JP2019000957A - Lens polishing device and lens polishing method - Google Patents

Abstract

To provide a polishing device capable of performing processing of a spherical lens having a small curvature and a small diameter with good accuracy, in a state where abrasion of solid abrasive grains is suppressed.SOLUTION: In a polishing device 1, a pressing shaft 16 of a pressing mechanism 13 for pressing a lens 11 to be processed held in a lens holder 12 to a lens machining dish 5 is guided in an upper shaft central axis line 3a direction by a linear guide mechanism 18. The linear guide mechanism 18 includes two pairs of guide parts 32, 33. Each of the guide parts 32, 33 includes three ball bearings 41-43 arranged at positions with equally angled intervals around an upper shaft central axis line 3a so as to surround the pressing shaft 16. Each of the ball bearings 41-43 is in a rolling contact with a circular outer peripheral surface 16a of the pressing shaft 16 in a state where a preload is acting in a direction toward the central axis line 3a in a direction orthogonal to the upper shaft central axis line 3a.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lens polishing apparatus and a lens polishing method, and more particularly to a small curvature / small diameter lens polishing apparatus and a lens polishing method suitable for processing a lens spherical surface of a small diameter small diameter lens having a curvature radius of 5 mm or less.

  As a lens polishing apparatus, for example, a spherically oscillating lens spherical surface polishing apparatus is known in which a lens processing dish is swayed in a spherical state while pressed against a lens to be processed to polish a lens spherical surface. In such a lens polishing apparatus, the lens holder holding the lens to be processed is pressed against the lens processing dish using the pressing shaft of the pressing mechanism linearly guided by the linear guiding mechanism.

  FIG. 3 is an explanatory view showing a linear guide mechanism for linearly guiding the pressing shaft in the lens polishing apparatus. As shown in this figure, the linear guide mechanism 100 includes a cylindrical shaft holder 101, and a pressing shaft 102 of the pressing mechanism penetrates in a coaxial state. Sliding bearings formed by cylindrical bushes 103 and 104 are arranged on the inner peripheral surfaces of the upper and lower ends of the shaft holder 101. The pressing shaft 102 is slidably supported by a sliding bearing in the vertical direction along the central axis line 102a. A holder shaft 106 of the lens holder 105 is attached to the lower end portion of the pressing shaft 102 in a coaxial state in a rotatable state. A lower-axis ball center oscillating type polishing machine provided with such a linear guide mechanism composed of a sliding mechanism has been proposed, for example, in Patent Document 1 by the applicant of the present application.

JP 2004-298985 A

  In recent years, spherical lenses having a small curvature and a small diameter are increasingly required as lenses for portable communication terminals and in-vehicle cameras. However, it is difficult to accurately process the spherical surface of a small curvature / small diameter lens for the following reason.

  First, the lens processing surface of the processing dish for lens polishing also has a small curvature according to the lens to be processed. In general, a polishing urethane pad used for lens polishing is difficult to affix to a lens processing surface (lens polishing surface) with a small curvature, and there is no appropriate polishing tool.

  For this reason, it is necessary to use the processing dish provided with the abrasive surface using a solid abrasive grain etc., without using a urethane pad. However, since fixed abrasive grains are easily worn, it is necessary to reduce the pressing force of the lens to be processed against the processing plate during processing and to reduce the lost motion of the pressing.

  However, in a conventional lens spherical polishing apparatus, for example, a lower-axis spherical center oscillation type polishing machine, a sliding mechanism is used for linear guide of a pressing shaft for pressing a lens holder. Since the sliding mechanism has a large sliding resistance and a large lost motion, it is difficult to press the lens to be processed against the lens processing surface of the solid abrasive grains in an appropriate state with a small pressing force.

  In addition, when processing a lens with a small curvature, the mechanical accuracy must be increased in proportion to the small curvature. However, a sliding bearing, for example, a sliding mechanism for linearly guiding a pressing shaft using a metal bush, requires an appropriate clearance at the sliding contact portion between the pressing shaft and the metal bush. Due to this clearance, play occurs in the sliding contact portion. For this reason, the accuracy for matching the center axis of the lens holder, that is, the center axis of the pressing shaft that is linearly guided by the sliding mechanism, with the center of swinging of the spherical center of the processing plate is maintained at a high accuracy of 10 microns or less. Is difficult.

  An object of the present invention is to propose a lens polishing apparatus and a lens polishing method capable of accurately processing a spherical lens having a small curvature and a small diameter in a state where wear of solid abrasive grains is suppressed.

The lens polishing apparatus suitable for processing the small curvature / small diameter lens of the present invention is:
A lens processing dish having a lens processing surface of a predetermined curvature;
A rocking mechanism for rocking the lens processing dish about the center of curvature of the lens processing surface;
A lens holder for holding the lens to be processed;
A pressing mechanism having a pressing shaft coaxially connected to the lens holder in order to press the lens to be processed held by the lens holder against the lens processing surface of the processing plate;
A linear guide mechanism for guiding the pressing shaft in the direction of its central axis,
The linear guide mechanism is
Two sets of guide portions arranged at positions away from each other in the direction of the central axis of the pressing shaft;
Each of the guide portions includes three rolling bearings arranged at equiangular intervals around the central axis so as to surround the pressing shaft,
Each of the rolling bearings is in rolling contact with the outer peripheral surface of the pressing shaft in a state in which preload is applied in a direction toward the central axis along a direction orthogonal to the central axis.

  In the lens polishing apparatus of the present invention, the pressing shaft is supported in a rolling contact state from the outer peripheral side by three rolling bearings at two positions separated in the direction of the central axis. Compared with the case where the pressing shaft is linearly guided in the sliding contact state, the sliding resistance when pressing the pressing shaft can be reduced, and the lost motion can be reduced. The pressing force of the lens processing dish against the lens to be processed can be reduced. For example, the minimum pressing force can be reduced to 3N. As a result, it is possible to easily suppress excessive wear of the solid abrasive grains during polishing using the lens processing dish using the solid abrasive grains.

  Further, in the present invention, a preload is applied to each rolling bearing so that no gap is generated in the rolling contact portion between the rolling bearing and the pressing shaft. There is no gap between the pressing shaft and each rolling bearing that linearly guides the pressing shaft. The center axis of the pressing shaft can be accurately held at a position passing through the center of oscillation of the lens processing plate. Therefore, the accuracy for matching the center axis of the lens holder holding the workpiece lens with the oscillation center of the processing plate can be maintained at a high accuracy of 10 microns or less.

In order to polish a lens spherical surface having a small curvature with a radius of curvature of 5 mm or less using the lens polishing apparatus having the above configuration, in the lens polishing method of the present invention,
Set the preload for each of the rolling bearings so that the center axis of the pressing shaft (lens holder) and the center of curvature of the lens processing surface of the lens processing pan coincide with each other with an accuracy of 10 microns or less,
The minimum value of the pressing force of the processing lens against the lens processing surface of the lens processing pan by the pressing mechanism is set to 3N.

  According to the lens polishing apparatus and the lens polishing method of the present invention, spherical polishing of a small-diameter lens having a small radius of curvature of 5 mm or less mounted on a portable communication terminal such as a mobile phone, an in-vehicle camera, etc. It can be performed with high accuracy in a state where grain wear is suppressed.

It is a schematic block diagram which shows the lower shaft ball center rocking | polishing type | mold polishing apparatus suitable for the process of the small curvature and a small diameter lens to which this invention is applied. It is explanatory drawing which shows the linear guide mechanism of FIG. 1, and its guide part. It is explanatory drawing which shows the linear guide mechanism of the conventional press shaft.

  In the following, an embodiment of a lens polishing apparatus suitable for processing a small curvature / small diameter lens to which the present invention is applied will be described with reference to the drawings. The lens polishing apparatus described below relates to a lower-axis spherical center oscillation type polishing apparatus, but the present invention is not limited to the lower-axis spherical center oscillation type polishing apparatus.

  FIG. 1 is a schematic configuration diagram showing a lower-axis ball center oscillation type polishing apparatus according to the present embodiment. A lower shaft ball center oscillating polishing apparatus 1 (hereinafter simply referred to as “polishing apparatus 1”) includes a lower shaft unit 2, an upper shaft unit 3, and a control panel 4 that controls driving of each part. ing.

  The lower shaft unit 2 includes a lens processing plate 5, a spindle 6, a spindle case 7, and a ball center swing mechanism 8. The lens processing plate 5 includes a lens processing surface 5a having a predetermined curvature. The lens processing plate 5 is coaxially fixed to the upper end portion of the spindle 6 so that the lens processing surface 5a faces upward. The spindle 6 is supported in a freely rotatable state by a spindle case 7. The lens processing surface 5a of the lens processing plate 5 of this example is a grinding surface formed from, for example, solid abrasive grains.

  A spindle motor (not shown) disposed in the spindle case 7 rotates the spindle 6 and therefore the lens processing plate 5 around the lower axis center axis 2a passing through the center of the lens processing surface 5a. The spindle case 7 is supported by a ball center swing mechanism 8. By the ball center swing mechanism 8, the lens processing plate 5 performs a ball center swing motion with the center of curvature of the lens processing surface 5a located on the lower axis central axis 2a as the swing center O.

  The upper shaft unit 3 includes a lens holder 12 that holds the workpiece lens 11, a pressing mechanism 13 that presses the lens holder 12, and a lifting stage 14 that lifts and lowers the lens holder 12. The lens holder 12 includes a lens holding surface 12a at the lower end for holding the processed lens surface 11a of the processed lens 11 in a downward state. A holder shaft 12 b extends coaxially upward from the center of the upper end surface of the lens holder 12. The center axis of the lens holder 12 is the upper axis center axis 3a.

  The pressing mechanism 13 includes a pressing shaft 16 and a pressing portion 17 that applies a pressing force to the pressing shaft 16. The pressing shaft 16 is linearly guided by the linear guide mechanism 18. That is, the pressing shaft 16 is vertically supported so that the center axis thereof coincides with the upper axis central axis 3a, and is linearly guided in the direction of the upper axis central axis 3a. A holder shaft 12b of the lens holder 12 is connected to the lower end portion of the pressing shaft 16 in a coaxial state and a rotatable state. The pressing portion 17 includes a pressing spring 19 for pressing the pressing shaft 16 downward along the direction of the upper axis central axis 3a, and a pressing knob 20 for adjusting the pressing force by the pressing spring 19. Yes. Instead of the pressing spring 19, an air cylinder for pressing can be used.

  The pressing mechanism 13 and the linear guide mechanism 18 are supported by the elevating stage 14 via the support bracket 21. The elevating stage 14 can be moved up and down along a vertical stage guide 23 attached to a fixedly installed stage frame 22. The elevating stage 14 is raised and lowered by an elevating air cylinder 24 attached to the stage frame 22. A servo motor can also be used as a drive source for raising and lowering.

  FIG. 2 shows the linear guide mechanism 18, FIG. 2 (a) is an explanatory view showing a state in which a part is cut and the internal structure is known, and FIG. 2 (b) is an explanatory view showing the upper guide portion. It is.

  The linear guide mechanism 18 includes a cylindrical shaft holder 31, and a pressing shaft 16 extends through the hollow portion of the shaft holder 31 in a coaxial state. Further, the linear guide mechanism 18 includes two sets of guide portions 32 and 33 attached to the upper and lower ends of the shaft holder 31 in order to linearly guide the pressing shaft 16 in the vertical direction. Since the upper and lower guide portions 32 and 33 have the same configuration, only the upper guide portion 32 will be described. In FIG. 2, the reference numerals given to the respective parts in the guide part 32 are given to the corresponding parts in the lower guide part 33. In addition, description of each part in the guide part 33 is abbreviate | omitted.

  In this example, the shaft holder 31 is a holder having a circular cross section, and the guide portion 32 includes three rolling bearings arranged to surround the shaft holder 31, in this example, ball bearings 41, 42, and 43. . The ball bearings 41 to 43 are arranged at equiangular intervals (120 ° intervals) with the upper axis central axis 3a as the center. A rolling bearing such as a roller bearing may be used instead of the ball bearing.

  At the upper end of the shaft holder 31, annular bearing mounting flanges 44 and 45 are formed at regular intervals in the vertical direction. Between the bearing mounting flanges 44 and 45, there are formed three pairs of support plates 51 to 53 arranged at equal angular intervals with the upper shaft center axis 3a as the center. Bearing support shafts 61 to 63 are fixed to the support plates 51 to 53, respectively. The bearing support shafts 61 to 63 are such that their support shaft center lines are positioned on an orthogonal plane orthogonal to the upper shaft center axis 3a and extend in a direction orthogonal to the radial direction centering on the upper shaft center axis 3a. Are attached to each of the support plates 51 to 53.

  Inner rings of ball bearings 41 to 43 are coaxially fixed to the bearing support shafts 61 to 63. The circular outer peripheral surfaces of the outer rings 41 b to 43 b of the ball bearings 41 to 43 are in rolling contact with the circular outer peripheral surface 16 a of the pressing shaft 16. In this example, the circular outer peripheral surfaces of the ball bearings 41 to 43 are just displaced slightly to the center side from the position where the state of contact with the circular outer peripheral surface 16a of the pressing shaft 16 is formed. Ball bearings 41 to 43 are arranged.

  Accordingly, the ball bearings 41 to 43 are brought into rolling contact with the circular outer peripheral surface 16a of the pressing shaft 16 in a state where a predetermined preload is applied. That is, the state where the play between the inner ring, the outer rings 41b to 43b, and the balls, which are the components of the ball bearings 41 to 43, is removed is formed, and the pressing shaft 16 is linearly guided vertically without rattling. The Therefore, it is possible to accurately maintain a state where the swing center on the lower shaft unit 2 side is positioned on the upper shaft center axis 3a.

  In the polishing apparatus 1 having this configuration, first, the lens 11 to be processed is held on the lens holding surface 12a of the lens holder 12 in the upper shaft unit 3 by means such as vacuum suction. Next, the air cylinder 24 is operated to lower the elevating stage 14 to press the processed lens surface 11 a of the processed lens 11 against the lens processed surface 5 a of the lens processing plate 5 of the lower shaft unit 2. By adjusting the pressurizing knob 20, it is possible to adjust the pressing force by the pressing spring 19 that is mounted in a compressed state between the pressing knob 20 and the upper end of the pressing shaft 16. In a state where the lens to be processed 11 is pressed against the lens processing surface 5a (polishing surface) of the lens processing plate 5, the lens processing plate 5 is rotated and the centroid is swung to process the lens 11 to be processed.

  The present inventors performed spherical polishing of a small-diameter lens having a small curvature with a radius of curvature of 5 mm or less using a lens processing dish 5 using solid abrasive grains in the polishing apparatus 1. It was confirmed that the minimum pressing force of the lens 11 to be processed on the lens processing plate 5 can be 3N. In addition, it was confirmed that the upper shaft center axis 3a (the center shaft line of the pressing shaft) and the swing center O of the lower shaft unit 2 can be maintained in a state of matching with an accuracy of 10 microns or less. It was confirmed that the abrasion of the solid abrasive grains on the lens processing dish 5 can be suppressed, and the spherical polishing of the small curvature / small diameter lens can be easily performed.

1 Polishing device (lower axis ball center oscillation type polishing device)
2 Lower shaft unit 2a Lower shaft center axis 3 Upper shaft unit 3a Upper shaft center axis 4 Control panel 5 Lens processing plate 5a Lens processing surface 6 Spindle 7 Spindle case 8 Ball center swing mechanism 11 Processing lens 11a Processing lens surface 12 Lens holder 12a Lens holding surface 12b Holder shaft 13 Pressing mechanism 14 Lifting stage 16 Pressing shaft 16a Circular outer peripheral surface 17 Pressing part 18 Linear guide mechanism 19 Pressing spring 20 Pressing knob 21 Support bracket 22 Stage frame 23 Vertical stage guide 24 Air cylinder 31 Shaft holder 32 Guide part 33 Guide part 41 Ball bearing 41b Outer ring 42 Ball bearing 42b Outer ring 43 Ball bearing 43b Outer ring 44 Bearing mounting flange 45 Bearing mounting flange 51 Support plate 52 Support plate 53 Support plate 61 Beared Grayed shaft 62 bearing shaft 63 a bearing shaft O swinging center

Claims (3)

A lens processing dish having a lens processing surface of a predetermined curvature;
A rocking mechanism for rocking the lens processing dish about the center of curvature of the lens processing surface;
A lens holder for holding the lens to be processed;
A pressing mechanism having a pressing shaft coaxially connected to the lens holder in order to press the lens to be processed held by the lens holder against the lens processing surface of the lens processing plate;
A linear guide mechanism for guiding the pressing shaft in the direction of the central axis,
The linear guide mechanism is
Two sets of guide portions arranged at positions away from each other in the direction of the central axis of the pressing shaft;
Each of the guide portions includes three rolling bearings arranged at equiangular intervals around the central axis so as to surround the pressing shaft,
Each of the rolling bearings is a lens polishing apparatus that is in rolling contact with the outer peripheral surface of the pressing shaft in a state in which preload is applied in a direction toward the central axis along a direction orthogonal to the central axis. In claim 1,
The lens polishing apparatus, wherein the lens processing surface of the lens processing dish is a solid abrasive surface. A lens polishing method for polishing a lens spherical surface having a small curvature with a radius of curvature of 5 mm or less using the lens polishing apparatus according to claim 2,
A preload for each of the rolling bearings is set so that the center axis and the center of curvature of the lens processing surface of the lens processing plate coincide with each other with an accuracy of 10 microns or less;
A lens polishing method in which a minimum value of the pressing force of the lens to be processed against the lens processing surface of the lens processing dish by the pressing mechanism is set to 3N.

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