KR20060013611A - Apparatus and method for molding f-??lens - Google Patents

Abstract

Disclosed is an apparatus and method for forming an F-theta lens, which is capable of improving molding accuracy by forming an effective mirror portion of an F-theta lens at the same pressure in a thermally stable state and increasing the molding speed by a continuous molding process. It is.

The disclosed f-theta lens molding apparatus includes an extruder; A molding die having a molding groove having a predetermined shape through which the liquid resin emitted from the extruder is cooled; A first molding pressure roller for molding the resin into a desired f-theta lens shape for the resin passing through the molding die; A cutter for cutting the molded resin into a predetermined size; It is provided between the first molding pressure roller and the cutter, characterized in that it comprises a; temperature control unit for controlling the ambient temperature of the molded resin.

In addition, the disclosed f-theta lens molding method includes the steps of continuously extruding a high temperature liquid resin; Primarily molding the extruded resin; Remolding the primarily molded resin; Adjusting the ambient temperature of the molded resin such that the difference between the internal temperature of the molded resin and the ambient temperature thereof is minimized; Re-cutting the molded resin to a predetermined size; characterized in that it comprises a.

Description

F-theta lens forming apparatus and method {Apparatus and method for molding f-θlens}

1 is a schematic perspective view showing an optical arrangement of a general laser scanning device.

Figure 2 is a schematic cross-sectional view showing a conventional f-theta lens forming apparatus.

FIG. 3 is a schematic view showing an F-theta lens formed by the molding apparatus of FIG. 2 and a refractive index distribution of each part of the F-theta lens. FIG.

Figure 4 is a schematic cross-sectional view showing a f-theta lens forming apparatus according to an embodiment of the present invention.

5 is a schematic cross-sectional view showing the forming die and the first forming pressure roller of FIG.

Figure 6 is a front view showing a second pressing roller and the temperature control chamber of Figure 4;

Figure 7 is a graph showing the temperature distribution inside the temperature control chamber of Figure 4;

Figure 8a is a schematic diagram showing the refractive index distribution of each part of the F-theta lens molded by the F-theta lens forming apparatus according to an embodiment of the present invention.

Figure 8b is a schematic diagram showing the refractive index distribution of each part of the f-theta lens proposed by the applicant through the Republic of Korea Patent Application 10-2004-0039629.

Explanation of symbols on the main parts of the drawings

30 Extruder 31 Housing                 

33 ... injection 35 ... supply

40 Molding die 41 Molding groove

50 ... 1st pressure forming roller 51 ... 1st forming roller

55 ... 2nd Molding Roller 60 ... 2nd Pressing Roller

61 ... 3rd Molding Roller 65 ... 2nd Molding Roller

70 ... Cutter 80 ... Temperature Control

81 Heater 85 Thermostatic chamber

100 ... F-theta lens

The present invention relates to an F-theta lens forming apparatus and method for forming an F-theta (f-θ) lens having at least one curved surface, and in detail, the effective mirror portion of the F-theta lens is the same in a thermally stable state. The present invention relates to a f-theta lens forming apparatus and method which can be molded by pressure to improve molding precision and improve the molding speed by a continuous molding process.

In general, the F-theta lens is employed in an optical scanning device and the like to focus an incident beam and to correct aberration so as to be formed on an object to be exposed. At least one surface of the F-theta lens, that is, the light incident surface and / or the light exit surface has a curvature shape.

Gwangju president is employed in devices such as laser printers, digital copiers, facsimile, etc., and forms a latent image for the exposed object through the main scanning by the beam deflector and the sub-scanning by the rotation of the exposed object.

Referring to FIG. 1, a conventional optical scanning device includes a light source 1 for generating and irradiating a beam, and a beam piece for deflecting an incident beam such that the beam emitted from the light source 1 is main scanned on the exposed object 15. The fragrance 7 and the F-theta lens 11 which correct | amend the optical aberration contained in the beam deflected by this beam deflector 7 are included. Further, on the optical path between the light source 1 and the beam deflector 7, a collimating lens 3 for focusing the diverging beam irradiated from the light source 1 to be parallel light, and a cylindrical lens for shaping the parallel light. (5) is further provided.

As the F-theta lens 11, two to three glass-finished lenses have been used, but in recent years, it has been replaced by one plastic material in accordance with the trend of low cost.

In the case of a plastic material, the high temperature liquid plastic resin is press-filled into a mold through a molding apparatus having a structure as shown in FIG. 2 and then cooled and molded.

Referring to FIG. 2, a conventional cylinder lens forming apparatus includes an extruder 21 for injecting a high temperature liquid resin and a mold for molding an F-theta lens 12 by receiving a resin discharged from the extruder 21 ( 25).

The mold 25 is composed of two parts, one or a plurality of molding spaces 26 having a shape corresponding to the F-theta lens 12 to be molded therein, and the extruder 21 It has an injection path 27 to inject the injected resin into the molding space (26). Therefore, the resin 23 injected into the molding space 26 through the injection path 27 is cooled while maintaining the external shape corresponding to the shape of the molding space 26, and the F-theta lens 11 ′ is cooled. do. The F-theta lens 12 formed as described above is cut by a portion corresponding to the injection path 27, so that the F-theta lens 11 ′ having the gate 12a as shown in FIG. 3 is formed. do. The gate 12a protrudes from the side wall of the F-theta lens 11 and corresponds to a boundary portion between the injection path 27 and the molding space 26.

On the other hand, the f-theta lens 12 configured as described above has a problem in that the pressure difference and the radius of curvature are generated by injecting the resin 23 from the side on which the gate 12a is formed to the opposite side. have.

FIG. 3 is a schematic diagram illustrating an F-theta lens molded by the molding apparatus of FIG. 2 and a refractive index distribution of each part of the F-theta lens. Referring to FIG. 3, since resin is injected from the gate 12a side to the opposite side through the injection path, a pressure difference occurs in the longitudinal direction (x-axis direction). That is, it can be seen that the pressure on the side of the gate 12a is high and the pressure gradually decreases toward the opposite side. Due to this difference in injection pressure, a deviation of ΔX occurs between the center of the refractive index and the center of the F-theta lens. That is, after molding is completed, the difference between the internal refractive index on the side of the gate 12a and the other side becomes large.

Therefore, the refractive index gradient on the opposite side of the gate 12a becomes larger than the gate 12a side, and the focal length on the opposite side of the gate 12a becomes longer than on the gate 12a side, resulting in the performance of the optical scanning device. There is a problem that is adversely affected. In addition, by manufacturing the f-theta lens 12 discontinuously, there is a disadvantage that the productivity is low.

The present invention has been made in view of the above problems, and the molding of the effective mirror portion of the F-theta lens at the same pressure in a thermally stable state to improve the molding precision and to improve the molding speed in a continuous molding process It is an object of the present invention to provide a f-theta lens forming apparatus and method which can be improved.

In order to achieve the above object, the present invention is an F-theta lens forming apparatus for molding an F-theta lens having at least one surface, the extruder for continuously extruding a high temperature liquid resin; A molding die having a molding groove having a predetermined shape through which the liquid resin emitted from the extruder is cooled; A first molding pressing roller rotatably mounted and rotatable with respect to the molding die to pressurize while varying the height according to the passing position of the resin passing through the molding die to mold the resin into a desired f-theta lens shape; A cutter for cutting the molded resin into a predetermined size; It is provided between the first molding pressure roller and the cutter, the temperature control unit for controlling the ambient temperature of the molded resin; including, characterized in that the temperature difference between the inside of the resin and the resin can be minimized.

In addition, an F-theta lens molding method for forming an F-theta lens having at least one curved surface according to the present invention for achieving the above object comprises the steps of: continuously extruding a high temperature liquid resin; Preparing a first press-molding roller arranged to be moved up and down, and forming the first press while changing the height according to the passing position of the extruded resin; Preparing a second press-molding roller arranged to be elevated and remolding the first molded resin; Adjusting the ambient temperature of the molded resin such that the difference between the internal temperature of the molded resin and the ambient temperature thereof is minimized; Re-cutting the molded resin to a predetermined size; characterized in that it is possible to continuously mold a plurality of F-theta lens.

Hereinafter, an F-theta lens forming apparatus and method according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 4, the F-theta lens molding apparatus according to the exemplary embodiment of the present invention includes an extruder 30, a molding die 40 and a first molding pressure roller 50 which are primarily molded, and a cutter 70. And a temperature controller 80.

The extruder 30 continuously extrudes a high temperature liquid resin 37, a housing 31, an injection part 33 for injecting a liquid resin into the housing 31, and an interior of the housing 31. And a supply unit 35 rotatably installed at the ejecting resin injected into the molding die 40.

The molding die 40 includes a molding groove 41 having a predetermined shape through which the liquid resin 37 emitted from the extruder 30 is cooled while passing. Referring to FIG. 5, the forming groove 41 has a width corresponding to the outer shape of the F-theta lens to be molded, in particular, the width between the parallel, and is formed through the inside of the forming die 40. Therefore, the resin injected through one end of the molding groove 41 is cooled while being directed to the other end while maintaining the shape corresponding to the molding groove 41 and is primarily in the shape corresponding to the F-theta lens 100. Is molded into.

The first molding pressure roller 50 is installed to be elevated and rotatable with respect to the molding die 40. The first forming pressure roller 50 is pressed while varying the height depending on the passing position of the resin 37 passing through the forming groove 41, thereby forming a portion corresponding to the curved portion.

Referring to FIG. 5, the first forming pressure roller 50 includes first and second forming rollers 51 and 55. The first forming roller 51 is rotatably installed, and a first retracting groove 51a corresponding to the first curved surface 101 of the F-theta lens 100 is formed on the outer circumferential surface thereof. The second molding roller 55 is rotatably installed in a state in which the second molding roller 55 is spaced apart from the first molding roller 51, and a second curved surface 103 of the F-theta lens 100 is formed on an outer circumferential surface thereof. The second inlet groove 55a corresponding to) is formed. Here, the first and / or second molding rollers 51 and 55 are installed on the molding die 40 so as to be able to move up and down in the direction of the arrow, and are rotated about the rotation axis when the molding is performed and ascend and move therein. The resin 37 injected into the space is molded into a shape corresponding to the curvature of the F-theta lens 100 to be molded.

The first and / or second forming rollers 51 and 55 may have curved surfaces of the first and second inlet grooves 51a and 55a to satisfy a function represented by Equations 1 and 2 below. And lift and exercise. That is, the f-theta lens 100 is designed such that the curvature r in the vertical direction and the thickness z ₀ vary depending on the length y when the length direction is y, and has a function form as shown in Equation (1).

In addition, when the first and second forming rollers 51 and 55 are processed, the radius of curvature r becomes a function of the radial angle θ, and satisfies the relationship of equation (2).

Therefore, the first and second forming rollers 51 and 55 are machined to have a radius of curvature r different according to the radial angle θ according to their angles based on Equations 1 and 2 above. The desired F-theta lens 100 can be formed by elevating the first and second forming rollers 51 and 55 processed as described above according to z ₀ .

Here, the lifting motion of the first and / or second forming rollers 51 and 55 may be implemented by a cam driving mechanism or the like, and since the configuration itself is widely known, a detailed description thereof will be omitted.

The solidified resin continuously extruded from the molding die 40 has an F-theta lens shape and shrinks as the temperature decreases.

At this time, in order to increase the molding precision of the F-theta lens, the present invention preferably further comprises a second forming pressure roller 60 between the forming die 40 and the cutter (60). The second molding press roller 60 presses the resin formed by the first molding press roller 50 and molds again.

4 and 6, the second forming pressure rollers 60 are disposed to face each other, and include third and fourth forming rollers 61 and 65 rotatably installed, respectively.

On the outer circumferential surface of each of the third and fourth forming rollers 61 and 65, third and fourth retracting grooves corresponding to each of the first and second curved surfaces 101 and 103 of the F-theta lens 100 are formed. 61a) 65a are formed, respectively. The first and / or second forming rollers 61 and 65 are installed to be elevated in the direction of the arrow, and are rotated about the rotational axis at the time of performing the molding and are simultaneously elevated to form the molding die 40 and the first molding. The resin 37 primarily molded by the pressure roller 50 is again molded. In this way, by further molding the second molding press roller 60, the processing accuracy can be increased.

In particular, when the surface temperature of the second forming pressure roller 60 is set to a near value as the glass transition temperature, the transferability of the molded lens can be improved.

Here, the lifting motion of the third and / or fourth forming rollers 61 and 65 may be implemented by a cam driving mechanism or the like, similarly to the first and / or second forming rollers 51 and 55. The description will be omitted. Further, the shape and the lifting motion of the third and fourth inlet grooves 61a and 65a are set in the manner as described based on the equations (1) and (2).                     

The cutter 70 cuts the resin 37 'having been molded to a predetermined size while passing through the second molding pressure roller 60. Therefore, when the F-theta lens 100 is molded by using the above-described molding apparatus, the plurality of F-theta lenses 100 may be continuously completed.

As described above, in the case of forming the F-theta lens 100 through the molding process, the resin 37 ′ having the molding is cooled to have a refractive index distribution inside the lens that is proportional to the internal residual stress. Here, the residual stress is proportional to the temperature difference between the resin internal temperature and the resin surroundings.

On the other hand, when the molded resin is exposed to an external temperature at room temperature as soon as it passes through the second molding pressure roller 60, the residual stress increases according to the temperature difference between the inside and the outside of the resin, thereby increasing the internal refractive index distribution. . The temperature adjusting part 80 is provided between the first press-molding roller 50 and the cutter 70 to solve this problem, and the molding resin in a state where the temperature difference between the inside of the resin and the resin is minimized. The ambient temperature of the molded resin is controlled to cool. In this way, when controlling the ambient temperature, the resin can be cooled slowly, so that the residual stress can be relaxed.

To this end, as shown in FIG. 6, the temperature adjusting part 80 is provided on at least one side of the second molding pressure roller 60 and a heater 81 for heating the periphery thereof, and the heater 81. And a thermostatic chamber 85 for receiving.

Here, the temperature control unit 80, as shown in Figure 7, it is preferable to set the temperature (T _c ) inside the temperature control chamber (85). That is, the internal temperature T _{c of the} chamber becomes the glass transition temperature T _g at the portion close to the molding die 40, and gradually decreases in temperature relative to the molding resin traveling direction, and the surrounding area around the cutter 70. It is preferable that the air temperature T _air be set. Such a temperature distribution can be set according to the arrangement of the temperature control chamber 85 and the degree of control of the heater 81. In addition, in installing the heater 81 inside the temperature control chamber 85, by forming the heater 81 on the side surface (surface that does not function as a lens) of the molded resin 37 ', molding of the optical surface that functions as a lens is performed. You can make it go smoothly.

Hereinafter, a molding method using the molding apparatus will be described. Referring to FIG. 4, the molding method according to the present embodiment includes the extrusion step, the primary molding step, the molding step again, the step of adjusting the ambient temperature of the molded resin, and the size of the molded resin for each F-theta lens. Cutting into a furnace. The extruding step continuously extrudes the hot liquid resin 37 toward the molding die 40 through the extruder 30.

The primary molding step is the f-theta lens by rotating and elevating the first pressure forming roller 50 including the first and second forming rollers 51 and 55 while passing the extruded resin through the forming groove 41. It consists of a process of primary molding into a shape corresponding to the and a process of cooling.

Again, the molding step is performed by the second press forming roller 60 including the third and fourth forming rollers 61 and 65 spaced apart by a predetermined interval. That is, the space provided between the third and fourth forming rollers 61 and 65 has a shape corresponding to the F-theta lens 100 after processing, and the resin 37 'is again caused by the pressing force in this space. Molded.

The step of adjusting the ambient temperature of the molded resin again controls the heater (81 in FIG. 7) so that the internal temperature of the molded resin and the ambient temperature difference thereof are minimized and cooled.

 Subsequently, the F-theta lens 100 may be continuously formed by cutting to a size suitable for the F-theta lens 100 through a cutting step.

The F-theta lens 100 completed as described above does not have a gate (12a in FIG. 3) unlike the conventional F-theta lens due to differences in its molding process. In addition, by molding the F-theta lens 100 in a manner of transferring the resin, the pressure in the longitudinal direction of each F-theta lens 100 can be kept constant.

Here, FIG. 8A is a schematic diagram illustrating a refractive index distribution of each part of the F-theta lens 100 formed by the F-theta lens molding apparatus according to the embodiment of the present invention. FIG. 8B is a schematic diagram showing the refractive index distribution of each part of the F-theta lens 90 formed by the F-theta lens molding apparatus proposed by the applicant through Korean Patent Application No. 10-2004-0039629.

Referring to FIG. 8A, since the F-theta lens 100 is molded in the conveying direction, the extrusion pressure is constant in the longitudinal direction (x-axis direction) in the same direction as the conveying direction. Therefore, the refractive index distribution of the F-theta lens 100 is also symmetrical with respect to the center thereof. In this respect, it is substantially the same as the F-theta lens 90 shown in Fig. 8B. 8A and 8B, the refractive index distribution of the F-theta lens 100 of the F-theta lens 100 according to the present invention is formed by the molding apparatus shown in 8B. It can be seen that compared to the large relief.

Since the f-theta lens molding apparatus and method according to the present invention configured as described above performs the molding process continuously, the molding time of each f-theta lens can be significantly shortened compared to the non-continuous molding apparatus, thereby improving productivity. You can. By controlling the cooling rate by adjusting the temperature of the section between the cutters in the pressure forming roller, the optical performance of the F-theta lens can be greatly improved by reducing residual stress, internal refractive index unevenness, and poor molding caused by rapid cooling. have.

The above embodiments are merely exemplary, and various modifications and equivalent other embodiments are possible from those skilled in the art. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the invention described in the claims below.

Claims (4)

An F-theta lens molding apparatus for molding an F-theta lens having at least one curved surface, An extruder for continuously extruding hot liquid resin; A molding die having a molding groove having a predetermined shape through which the liquid resin emitted from the extruder is cooled; A first molding pressing roller rotatably mounted and rotatable with respect to the molding die to pressurize while varying the height according to the passing position of the resin passing through the molding die to mold the resin into a desired f-theta lens shape; A cutter for cutting the molded resin into a predetermined size; It is provided between the first molding pressure roller and the cutter, the temperature control unit for controlling the ambient temperature of the molded resin; including, F characterized in that to minimize the temperature difference between the inside of the resin and the resin -Theta lens forming apparatus. The method of claim 1, And a second molding press roller disposed between the molding die and the cutter to press the resin molded by the first molding press roller and to mold again. The method of claim 2, The temperature control unit, A heater provided on at least one side of the second forming pressure roller to heat the periphery of the second forming pressure roller; And a temperature control chamber for receiving the heater. In the F-theta lens molding method of molding the F-theta lens having at least one surface curved, Continuously extruding the high temperature liquid resin; Preparing a first press-molding roller arranged to be moved up and down, and forming the first press while changing the height according to the passing position of the extruded resin; Preparing a second press-molding roller arranged to be elevated and remolding the first molded resin; Adjusting the ambient temperature of the molded resin such that the difference between the internal temperature of the molded resin and the ambient temperature thereof is minimized; And cutting the molded resin to a predetermined size. The f-theta lens molding method of claim 1, wherein the plurality of F-theta lenses are continuously formed.

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