JP2013193146A - Misalignment detector for lens and lens centering and edging machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a misalignment detector for lens that detects misalignment of the optical axis of a lens being in or after outer circumference processing from the axis and center of rotation of a holder holding the lens, and a lens centering and edging machine with the detector.SOLUTION: A misalignment detector for lens includes a rotary pedestal on which a lens is mounted, a freely rotatable press ring which is provided above the pedestal and holds the lens L on the pedestal with the pedestal 1 when moving down, and an optical measuring instrument which detects the lens tilting on the pedestal by receiving reflected light of a light beam projected on the lens on the pedestal through a center hole of the press ring. The optical measuring instrument images the reflected light of the light beam projected on the lens from above on a two-dimensional image receiving element, and then measures the direction and amount of eccentricity of the reflected light with the reflected light of the projection light at the imaging position.

Description

  The present invention relates to a lens misalignment detector that detects a deviation between an optical axis of a lens and an axis or a rotation center of a cradle on which the lens is placed, and a lens centering machine including the detector. .

  The lens performs spherical processing on the front and back surfaces, and then performs peripheral processing on the basis of the optical axis determined by the processed spherical surface. An apparatus for processing the outer periphery of the lens with reference to this optical axis is called a centering machine. A general centering machine controls a holder that rotates while holding a lens, a rotating grindstone that moves closer to and away from the outer periphery of the lens held by the holder, and a moving position of the rotating grindstone in the approaching and separating direction. NC controller. Since the NC controller sets the position of the rotating grindstone with reference to the axis or rotation center of the holder, in order to perform accurate outer periphery machining, the lens to be machined as the premise is that its optical axis is the center of rotation of the holder. It is necessary to be held in exact alignment (centered).

  As a method of centering the lens on the holder, the upper and lower bell cups are synchronously driven to rotate while the holder is formed by the upward and downward bell cups having a perfect circle edge and the lens is lightly held vertically by the holder. Method, rotating the holder holding the lens by a predetermined angle, measuring the position of the peripheral part of the lens spherical surface at each rotation position with a dial gauge, and the direction and amount of eccentricity between the lens optical axis and the axis of the holder Is calculated, the eccentric direction is directed to the grinding wheel for outer peripheral grinding, and the lens is pushed by a distance corresponding to the eccentric amount with the grinding wheel. The applicant of the present application has proposed a new centering means in Japanese Patent Application No. 2011-237377.

  After centering the lens on the holder as described above, the lens centering machine performs peripheral grinding of the lens with a grindstone while rotating the holder. In order to prevent the lens from moving on the holder due to processing reaction force during this peripheral grinding, processing is performed by firmly adsorbing the lens on the holder with negative pressure, or pressing down like the downward bell cup described above Processing is performed by holding the lens between the members. However, since there is a risk of damaging the lens, the clamping force cannot be increased so much that the lens may move on the holder during processing and cause misalignment.

  Conventionally, it is not possible to detect on the centering machine whether or not the lens being processed or processed has been misaligned on the holder, and the optical axis of the lens coincides with the center of the lens outer periphery in the subsequent process. The lens that caused the misalignment was discarded as a defective product.

  The present invention eliminates the above-described problems, and highly accurately shifts the optical axis of a lens being processed or processed on a centering machine and the axis or rotation center of a holder supporting the lens. It is an object of the present invention to provide a misalignment detector that can detect and a lens centering machine equipped with such a detector.

  The lens misalignment detector according to the present invention is provided between a cradle 1 on which a lens L is placed and a cradle 1 that is provided above the cradle so that the lens L on the cradle 1 can be moved up and down. And receiving the reflected light 33 of the light beam 31 projected on the lens L on the cradle through the center hole 21 of the squeeze ring and receiving the eccentricity (tilt) of the lens on the cradle. And an optical measuring instrument 3 for detection. The cradle 1 and the holding ring 2 form a holder for holding the lens with the optical axis of the lens L aligned with the main axis a.

  The optical measuring instrument 3 reflects the light beam 31 projected from above the lens L placed on the cradle 1 as a light spot on the lens surface, and forms an image of the reflected light 33 on the two-dimensional light receiving element 35. Then, the eccentric direction and the eccentric amount e of the reflected light 33 with respect to the projection light 31 are measured at the imaging position.

  The cradle 1 is rotationally driven around the spindle axis a. The holding ring 2 is connected to an elevating drive device through a bearing 22 and an elevating table 23 each having a hollow hole through which the light beam 31 and its reflected light 33 pass, so that it can freely rotate around its central axis. Yes.

  The lens L is sandwiched between the cradle 1 and the pressing ring 2. When the cradle 1 is rotated in this state, the lens L and the pressing ring 2 are driven to rotate, and the reflected light 33 of the light beam 31 projected onto the lens L is circular on the light receiving element 35 of the optical measuring instrument. Draw a trajectory c. The misalignment detector 30 measures the eccentric direction of the lens L on the cradle 1 from the positional relationship between the center p of the circular locus and the light receiving point s when the cradle 1 is stopped, and the diameter of the circular locus. From the above, the eccentricity e of the lens is measured.

  By providing the misalignment detector 30 of the present invention and the centering means 4 for aligning the optical axis of the lens L placed on the cradle with the center or the center of rotation of the cradle 1 before and during processing. When a deviation (bias) between the optical axis of the lens L on the cradle 1 and the center of rotation of the cradle 1 can be detected at any timing after machining and a misalignment that can be corrected occurs during machining. In addition, it is possible to obtain a lens centering machine capable of correcting the deviation and continuing the processing.

  According to the present invention, the lens misalignment of the lens on the cradle 1 can be detected at any timing during and after processing, as well as before processing. Further, since the center deviation of the lens can be detected while the cradle 1, the lens L, and the holding ring 2 holding the lens are rotating, the processing is stopped for detection or the rotation of the cradle 1 is stopped. There is no need to reduce the machining efficiency.

  If a lens misalignment is detected during processing, the processing can be temporarily stopped to correct the misalignment and rework can be performed. If correction is impossible, the lens can be discarded during the processing. Further, if a misalignment is detected in the processed lens, the defective lens can be discarded at that time, and a misalignment measuring step in a later process becomes unnecessary.

  Further, as shown in the illustrated embodiment, the holding ring 2 is a free rotating body with a small mass that is rotated by the frictional force from the lens on the cradle 1 so that the upper cup is synchronously driven as in the conventional bell cup system. A system is not required, and the lens pressing force can be controlled more accurately.

The block diagram which shows the Example of the centering machine provided with the centering deviation detector of this invention Front view showing the misalignment detector of the centering machine of FIG. Explanatory drawing showing exaggerated lens decentering and reflected light shake The figure which shows the light receiving point on the two-dimensional light receiving element of the autocollimator

  FIG. 1 is a schematic front view showing an example of a lens centering machine provided with a misalignment detector of the present invention. The lens centering machine shown in the figure includes a main shaft 11 that is driven to rotate about a vertical axis (main shaft axis) a, an upward cup-shaped cradle 1 fixed to the upper end of the main shaft, and an upper portion of the cradle. The presser ring 2 is disposed, and a rotating grindstone 47 that processes the outer periphery of the lens L held and held between the cradle 1 and the presser ring 2 is provided. The presser ring 2 can freely move up and down and can freely rotate around the spindle axis a. The spindle 11 and the cradle 1 fixed to the upper end thereof are rotationally driven by a spindle motor 12.

  The main shaft 11 is a hollow shaft, and the hollow hole 13 communicates with the cup of the cradle 1. A lower end of the hollow hole 13 of the main shaft is connected to an air pressure supply device 5 for floating the lens on the cradle 1. The air pressure supply device 5 includes a pressure setting device 51, and air passing through the pressure setting device is supplied into the cradle 1 through the switching valve 52, the rotary joint 53, and the hollow hole 13 of the main shaft 11. It has become.

  The misalignment detector 30 projects a light beam 31 in the axial direction of the main axis to the lens L on the cradle 1 through the center 1 of the cradle 1 and the retaining ring 2 and the retaining ring 2 having the above structure, and the light beam An optical measuring instrument (autocollimator) 3 that receives the reflected light 33 through the center hole of the holding ring 2 is configured.

  The presser ring 2 has a lower surface made of synthetic resin and is attached by fitting an upper cylindrical portion to an inner ring of the ball bearing 22. The outer ring of the ball bearing 22 is fitted in a through hole in the vertical direction centering on the spindle axis a provided on the lifting platform 23. The lifting platform 23 is fixed to the head end side of the body 25 of the lifting cylinder 24. The cylinder body 25 is guided by a cylinder guide 26 (FIG. 2) in the direction of the spindle axis a so that the cylinder body 25 can freely move up and down, and the tip 27 of the rod is connected to the stationary position of the machine frame. That is, by supplying fluid pressure to the lift cylinder 24, the presser ring 2 supported so as to be freely rotatable by the lift base 23 when the cylinder body 25 is lifted and lowered is placed on the receiving base 1. The lens L is sandwiched between the cradle 1.

  The autocollimator 3 which is an optical measuring instrument is arranged above the lifting platform 23 with its optical axis as the same axis as the main axis a. The autocollimator 3 is gripped by a clamper 29 provided on a guide rail 28 in the direction of the main axis axis a so as to be able to move up and down, and can be adjusted in focus by moving and positioning in the optical axis direction by a lifting device (not shown).

  FIG. 1 schematically shows the internal structure of the autocollimator 3. The autocollimator 3 includes a projector 32 that projects a light beam 31 toward the lens L on the cradle 1, and a two-dimensional light receiving element 35 that receives reflected light 33 from the lens L by being reflected by a half mirror 34 at a right angle. It has. The light beam projected from the projector 32 irradiates the surface of the lens L as a light spot (focal point), the reflected light 33 forms an image on the light receiving surface of the light receiving element 35, and the position information is an electrical signal. Is output. The hollow hole 21 of the holding ring 2 is a through hole for allowing the light beam 31 and the reflected light 33 to pass therethrough.

  If the optical axis of the lens L and the axis of the cradle 1 are decentered, the lens tilts as shown in FIG. This inclination increases as the curvature of the lower surface of the lens in contact with the circular edge 14 of the cradle 1 increases, and the direction of inclination is reversed depending on whether the surface is convex or concave. At the center of the optical axis of the lens, the lens surface is perpendicular to the optical axis, and the light beam projected thereon is reflected in the incident direction. When the lens is decentered and tilted, the reflected light deviates from the incident light, and the position of the light receiving point s on the light receiving element 35 is shifted as shown in FIG. Draw a circular locus c.

  The center p of this circular locus is a point on the light receiving surface corresponding to the principal axis a. If the eccentric direction and the eccentric amount (radius of the circle) e of the light receiving point s are measured with the center point p as the origin, even if the origin o of the light receiving surface of the autocollimator 3 is deviated from the rotation center of the cradle 1. It is possible to measure the exact eccentric direction and the eccentric amount. While the outer periphery is being processed, that is, while the cradle 1 is rotating, the eccentric direction of the light receiving point s cannot be measured, but the eccentric amount e can be measured. Accordingly, the eccentricity e is monitored during the outer periphery machining, and when the eccentricity e exceeds the threshold value (allowable value) set in the NC controller, the spindle rotation is stopped and the eccentricity is stopped. If the center amount e can be corrected and is necessary for re-centering, the eccentric direction may be measured.

  The apparatus shown in FIG. 1 includes a pusher 4 that corrects misalignment by pushing the lens L in the radial direction on the cradle 1. The lens pusher 4 is made of synthetic resin and is mounted on the movable table 41 via the piezoelectric element 44. The moving table 41 is connected to a feed screw 42 via a ball nut (not shown), and this feed screw is rotationally driven by a feed motor 43 that is servo-controlled by the NC controller 6.

  The NC controller 6 determines the optical axis of the lens L from the center of rotation of the cradle 1 on the basis of the detection signal of the autocollimator 3 and the previously inputted unevenness of the lower surface of the lens (the eccentric direction is 180 degrees opposite). Based on the measured value of the eccentricity e of the autocollimator 3 and the phase control means 61 for controlling the rotation angle of the spindle motor 12 so that the eccentric direction faces the pusher 4. Stroke control means 62 for controlling the rotation angle of the feed motor 43 is provided.

  An AC power supply 45 is connected to the piezoelectric element 44 for vibrating it in the moving direction of the moving table 41. The NC controller 6 controls an on / off switch 46 of an AC power supply 45 that vibrates the piezoelectric element 44.

  In the above-described centering machine, when the lens L is carried onto the cradle 1 with the holding ring 2 moved upward, the autocollimator 3 irradiates the light beam 31 on the lens L and reflects the reflected light. Light is received by the two-dimensional light receiving element 35. Next, the main shaft 11 is slowly rotated to draw a circular locus c at the light receiving point s on the light receiving element 35, and the eccentric amount of the lens L with respect to the rotation center of the cradle 1 is measured from the radius of the circle. Next, the spindle 11 is stopped, and the eccentric direction is detected from the relative positional relationship between the center of the circle and the light receiving point s when the cradle 1 is stopped.

  The NC controller 6 gives a rotation command to the spindle motor 12 so that the detected eccentric direction faces the pusher 4. Next, the NC controller gives a forward command to the feed motor 43. When the movement start signal of the light receiving point s is received from the autocollimator 3 during this forward movement, it is determined that the pusher 4 has come into contact with the outer periphery of the lens L, and a measurement start command is given to the stroke control means 62. The stroke control means 62 stops the feed motor 43 at a position where the pusher 4 has been advanced by the eccentric amount e that has already been measured from the position of the pusher 4 when the measurement start command is given.

  When pushing the lens L with the pusher 4, the vibration feed can be selected by turning on the switch 46 of the AC power supply 45 as necessary. When the lens is heavy, air pressure is supplied from the air pressure supply device 5 to the cradle 1 to reduce the load on the lens acting on the cradle 1, thereby reducing the friction load when the lens is pushed and pushing the lens L. can do. The vibration feed is effective in preventing the lens L from moving beyond its stop position due to a so-called stick-slip phenomenon.

  When the pusher 4 pushes the lens L, the lens L may move in a direction deviated from the forward direction of the pusher 4 during the push, and the lens may move excessively due to inertia. Therefore, after the pushing operation is finished, the optical measuring instrument 3 confirms the eccentricity of the lens L, and if it is within a predetermined error range (threshold), the outer periphery machining is started. The centering operation is repeated by measuring the eccentric direction and the eccentric amount.

  When the centering of the lens is completed as described above, the holding ring 2 is moved downward to hold the lens L between the cradle 1 and the holding ring 2, and the spindle 11 is rotated by the spindle motor 12 to center the lens L. Rotate around the optical axis. Then, the rotating grindstone 47 is rotated, and the grindstone head 48 is advanced by a grindstone feed motor (not shown) so that the outer circumferential shape of the lens becomes a predetermined shape, so that the outer circumference of the lens is processed based on the optical axis of the lens L. .

  During this outer periphery processing, the autocollimator 3 irradiates the light beam 31 onto the lens L and continues to receive the reflected light by the two-dimensional light receiving element 35. If the lens L is misaligned during processing, the light receiving point s starts to draw a circular locus c on the light receiving element 35. If the radius of the circle exceeds the threshold value registered in the NC controller 6, the spindle 11 is stopped, and the eccentric direction is detected from the relative positional relationship between the center of the circle and the light receiving point s when the cradle 1 is stopped.

  If the measured amount of eccentricity e is a correctable amount, the NC controller 6 moves up the holding ring 2 and rotates the spindle motor 12 so that the detected eccentric direction faces the pushing body 4. After the lens L is pushed by the eccentric amount e detected by the pusher 4 and re-centering is performed, the presser ring 2 is lowered and the outer peripheral grinding process is resumed. If the eccentricity is an uncorrectable amount, the lens is discharged from the centering machine.

DESCRIPTION OF SYMBOLS 1 Receiving stand 2 Holding ring 3 Optical measuring instrument 4 Pushing body 6 NC controller 21 Center hole 22 Bearing 23 Lifting stand 24 Cylinder 30 Misalignment detector 31 Light beam 32 Emitter 33 Reflected light 35 Light receiving element 61 Phase control means 62 Stroke control Means a Spindle axis c Circular locus L Lens p Center of circular locus s Light receiving point

Claims (6)

A cradle for placing the lens with the optical axis as the center;
A holding ring that can be moved up and down above the cradle and clamps the lens on the cradle with the cradle when lowered,
A lens core comprising an optical measuring device that receives the reflected light of the light beam in the central axis direction projected on the lens on the cradle through the center hole of the holding ring and detects the tilt of the lens on the cradle. Deviation detector.   The optical measuring instrument reflects the light beam projected from above the cradle as a light spot on the lens surface, forms an image of the reflected light on the two-dimensional light receiving surface, and reflects the reflected light with respect to the projected light at the imaging position. The misalignment detector according to claim 1, wherein an eccentric direction and an eccentric amount are detected.   A lifting drive device that can freely rotate around the central axis via the receiving table that is rotationally driven around a central axis, and a bearing and a lifting platform that each include a through hole through which the light beam and reflected light pass. The misalignment detector according to claim 1, further comprising the presser ring that is connected.   By rotating the cradle with the lens held between the cradle and the holding ring, a circular locus is drawn on the light receiving surface of the optical measuring instrument, and the center of the circular locus and the light receiving point when the cradle is stopped The lens misalignment detector according to claim 3, wherein the decentering direction of the lens is measured from the position, and the decentering amount of the lens is measured from the diameter of the circular locus.   5. A lens centering machine comprising: the center misalignment detector according to claim 3; and centering means for aligning an optical axis of a lens placed on the cradle with a center or a rotation center of the cradle.   The centering means includes a pusher that pushes the lens toward the center of rotation of the cradle, a feed device that moves the pusher toward the axis of the cradle, and an NC controller, the NC controller Phase control means for rotating the cradle in a direction in which the decentering direction of the lens is directed to the pusher based on the measurement value of the optical measuring instrument, and the pusher is centered on the cradle based on the measurement value of the optical instrument. The lens centering machine according to claim 5, further comprising stroke control means for moving forward.

Images