JP3387827B2 - Scanning optical system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical system used in a laser printer or the like.

[0002]

2. Description of the Related Art Conventionally, in a scanning optical system of this type, a collimator lens 2, a glass cylinder lens 3, and a polygon mirror 4 are sequentially arranged in the emitting direction of laser light emitted from a laser light source 1 as shown in FIG. And the lenses 5a and 5a are arranged in the deflection direction of the polygon mirror 4.
An fθ lens 5 composed of b is arranged. The laser light is converted into a substantially parallel light by the collimator lens 2, and then the light is condensed by the glass cylinder lens 3,
A focal line is connected to the reflecting surface of the polygon mirror 4. Due to the deflecting action of the polygon mirror 4 and the converging action of the fθ lens 5, the laser beam scans in the main scanning cross section while forming a laser spot on the image plane (not shown).

The glass cylinder lens 3 is finely adjusted in the X-axis direction when assembling and adjusting the scanning optical system so that the spot on the image plane satisfies the desired performance. FIG. 10 is a schematic view for adjusting the glass cylinder lens 3. The glass cylinder lens 3 contacts the guide surface 12 and the side surface portion 13 provided on the casing 11, and adjusts the position in the X-axis direction as necessary. it can.

The glass cylinder lens 3 has an optical effective area 14 with respect to the optical axis O, and the seating surface 15 thereof is processed so that the parallelism with the generatrix of the glass cylinder lens 3 is as accurate as the polishing level. On the other hand, the casing 11 is molded by resin, and includes the guide surface 12, the side surface portion 13, and the adhesive surface 1.
6 is formed. By contacting the glass cylinder lens 3 with the guide surface 12, it is possible to eliminate the difficulty of achieving flatness in a wide range of the resin member by molding, and to arrange the glass cylinder lens 3 with high accuracy. it can.

Further, in order to reduce the occurrence of burrs due to molding and improve the accuracy of the guide surface 12, it is desirable that the gap between the guide surface 12 and the adhesive surface 16 be 0.2 mm or more.

Glass cylinder lens 3 and casing 11
For fixing, the adhesive is generally flowed into the gap between the adhesive surface 16 and the lens seat surface 15 and fixed. Also,
In order to omit the step of flowing the adhesive, the adhesive surface 1
6 or a method of applying an adhesive to the lens seat surface 15 is known. Furthermore, in order to shorten the fixing time of the adhesive, a method of heating, a method of using a UV adhesive, etc. have been realized.

Normally, the glass cylinder lens 3 is a single lens, but depending on the specifications, a glass cylinder lens group 23 composed of a plurality of glass cylinder lenses 21 and 22 may be used as shown in FIG. In this case, the ends 21a, 22a and the ends 21b, 22b of the respective lenses are designed so as to be in contact with each other at the ends (marginal contact), and the lenses can be used as a cemented lens, and adjustment is facilitated.

[0008]

However, when the glass cylinder lens 3 is replaced with a synthetic resin mold lens for the purpose of cost reduction, the following problems have become apparent.

(1) It is difficult to adjust the seating surface accuracy of the cylinder lens. Although the seating surface 15 of the glass cylinder lens 3 achieves accuracy by polishing, the synthetic resin molded lens cannot achieve the accuracy of flatness in a wide area like the seating surface 15 because of molding by the mold. As a result, the accuracy around the optical axis of the cylinder lens 3 is not achieved, and the imaging performance of the laser spot deteriorates.

(2) Sliding property of cylinder lens adjustment is deteriorated. Synthetic resin casing 11 and glass cylinder lens 3
Compared with the frictional force with the casing 11 between synthetic resin materials
In the case of a cylinder lens, the frictional force is very large, and the slidability deteriorates. In particular, if the seating surface 15 of the cylinder lens 3 is brought into contact with the three-point projection as a countermeasure of (1), the catching portion with the casing 11 increases and the slidability is further deteriorated. This deterioration of the slidability causes a decrease in workability during assembly and adjustment, which increases the number of work steps and leads to an increase in cost.

(3) The lens surface accuracy is deteriorated by the sink mark of the adhesive material at the time of bonding. Adhesive surface 1 between the seat surface 15 of the cylinder lens and the casing 11
When the adhesive solidifies in the gap of 6, the sink of the adhesive occurs.

Generally, the rigidity is higher in the order of the glass lens, the casing (PC material containing glass, etc.) and the synthetic resin lens (PC, etc.), so that the synthetic resin cylinder lens is pulled by the sink mark and the surface accuracy of the lens surface is lowered. , The imaging performance of the laser spot deteriorates. When the rail surface is coated with an adhesive, sink marks are reduced, but the adhesive layer has a variation of 5 to 20 μm, and the problem (1) occurs.

(4) Heat is generated during bonding, and distortion occurs after cooling. The synthetic resin cylinder lens and the casing 11 are heated to a high temperature when heat is applied at the time of bonding or UV bonding, which generates a large amount of heat. Especially when a large amount of adhesive material is used to obtain a desired adhesive force, or in order to shorten the fixing time, the amount of heat applied or UV
Increasing the irradiation dose increases the temperature rise. In addition, FIG.
In the cylinder lens group in which a plurality of lenses are bonded as shown in (1), since the bonding surface is wide, the heat dissipation is poor and the temperature rise is large. If this temperature rise is large, the synthetic resin cylinder lens and the casing 11 are melted, or due to the difference in linear expansion between the casing 11 and the synthetic resin cylinder lens, distortion occurs when cooling after fixing at high temperature, and the surface accuracy of the lens is reduced. This lowers the image forming performance of the laser spot.

The object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a scanning optical system which has good workability and can be adjusted with high accuracy when fixing a cylinder lens.

[0015]

A scanning optical system according to the present invention for achieving the above object comprises a laser light source, a collimator lens, a cylinder lens adjustable in the optical axis direction, a deflector, and an fθ lens. In the scanning optical system having the above, at least two first rail surfaces made of synthetic resin forming a part of the cylinder lens are provided at a contact portion of the cylinder lens that comes into contact with a casing holding the scanning optical system. And a second rail surface is provided at a contact portion of the casing that faces the rail of the cylinder lens.

Further, the scanning optical system according to the present invention is a scanning optical system having a lens made of a synthetic resin which can be adjusted in the optical axis direction with respect to a casing, and the lens is provided at a contact portion of the lens which comes into contact with the casing. At least two first rail surfaces that form a part of the first rail surface are formed, and a second rail surface is provided at a contact portion of the casing that faces the first rail surface.

Further, the scanning optical system according to the present invention is a scanning optical system in which a hybrid lens composed of a plurality of lenses is fixed to a casing with an adhesive, and a lens forming a part of the hybrid lens and A first gap extending substantially in the optical axis direction is provided between the casings, and a second gap extending substantially perpendicular to the generatrix direction of the lens is provided in the vicinity of the joint portion of the lenses forming the hybrid lens. The gap is communicated with the second gap to allow air to flow.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a block diagram of the scanning optical system of the first embodiment, which is a hybrid composed of a collimator lens 32, a first cylinder lens 33 and a second cylinder lens 34 in the emitting direction of laser light from a laser light source 31. The cylinder lens 35 and the polygon mirror 36 are sequentially arranged. An fθ lens 37 including lenses 37a and 37b is arranged in the deflection direction of the polygon mirror 36, and a plane that is perpendicular to the rotation axis of the polygon mirror 36 and includes the optical axis is defined as a main scanning cross section. When the surface including the is a sub-scanning cross section, the laser light emitted from the laser light source 31 is converted into substantially parallel light by the collimator lens 32, and then the hybrid cylinder lens 35 is used.
As a result, the laser light that has been subjected to the light condensing action in the sub-scanning section forms a focal line on the reflecting surface of the polygon mirror 36.

FIG. 2 is a side view of the contact surface between the hybrid cylinder lens 35 and the casing 41, and FIG. 3 is a sectional view. The casing 41 is a PC containing 20% glass for arranging and holding the scanning optical system shown in FIG. The casing 41 is formed with at least two rail surfaces 42, a convex flat surface portion 43, and one side surface portion 44.

The hybrid cylinder lens 35 is formed by cementing the first cylinder lens 33 and the second cylinder lens 34 as described above, and the first cylinder lens 33 is formed.
Is a polished glass and is produced by an ordinary lens processing process. In addition, the second cylinder lens 3
4 is a synthetic resin (low hygroscopic acrylic: Acrypet WF-100 manufactured by Mitsubishi Rayon) which is molded. The first and second cylinder lenses 33 and 34 are joined so that the generatrix of the cylindrical surface coincides with the optical axis O,
An optical effective area 45 exists with respect to the optical axis O. Outside the optical effective area 45 of the second cylinder lens 34, two flange portions 46 for holding at the time of assembly and at least two rail seat surfaces 47 for sliding with respect to the rail surface 42 of the casing 41.
Has been added. The rail seat surface 47 has a long shape in the X-axis direction, and slidability is improved by providing chamfered portions 48 at the front and rear ends in the X-axis direction. Furthermore, the second
A side surface seat 49 is formed on a side portion of the cylindrical lens in contact with the side surface portion 44 of the casing 41.

FIG. 4 is a perspective view of the hybrid cylinder lens 35, in which the cylindrical surface 51 of the second cylinder lens 34 projects inward at the end portion in the sub-scanning direction.
One lens receiving portion 52 and two lens receiving portions 53 are provided, and a side wall portion 54 extends from the cylindrical surface 51 toward the first cylinder lens 33. The bottom portion of the side wall portion 54 serves as a rail seat surface 47, one side surface of the side wall portion 54 serves as a side surface seat 49, and a flange portion 46 is provided on a side portion of the side wall portion 54. In the first and second cylinder lenses 33 and 34, the generatrices of their cylindrical surfaces are the optical axis O.
It is positioned by a jig so that it almost coincides with. Further, as a joining method, a UV adhesive can be applied to the lens receiving portions 52 and 53 and fixed by UV irradiation. Or
The size of the first cylinder lens 33 in the Y-axis direction and the gap between the inner walls of the side wall portions 54 of the second cylinder lens 34 are substantially matched, and an adhesive is applied to the side wall portions 54 of the first cylinder lens 35. Good.

The lens receiving portion 52 and the lens receiving portion 53 are arranged at positions asymmetrical to each other in the Z direction. Therefore, since the lower surface 55 of the lens receiving portion 52 is joined to the casing 41, the Y
It can be provided near the central portion in the axial direction. Also,
In order to stably fix the first cylinder lens 35,
The lens receiving portion 53 is separated from the lens receiving portion 52 in the Z-axis direction,
Moreover, it is preferable to install them at positions apart from each other in the Y-axis direction.

On the other hand, by projecting the lens receiving portions 52 and 53 inward, the arrow ← ---- for suppressing the temperature rise when the hybrid cylinder lens 35 is bonded to the casing 41 by using the UV adhesive. It is possible to secure the airways of the heat. Moreover, the effect is further improved by forcibly cooling using an air flow or an air suction device. If the entire area of the end of the cylindrical surface 51 is bonded, such an airway cannot be secured.

The hybrid cylinder lens 35 and the casing 41 are respectively provided with a rail surface 42 and a rail seat surface 47.
And the side surface portion 44 and the side surface seat 49 are in contact with each other. The rail surface 42 and the rail seat surface 47 are projected from the surroundings, and by adopting a sliding type in a limited range, a highly accurate flatness is achieved. The width of the rail surface 42 in the Y direction is preferably 1/5 or less of the width of the lens surface or 5 mm or less, whichever is smaller. Since the flatness of the surface by the sliding type is about 0.2 to 0.5% of the length, the parallelism of the generatrix of the lens is 0.
002 or less is achieved. On the other hand, if the width of the rail exceeds 5 mm, the frictional resistance at the time of cylinder adjustment is increased, and the workability at the time of assembly adjustment is deteriorated.

Further, in order to reduce the occurrence of burrs due to molding and improve the accuracy of the rail surface 42, it is desirable that the projection amount D1 of the rail surface 42 in FIG. 3 be 0.2 mm or more. The convex plane portion 43 is about 0.
It is designed to be 15 mm higher, and the gap D2 between the convex flat surface portion 43 and the bottom surface of the second cylinder lens 34 is 0.05 mm.

The hybrid cylinder lens 35 is arranged so as to come into contact with the side surface portion 44 and the side surface seat 49, and is adjusted in the X-axis direction so that the imaging performance on the image plane becomes desired. This adjustment is called cylinder adjustment, and a known automatic adjustment such as fine adjustment of the hybrid cylinder lens 35 by a pulse motor or the like can be used by providing a CCD camera at the image formation position and numerically processing the image formation state. .

The hybrid cylinder lens 35 and the casing 41 are fixed by injecting an adhesive into the gap between the convex flat surface portion 43 and the bottom surface 56 of the second cylinder lens 34 and fixing them. If the adhesive is excessively applied, the adhesive is collected in these spaces 57, so that the adhesive can be prevented from flowing into between the rail surface 42 and the rail seat surface 47. Further, in order to save the trouble of flowing the adhesive, it is preferable to apply an appropriate amount of the adhesive on the convex flat surface portion 43 in advance. Also, in order to reduce the fixing time of the adhesive, a UV adhesive (UVZ-made by Sumitomo 3M
It is more preferable to use M300L, etc.).

The convex flat portion 43 and the second cylinder lens 34
The clearance D2 is preferably 0.02 mm or more in consideration of variations in flatness during molding. Below this, when the flatness varies, the convex flat surface portion 43 and the second cylinder lens 34 come into contact with each other, and the rail surface 42 and the rail seat surface 47 do not come into contact, and the accuracy of the posture of the hybrid cylinder lens 35 cannot be achieved. . Further, as described above, since the protrusion amount D1 of the rail surface 42 is required to be 0.2 mm or more for the hybrid cylinder lens 35 and the casing 41, the convex plane portion 43 makes the gap D2 0.4 m.
If it is m or less, the amount of the adhesive can be reduced as compared with the conventional example.

FIG. 5 shows a second embodiment, and the same symbols as those in FIG. 4 indicate the same members. In the second embodiment, at the end of the cylindrical surface 51 of the second cylinder lens 34 in the sub-scanning direction, one lens receiving portion 52 and two lens receiving portions 53 (one (Only shown), and is provided in the opposite direction to that of FIG. In this case also, the function similar to that of the first embodiment is provided, and the arrow ← ----
It is possible to secure an airway for heat as indicated by-.

FIG. 6 shows a third embodiment, and in this case also, the same reference numerals as those in FIG. 4 represent the same members. Two lens receiving portions 58 protruding inward are vertically provided at an end portion of the cylindrical surface 51 of the second cylinder lens 34 in the sub-scanning direction, and a groove 59 is vertically provided inside the side wall portions 54 on both sides. Are formed. Therefore, the arrow of the heat airway ← −
It can be secured along the groove 59 as in-.

FIG. 7 is a sectional view of the fourth embodiment.
The same reference numerals as those used in the above embodiment represent the same members. A concave flat surface portion 63 is provided between the rail surfaces 62 of the casing 61, and a convex flat surface portion 65 is provided between the rail surfaces 64 of the hybrid cylinder lens 35. The gap between the concave flat surface portion 63 and the convex flat surface portion 65 is 0.05 mm.
Designed to be degree.

FIG. 8 shows a sectional view of the fifth embodiment, in which the convex flat portion 72 between the two rails 73 of the casing 71 is Y-shaped.
It is long in the axial direction and is loosely fitted to the rail 43 side. As a result, positioning in the Y-axis direction is performed, and the side surface portion 44 and the side surface seat 49 as shown in FIG. 3 are unnecessary.

[0033]

As described above, in the scanning optical system according to the present invention, the rail seating surface parallel to the optical axis is provided on the lens and the lens seating surface is disposed so as to face the casing. Image performance is improved.

In this case, if chamfering is added to the front and rear of the rail surface of the lens, the slidability during lens adjustment is improved and the workability is improved. Further, when the convex flat surface portion is provided between the rails of the casing, the amount of the adhesive used is reduced, the heat generation amount is reduced, and the distortion of the lens can be suppressed, so that the imaging performance is improved.

The scanning optical system according to the present invention includes the first and
Since the lens is joined to the casing with the second gap provided, the air passage of heat can be secured, the temperature rise at the time of bonding after lens adjustment can be reduced, and the distortion of the lens is suppressed, so that the imaging performance is improved. Further, the cooling time can be shortened, the work man-hours can be reduced, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical system.

FIG. 2 is a side view of the first embodiment.

FIG. 3 is a sectional view.

FIG. 4 is an exploded perspective view.

FIG. 5 is an exploded perspective view of a second embodiment.

FIG. 6 is an exploded perspective view of a third embodiment.

FIG. 7 is a sectional view of a fourth embodiment.

FIG. 8 is a sectional view of a fifth embodiment.

FIG. 9 is a block diagram of an optical system of a conventional example.

FIG. 10 is an explanatory diagram of adjustment of a glass cylinder lens.

FIG. 11 is a configuration diagram of a hybrid cylinder lens.

[Explanation of symbols]

31 laser light source 32 collimator lens 33 First cylinder lens 34 Second cylinder lens 35 Hybrid cylinder lens 36 polygon mirror 37 fθ lens 41, 61, 71 casing 42, 62, 73 Rail surface 43, 65, 72 convex flat surface 44 Side 46 collar part 47, 64 Rail bearing surface 49 side seat 52, 53, 58 Lens receiving part 54 Side wall 59 groove 63 concave flat surface

Claims (11)

(57) [Claims] 1. A laser light source, a collimator lens,
A cylinder lens adjustable in the optical axis direction, a deflector, and f
In a scanning optical system having a θ lens, at least two first rails made of synthetic resin that form a part of the cylinder lens at a contact portion of the cylinder lens that contacts a casing that holds the scanning optical system. Forming a surface,
A scanning optical system, wherein a second rail surface is provided at a contact portion of the casing facing the rail of the cylinder lens. 2. The cylinder lens is a toric lens having different refracting powers in the generatrix direction and the sagittal direction, and the first rail surface parallel to the optical axis direction is provided at least at two positions on the outer peripheral portion. The scanning optical system described. 3. The scanning optical system according to claim 1, wherein the front and rear end surfaces of the first rail surface of the cylinder lens are provided with chamfers or R chamfers. 4. The scanning optical system according to claim 1, wherein a convex surface area is provided in an area between either or both rail surfaces of the casing or the cylinder lens, and the convex surface area serves as an adhesive surface. 5. The scanning optical system according to claim 1, wherein a gap in a region between the casing and at least two first rail surfaces of the cylinder lens is 0.02 to 0.40 mm. 6. The scanning according to claim 1, wherein the cylinder lens is a hybrid cylinder lens composed of a plurality of lenses, and the coupling between the lenses is fixed by contacting at a part of an end portion of the lens in the sub-scanning cross section. Optical system. 7. The scanning optical system according to claim 6, wherein the contact between the ends is asymmetric between the contact position at the end far from the casing and the contact position at the end near the casing. 8. The scanning optical system according to claim 6, wherein the one cylinder lens is made of glass, the other cylinder lens is made of synthetic resin, and the first rail surface is formed on the synthetic resin lens. 9. The casing is adjustable in the optical axis direction.
Scanning optical system with lens made of synthetic resin
The front of the contact part of the lens that contacts the casing.
At least two first rays forming a part of the lens.
Of the case that forms a ruled surface and faces the first rail surface.
Characterized in that a second rail surface is provided at the contact portion of the ring.
Scanning optical system . 10. A hybrid lens composed of a plurality of lenses fixed to a casing with an adhesive.
In the inspection optical system, a part of the hybrid lens is constructed.
Between the lens and the casing
And forming a first gap to configure the hybrid lens.
One that is approximately perpendicular to the generatrix direction of the lens near the lens joint
A second gap extending in the direction is provided, and the first gap and the first gap are provided.
The second gap by communicating that to allow circulation of air
Characteristic scanning optical system . 11. A scanning optical system according to claim 1.
Laser printer having.