optical properties can also be minimized.

[0014]

Embodiments Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an optical scanning device according to the present invention. A laser beam L emitted from a light source unit 20 is shaped by an aperture 21 and then enters a rotating polygon mirror 22 which is a deflector. The laser beam deflected by the rotating polygon mirror 22 passes through an imaging lens 23 and a reflecting mirror 24.
A spot image is formed on the photoreceptor 26 through the cylindrical lens 25.

FIG. 2 shows an embodiment in which the present invention is applied to a light source unit 20. As shown in the figure, the holder 27 of the light source unit 20 has an L-shaped plate shape consisting of a horizontal part 27a and a vertical part 27b, and has a lens barrel 28 protruding from the center of the front of the vertical part 27b. A semiconductor laser and a coupling lens are arranged in the lens barrel 28 in a known manner. The horizontal portion 27a is provided with a pair of left and right positioning holes 29 and a pair of left and right mounting holes 30, and the vertical portion 27b is also provided with a pair of left and right positioning holes 31 and a pair of left and right mounting holes 32.
is provided.

On the other hand, a cutout window 35 is provided in the side wall 34 of the optical housing 33. The width of this notched window portion 35 is such that the lens barrel 28 of the light source unit 20 has a sufficient margin (gap).
It is sized so that it can be inserted by hand. In a certain optical housing 33, as shown in FIG.
6 and a pair of mounting screw holes 37 are provided, and in another optical housing 33a as shown in FIG.
0 is set.

In the case of FIG. 2, the positioning hole 31 of the light source unit 20 and the positioning protrusion 36 of the optical housing 33 are fitted to determine the laser emission position of the light source unit 20, and the holder is positioned in the optical axis direction. 27 vertical part 27b
After positioning the front surface of the side wall 34 by bringing it into contact with the outer surface of the side wall 34,
The light source unit 20 is fixed to the side wall 34 by screwing the mounting screw 41 into the mounting screw hole 37 through the mounting hole 32 .

In the case of FIG. 3, the positioning hole 29 of the light source unit 20 and the positioning protrusion 39 of the optical housing 33 are fitted to determine the laser emission position and the optical axis direction of the light source unit 20, and the mounting hole is 30 into the mounting screw hole 40, and attach the light source unit 20.
is fixed on the bottom 38.

In this way, the holder 2 of the light source unit 20
If the positioning hole and the mounting hole are provided in the optical housing 33 symmetrically with respect to the laser optical axis, and in the same manner in the horizontal part 27a and the vertical part 27b, regardless of the shape of the positioning part of the optical housing 33, The light source unit 20 can be attached vertically and horizontally.

Note that fixing of the light source unit 20 is not limited to screwing, but may also be fixed by caulking as shown in FIG. 4 or by snap-hitting as shown in FIG. 5. In addition, the holder 27 has a positioning protrusion,
A positioning hole may be provided in the optical housing 33.

Next, FIG. 6 shows an embodiment in which the present invention is applied to the imaging lens 23. Plastic imaging lens 2
At the reference plane 23a of No. 3, at its center, that is, at the intersection of the lens center line and the object side (incident side) principal point, as shown in FIG.
A positioning projection (pin) 43 is integrally provided. On the other hand, a positioning hole 45 is provided in the reference surface 44 of the optical housing, and a pair of rotation regulating protrusions 46 are provided on both left and right sides of the positioning hole 45 .

In the case of FIG. 6, the imaging lens 23 is positioned and fixed on the optical housing 33 as follows. The positioning protrusion 43 of the imaging lens 23 is fitted into the positioning hole 45, and the reference surface 23a of the imaging lens 23 is joined to the reference surface 44 of the optical housing 33 by adhesive or the like. Further, both ends 23b of the imaging lens 23 are engaged with the rotation regulating protrusion 46 to regulate rotation of the imaging lens 23 about the positioning protrusion 43.

FIG. 8 shows another embodiment of the present invention applied to the imaging lens 23. In FIG. In this case, the imaging lens 23 is constructed by combining two plastic lenses 47 and 48 on a common plate-shaped lens holding member 49. The material of this lens holding member 49 is plastic lenses 47 and 48.
The plastic lenses 47 and 48 expand and contract in the same way as the plastic lenses 47 and 48 expand and contract due to temperature changes. Projecting walls 50 provided on both sides of the upper surface of the lens holding member 49
, a recess 51 into which both ends 47a of the plastic lens 47 are fitted, and a recess 51 into which both ends 47a of the plastic lens 48 are fitted.
A recess 52 is formed into which the recess 8a is fitted. The plastic lenses 47 and 48 are positioned by fitting their ends 47a and 48a into the recesses 51 and 52, and are fixed onto the lens holding member 49 by adhesive or the like. Further, a positioning projection (pin) 53 is integrally provided at the center of the lower surface of the lens holding member 49. As shown in FIG. 9, the position of this positioning protrusion 53 is at the intersection of the lens center line O and the object side (incident side) principal point P1 of the lens group. Note that P2 is the image-side principal point.

In the case of FIG. 8, the imaging lens 23 is positioned and fixed on the optical housing via the lens holding member 49 as follows. That is, the positioning protrusion 53 of the lens holding member 49 is fitted into the positioning hole 54 of the optical housing 33, and the mounting screw 56 is inserted into the optical housing 33 through the long hole 55 provided at both ends of the lens holding member 49 via the washer 57. screw into the screw hole 58 of the imaging lens 23.
to be fixed.

In either case of FIGS. 6 and 8, the imaging lens 23 has a positioning protrusion 43 or 53 on the lens center line.
Since it is fixed on the optical housing 33 using the fulcrum, it can freely expand and contract from the center in the longitudinal direction to both ends, and the optical axis is maintained constant even when the temperature changes. Moreover, by providing the positioning protrusions 43 and 53 at the intersections as described above, it is possible to expect an improvement in optical characteristics.

[0026]

According to claim 1 of the present invention, the light source unit can be positioned and fixed in common and with high precision regardless of the shape of the light source unit mounting portion of the optical housing, and the cost for positioning adjustment can be reduced.

According to the second aspect, when the lens barrel of the light source unit is inserted through the side wall of the optical housing, there is no need to change the shape of the optical housing depending on the size of the outer diameter of the lens barrel.

According to claim 3, since the imaging lens is fixed on the optical housing using the positioning protrusion on the center line of the lens as a fulcrum, the lens can freely expand and contract from the center in the longitudinal direction to both ends. Since the optical axis remains constant even when the temperature changes, stress due to temperature changes does not occur, and it can always be kept stable.

According to claim 4, even if the positioning protrusion cannot be provided integrally with the lens, the same effect as in claim 3 can be obtained. Further, since the lens group can be handled as one unit, it is advantageous in terms of the assembly process, and replacement is also facilitated.

According to claim 5, by providing the positioning protrusion at the intersection of the lens center line and the object-side principal point, the principal point can always be placed on the optical axis, which improves optical characteristics more than before. This is advantageous against eccentricity.

According to claim 6, there is an effect that combines the above-mentioned claims 1 and 3.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an optical scanning device according to the present invention.

FIG. 2 is a perspective view of an embodiment in which the present invention is applied to a light source unit.

FIG. 3 is a perspective view of the same as above when the light source unit is attached to another optical unit.

FIG. 4 is a sectional view of a main part of another example of fixing the light source unit to the optical housing.

FIG. 5 is a sectional view of a main part of another example of fixing the light source unit to the optical housing.

FIG. 6 is an exploded perspective view of an embodiment in which the present invention is applied to an imaging lens.

FIG. 7 is a front view of the imaging lens in the same as above.

FIG. 8 is an exploded perspective view of another embodiment in which the present invention is applied to an imaging lens.

FIG. 9 is an explanatory diagram showing positions where positioning protrusions are provided in the example of FIG. 8;

FIG. 10 is a perspective view showing an example of how a conventional light source unit is attached.

FIG. 11 is an explanatory diagram for explaining the shape of an imaging lens.

FIG. 12 is an exploded perspective view of an example of mounting a conventional imaging lens.

[Explanation of symbols]

20 Light source unit 23 Imaging lens 27 Holder 29 Positioning hole 31 Positioning hole 33 Optical housing 35 Notch window part 36 Positioning protrusion 39 Positioning protrusion 43 Positioning protrusion 45 Positioning hole 49 Lens holding member 53 Positioning protrusion 54 Positioning hole

Claims (6)

[Claims] 1. An optical scanning device in which a light source unit in which a light emitting element such as a semiconductor laser and a lens are held in a holder is attached to an optical housing, wherein one of the holder and the optical housing has a plurality of positioning protrusions, and the other has a plurality of positioning protrusions. An optical scanning device characterized in that the light source unit is attached to an optical housing by providing a positioning hole, and fitting the positioning protrusion into the positioning hole. 2. The optical scanning device according to claim 1, wherein the optical housing is provided with a cutout window through which the lens barrel of the light source unit is inserted with a gap formed therein. 3. In an optical scanning device in which light from a light source unit is deflected by a deflector and an image is formed on a scanned surface by an imaging lens mounted on an optical housing, a reference surface for mounting the imaging lens is provided. An optical scanning device characterized in that a positioning protrusion and a positioning hole are provided in the optical housing on the center line thereof, and the imaging lens is mounted on the optical housing by fitting the positioning protrusion and the positioning hole. . 4. The imaging lens is formed by bonding and holding a plurality of lenses on a common holding member, and the positioning protrusion is provided on the center line of the lens group on the holding member. The optical scanning device according to claim 3. 5. The optical scanning device according to claim 3, wherein the positioning protrusion is provided at an intersection between a lens center line and an object-side principal point. 6. An optical scanning device in which a light source unit in which a light emitting element such as a semiconductor laser and a lens are held in a holder, and an imaging lens for forming an image of light deflected by a deflector on a surface to be scanned are attached to an optical housing. A plurality of positioning protrusions are provided on one of the holder and the housing, and a plurality of positioning holes are provided on the other, and the light source unit is attached to the optical housing by fitting the positioning protrusions and the positioning hole, and the light source unit is attached to the optical housing, and the light source unit is attached to the optical housing. A positioning projection is provided on the mounting reference surface of the image lens on the center line thereof, and a positioning hole is provided in the optical housing, and the imaging lens is mounted on the optical housing by fitting the positioning projection and the positioning hole. Features: Optical scanning device.