JP2009229702A - Method of manufacturing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical element, improving the quantity of transmitted light while maintaining high diffusion of projecting and recessed parts caused by grinding for eliminating uneven luminous intensity distribution. <P>SOLUTION: According to this manufacturing method, a projecting part 16 of the optical element 15 is subjected to grinding so that a roughened surface is formed by a large projecting and recessed part 11 whose form error Pv (Peak to value) is within 10 μm and a small projecting and recessed part whose arithmetic roughness Ra (Reckoning asperity) is 0.29-0.6 μm, which is formed on the surface of the large projecting and recessed part 11. The optical element 15 is held with the projecting part 16 abutted or brought close to a face 21 of a mold bed 22 having the face 21, which is shaped along the projecting part 16 to cover the projecting part 16 only. The mold bed 22 is carried onto a heat plate 24 having a plurality of built-in heat sources 23, thereby heating the mold bed 22. The roughened surface of the projecting part 16 of the optical element 15 is heated by the face 21 of the mold bed 22, thereby melting very small projecting and recessed part 12 of a surface layer of the large projecting and recessed part 11 of the roughened surface of the projecting part 16 so that only the large projecting and recessed part 11 is left undone. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical element capable of improving the amount of transmitted light while maintaining high diffusibility of unevenness caused by grinding for light distribution unevenness.

In recent years, for example, in an illumination optical system such as a backlight of a display device or an endoscope, a small optical element is used for a light source device that irradiates an observation field. In order to diffuse the light emitted from the optical element and eliminate the uneven light distribution of illumination, a technique is known in which fine uneven portions are formed on the optical functional surface of the optical element. (For example, refer to Patent Document 1.)
As a method for forming such irregularities, for example, a method for forming irregularities by grinding is known. (For example, see Patent Document 2.)
6A and 6B are diagrams showing two examples of the shape of the optical element of the light source in the illumination optical system such as an endoscope.

  FIG. 6A shows the lens 4 disposed in the vicinity of the exit 3 for emitting the exit light 2 of the optical fiber 1. The lens 4 has, as an optical function surface, a convex portion 5 that is introduced while scattering the incident light 2 incident from the optical fiber 1, and a planar portion that irradiates the observation field as the irradiated light 6 with the emitted incident light 2 incident while being scattered. 7 two sides.

  FIG. 6B shows the lens 8 disposed in the vicinity of the exit 3 for emitting the exit light 2 of the optical fiber 1. The lens 8 has, as an optical function surface, a convex portion 5 that is introduced while scattering the outgoing light 2 incident from the optical fiber 1, a convex portion 5 that the illumination light 2 enters, and an outgoing light that is incident while being scattered. 3, an internal reflection surface 9 that reflects 2, and a plane portion 10 that irradiates the observation field of view with the reflected scattered light as irradiation light 6.

7 (a) is an enlarged view of the lens 4 shown in FIG. 6 (a), and FIG. 7 (b) is surrounded by a broken-line circle a in FIG. 7 (a) of the convex portion 5 of the lens 4. FIG. It is a figure which expands and shows the part shown by.
The unevenness of the convex portion 5 of the lens 4 shown in FIG. 7 (a) (the same applies to the convex portion 5 of the lens 8 of FIG. 6 (b)), as shown in FIG. It has fine irregularities 12 formed on the surface layer of the large irregularities 11.
JP 2000-193894 A JP 2001-150323 A

  By the way, although the uneven surface ground as described above is easy to obtain light diffusion (there is little unevenness of light distribution), the transmitted light amount of 14 to 15.5 lumen generally required for irradiating the observation field is obtained. It has a problem that it is difficult to secure.

  Generally, in such an optical system, if the roughness of the optical functional surface on which light is incident from the outside is made finer, the amount of light is improved but the diffusibility is deteriorated. Conversely, if the roughness of the unevenness is made rough, the diffusivity is reduced. There is a problem that it is difficult to select among the alternatives of improving the light quantity but deteriorating the light quantity.

  The present invention has been made in view of the above problems, and is an optical element capable of improving the amount of transmitted light while maintaining high diffusibility of unevenness caused by grinding for light distribution unevenness elimination. An object is to provide a manufacturing method.

 In order to achieve the above object, the method for manufacturing an optical element of the present invention heats a rough surface having a function of scattering light among a plurality of functional surfaces of the optical element, and forms a rough surface layer of the rough surface. It is characterized in that fine irregularities are dissolved to form a rough surface consisting only of large irregularities.

  According to the present invention, since the fine unevenness of the surface layer of the rough surface having a large rough surface is dissolved to form a rough surface having large unevenness, the amount of transmitted light can be improved while maintaining the high diffusibility of the unevenness caused by grinding. It is possible to provide a method for manufacturing an optical element capable of achieving the above.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1A is an enlarged view showing the optical element 15 in the first embodiment, and FIG. 7B is a broken line b in FIG. 1A of the convex portion 16 of the optical element 15. It is a figure which expands and shows the part enclosed and shown by.

  In this example, the optical element 15 shown in FIG. 1 (a) is the same as the conventional lens 4 shown in FIGS. 6 (a) and 7 (a) in both use and size. As shown in FIG. 1 (b), the convex portion 16 of FIG. 1B has the fine irregularities 12 on the surface layer of the large irregularities 11 of the rough surface as shown in FIG. It has become a rough surface.

  Here, the large irregularities 11 are irregularities formed with a shape error Pv (Peak to value) within 10 μm, that is, between 0.01 μm and 10 μm. And a small unevenness | corrugation is an unevenness | corrugation currently formed by arithmetic roughness Ra (Reckoning asperity) 0.29-0.6micrometer.

  When this optical element 15 is used in the same manner as the lens 4 shown in FIG. 6 (a), the diffusion effect of incident light due to the large unevenness 11 left undissolved among the unevenness formed by grinding is maintained. Since the fine irregularities 12 on the surface layer disappeared and disappeared, the amount of transmitted light was improved, and it was found that a transmitted amount of light of about 16 to 18 lumens was obtained when measured experimentally.

  FIG. 2 is a diagram showing a basic manufacturing method of the optical element 15 shown in FIGS. 1 (a) and 1 (b). As shown in FIG. 2, the optical element 15 in which the large unevenness 11 immediately after grinding and the fine unevenness 12 on the surface layer are formed on the convex portion 16 has the convex portion 16 on the upper side and the flat portion 17 on the lower side. The flat portion 17 is held by a jig 18.

  A heat plate 20 containing a plurality of heat sources 19 is disposed in the vicinity of the convex portion 16. In this state, the plurality of heat sources 19 are driven to generate heat, the heat plate 20 containing them is heated, the heated heat is radiated to the surface of the optical element 15, and the convex portion 16 of the optical element 15 is heated. Is done.

The rough surface of the convex portion 16 dissolves the fine unevenness 12 (see FIG. 7 (b)) on the surface layer of the unevenness 11 having a large rough surface by the above heating, and is shown in FIGS. 1 (a) and 1 (b). As shown in FIG.
(Second Embodiment)
In the meantime, in the method for correcting the rough surface shown in FIG. 2, the distance from the heat plate 20 is different between the central portion and the peripheral portion of the convex portion 16, and the central portion is closer to the heat plate 20 than the peripheral portion. Therefore, the central portion is first corrected to a rough surface composed of the large irregularities 11, so that the light transmittance is different between the central portion and the peripheral portion.

  Even in this case, the transmittance is improved while maintaining the diffusibility of the incident light as compared with the conventional case, but there is a method for correcting the rough surface which further improves the transmittance while maintaining the diffusibility. This will be described below as a second embodiment.

  FIG. 3 is a diagram for explaining a method for correcting a rough surface of the optical element 15 in the second embodiment. In the rough surface correcting method of this example, as shown in FIG. 3, first, a mold having a surface 21 having a shape that covers only the rough surface of the convex portion 16 in a shape along the shape of the rough surface of the convex portion 16. A stand 22 is provided.

  Next, the optical element 15 is held on the mold table 22 by a holding member (not shown) by bringing the rough surface of the convex portion 16 of the optical element 15 into contact with or close to the surface 21 of the mold table 22. When the rough surface of the convex portion 16 of the optical element 15 is placed on the surface 21 of the mold base 22, the rough surface of the convex portion 16 of the optical element 15 is brought into contact with the surface 21 of the mold base 22.

  By placing the optical material 15 on the surface 21 of the trapezoid 22 in this way, there is a function of keeping the distance between the surface 21 of the trapezoid 22 and the rough surface of the convex portion 16 of the optical material 15 constant. It is preferable to place it.

However, the present invention is not limited to this. For example, the optical element 15 may be held on the mold table 22 by being separated from the surface 21 of the mold table 22 by approximately 0.1 mm by a holding member (not shown).
As shown in FIG. 3, the lower surface of the mold base 22 is disposed in contact with a heat plate 24 that houses a plurality of heat sources 23. As a result, the plurality of heat sources 23 are driven to generate heat, the heat plate 24 containing them is heated, and this heat is transmitted to the mold table 22 to heat the mold table 22. Then, the rough surface of the convex portion 16 of the optical element 15 is heated by the heated mold table 22, and the fine unevenness 12 on the surface layer of the large unevenness 11 of the convex portion 16 is melted. As shown in a) and (b), the surface is corrected to a rough surface consisting only of large irregularities 11.

  In this example, the distance between the trapezoid 22 serving as a heat transfer source and the optical element 15 made of glass material can be kept constant by the simplest method, and the rough portion of the convex portion 16 made of glass material having poor heat conduction can be maintained. Only the surface layer portion having a surface depth of about 40 μm can be uniformly heated and softened.

  Further, according to this method, since the inside of the rough surface of the convex portion 16 is not melted, the shape error Pv of the rough surface of the convex portion 16 and the large unevenness 11 of the surface layer portion is within 10 μm. The shape of the large unevenness can be maintained so as not to collapse.

By leaving such large irregularities, the amount of light can be improved by eliminating small irregularities without impairing the diffusion effect of incident light.
Note that there is no problem because the entire shape of the rough surface of the convex portion 16 is not deformed unless pressure is applied from above only by placement. Moreover, since it is surface layer heating and a heating period is also short, the whole shape of the rough surface of the convex part 16 does not deform | transform also in this point.
(Third embodiment)
By the way, if the rough surface of the convex portion 16 of the optical element 15 is merely placed on the surface 21 of the mold base 22 as described above, the optical element 15 may fall down, and the outer periphery thereof is suppressed by a ring. It is good to do so.

  In this case, the ring may be made of a cemented carbide or AlN having a good thermal conductivity. Otherwise, not only the rough surface layer portion of the convex portion 16 but also heat may be trapped inside the optical element 15 and melt into the optical element 15.

  If heating and cooling are performed too slowly in time, the entire material is heated and the entire material is softened, which may make it difficult to maintain the shape. Therefore, a rapid change in the temperature of the trapezoid prevents the entire material from being heated.

  Further, by preheating the entire optical element 16 with another heater prior to the melting of the surface layer portion, the entire temperature of the optical material 15 can be stabilized, and unstable cooling from the inside to the surface layer portion can be prevented. . Further, by adjusting the temperature of the heater, it is possible to finely adjust the melting depth of the surface layer portion.

  In order to realize the above, the mold base 22 holding the optical element 15 is transported and sequentially moved to at least three temperature-controlled molding rough surface correcting shafts, and the temperature of the base mold 22 is preheated → heated. → Change rapidly with cooling. This will be described below as a third embodiment.

  FIG. 4A is a cross-sectional view showing a mold base set and an optical element in the third embodiment, and FIG. 4B is a diagram schematically showing a rough surface correcting portion for correcting the rough surface. It is. The mold base set 25 shown in FIG. 1A includes a lower mold 27 having a rough surface correcting recess 26 formed at the center of the upper surface and having a stepped portion on the lower peripheral surface.

  Similarly to the surface 21 of the mold base 22 shown in FIG. 3, the rough surface correcting concave portion 26 of the lower mold 27 has a shape along the shape of the rough surface of the convex portion 16 of the optical element 15, and only the rough surface. It is a recessed part which has a surface of the shape which covers.

The inverted optical element 15 is placed in the rough surface correcting concave portion 26 with the rough surface of the convex portion 16 in contact with the concave portion.
A cylindrical sleeve 28 is engaged with a step portion on the lower peripheral surface of the lower mold 27 so as to be erected. An annular ring 29 is disposed inside the sleeve 28. The ring 29 has its outer peripheral surface abutted against the inner wall of the sleeve 28, and its lower surface is in close contact with the upper surface of the lower mold 27, and supports the optical element 15 so as not to fall down on the inner peripheral surface.

  In the rough surface correcting portion 30 shown in FIG. 3B, three rough surface correcting shaft portions 31 (31a, 31b, 31c) are arranged in order of steps from left to right. The rough surface correction shaft portion 31a serving as the first axis is a shaft portion for a preheating process, and the rough surface correction shaft portion 31b serving as the second axis is a shaft portion for a heating process for heating and melting the rough surface layer portion, The rough surface correction shaft portion 31c serving as the third shaft is a shaft portion for a cooling process.

  Each rough surface correcting shaft portion 31 has the same configuration except only the temperature adjustment temperature. That is, a fixed heat plate 34 that is fixed to the lower frame 32 of the shaft unit main body and includes a heater 33 is provided at the lower portion, and a movable heat plate 36 that includes a heater 35 is provided at the upper portion. The movable heat plate 36 is fixed to a lower end portion of a piston 38 that moves up and down from a cylinder device (not shown) fixed to the upper frame 37 of the shaft device body.

FIG. 5 is a diagram for explaining the rough surface correcting step of the rough surface correcting unit 31.
First, as shown in FIG. 5, a room temperature mold base set 25 on which the optical element 15 is placed on the lower mold 27 is conveyed as shown by an arrow a by an external conveyance mechanism (not shown), and the first axis It is supplied to the rough surface correcting shaft portion 31a that performs the preheating step. Then, the piston 38 of the rough surface correcting shaft portion 31 a advances downward, and moves down until the movable heat plate 36 contacts the upper end portion of the sleeve 28 of the mold base set 25.

  Heat is transmitted to the flat portion of the optical element 15 by radiation from the upper movable heat plate 36 and convection in the sleeve 28, and the flat portion side of the optical element 15 is preheated. In the lower part, the fixed heat plate 34 is in close contact with the lower surface of the lower mold 27 of the mold base set 25 to transmit heat to heat the lower mold 29, and the heat of the lower mold 29 is heated to the convex portion 16 of the optical element 15. And the convex portion 16 side of the optical element 15 is preheated. This preheating time is 20 seconds.

  In this preheating, when the material of the optical element 15 is “OHARA S-LAH58”, the strain point is 660 ° C., and preheating is performed at “660 ° C.−10 ° C. = 650 ° C.” which is 10 ° C. lower than the strain point.

  The optical element 15 is supported by a ring 29 that comes into contact with the peripheral surface of the optical element 15 protruding above the rough surface correcting recess 26 of the lower mold 27 so that the inverted state does not collapse. 29 is made of a material having good heat conduction as described above, so that there is no problem that heat is trapped inside the optical element 15 and the inside of the optical element 15 is unraveled.

  Subsequently, the piston 38 of the rough surface correcting shaft portion 31 a is raised, and the movable heat plate 36 is separated from the sleeve 28 of the mold base set 25 to open the mold base set 25. The released preheated optical element 15 and the mold base set 25 on which the optical element 15 is placed are conveyed as indicated by an arrow b and supplied to the rough surface correcting shaft portion 31b that performs the heating process of the second shaft. .

The piston 38 of the rough surface correcting shaft portion 31b advances downward and moves down until the movable heat plate 36 contacts the upper end portion of the sleeve 28 of the mold base set 25.
Also here, heat is transmitted to the flat portion of the optical element 15 by radiation from the upper movable heat plate 36 and convection in the sleeve 28, and the flat portion side of the optical element 15 is heated. In the lower part, the fixed heat plate 34 is in close contact with the lower surface of the lower mold 27 of the mold base set 25 to transmit heat to heat the lower mold 29, and the heat of the lower mold 29 is heated to the convex portion 16 of the optical element 15. The convex portion 16 side of the optical element 15 is heated. This heating time is 120 seconds.

  In this way, the rough surface correcting shaft portion 31b heats and melts the surface portion of the rough surface of the convex portion 16 of the preheated optical element 15. In this heating, when the softening point of the material of the optical element 15 is 803 ° C., the heating is performed at “803 ° C. + 97 ° C. = 900 ° C.” which is 97 ° C. higher than the softening point 803 ° C.

  Even if it is heated in this way, the shape of the optical element 15 is not greatly deformed by 2 μm or more without pressure or overheating, and only small irregularities with an arithmetic roughness Ra of 0.29 to 0.6 μm are melted.

  Next, the piston 38 of the rough surface correcting shaft portion 31b rises and the movable heat plate 36 is separated from the mold table set 25 to open the mold table set 25. The mold base set 25 on which the optical element 15 in which the small unevenness of the rough surface layer portion has been melted by the above heating is mounted is conveyed as shown by an arrow c, and the rough surface correction is performed to perform the cooling process of the third axis. It is supplied to the shaft portion 31c.

The piston 38 of the rough surface correcting shaft portion 31c advances downward, and moves down until the movable heat plate 36 contacts the upper end portion of the sleeve 28 of the mold base set 25.
The axial temperature of the rough surface correcting shaft portion 31c is “738 ° C.−238 ° C. = 500 ° C.”, which is 238 ° C. lower than the glass transition point 738 ° C. when the glass transition point of the optical element 15 is 738 ° C. At this temperature, the optical element 15 in which the small unevenness of the surface portion of the rough surface is melted by the heating is cooled. This cooling time is 30 seconds.

  Subsequently, the piston 38 of the rough surface correcting shaft portion 31c is raised, and the movable heat plate 36 is separated from the mold table set 25 to open the mold table set 25. The mold set 25 on which the opened cooled optical element 15 is placed is transported as indicated by an arrow d, transported to a room temperature room (not shown), and gradually cooled to room temperature.

  Thus, the resulting optical element 15 avoids heating to the inside of the material, and does not impair the overall shape by 2 μm or more, that is, without impairing the large uneven shape within the surface error Pv of 10 μm of the convex portion 16. Only small irregularities of Ra 0.29 μm to 0.6 μm on the surface of large irregularities disappear by melting.

  In this way, the small unevenness of the surface layer portion of the convex portion 16 is reduced or eliminated to suppress the occurrence of uneven light distribution as an irradiation element, while ensuring the light distribution performance by leaving the large unevenness, and the amount of transmitted light on the surface Can be improved.

  In addition, this invention is not limited to the said embodiment, In the implementation stage, it can change variously in the range which does not change the summary.

(a) is an enlarged view showing the optical element in the first embodiment, (b) is an enlarged view showing a portion surrounded by a broken-line circle b in (a) of the convex portion of the optical element. is there. It is a figure which shows the basic manufacturing method of the optical element in 1st Embodiment. It is a figure explaining the correction method of the rough surface of the optical element in 2nd Embodiment. (a) is sectional drawing which shows the mold base set and optical element in 3rd Embodiment, (b) is a figure which shows typically the rough surface correction part which corrects a rough surface. It is a figure explaining the rough surface correction process of the rough surface correction part in 3rd Embodiment. (a), (b) is a figure which shows two examples of the shape of the optical element of the light source in the conventional illumination optical systems, such as an endoscope. (a) is an enlarged view of the lens shown in FIG. 6 (a), and (b) is an enlarged view of a portion surrounded by a broken line circle a in (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Outgoing light 3 Outlet 4 Lens 5 Convex part 6 Irradiation light 7 Plane part 8 Lens 9 Internal reflection surface 10 Plane part 11 Lens 12 Convex part 15 Optical element 16 Convex part 17 Plane part 18 Jig 19 Heat source 20 Heat plate 21 surface 22 stand type 23 heat source 24 heat plate 25 type stand set 26 rough surface correction recess 27 lower die 28 sleeve 29 ring 30 rough surface correction portion 31 (31a, 31b, 31c) rough surface correction shaft portion 32 shaft Lower part device body frame 33 Heater 34 Fixed heat plate 35 Heater 36 Movable heat plate 37 Shaft part body upper frame 38 Piston

Claims (5)

  Heating a rough surface having a function of scattering light among a plurality of functional surfaces of the optical element, dissolving the fine unevenness of the surface layer of the large unevenness of the rough surface to form a rough surface consisting only of the large unevenness, A method for manufacturing an optical element.   A mold base having a shape that covers only the rough surface in a shape along the shape of the rough surface, and the optical element is brought into contact with or close to the rough surface of the optical element. 2. The method of manufacturing an optical element according to claim 1, wherein the mold table is held, the mold table is heated, and the rough surface is heated through the mold table.   3. The optical element according to claim 2, wherein the optical element is held on the mold table by placing the rough surface of the optical element on the surface of the mold table or by separating the rough surface from the surface by approximately 0.1 mm. Manufacturing method.   4. The method of manufacturing an optical element according to claim 3, wherein an outer periphery of the optical element is held by a ring and the optical element is held on the mold base.   The mold table holding the optical element is transported and sequentially moved to at least three temperature-controlled molding rough surface correcting shafts, and the temperature of the mold is rapidly changed from preheating → heating → cooling. 5. The method of manufacturing an optical element according to claim 1, 2, 3 or 4.