JP2011107020A - Method and device for measuring spherical segment height of lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure spherical segment shape without damaging the lens surface of a subjective lens in the method and device for measuring the spherical segment height of a lens. <P>SOLUTION: The method for measuring the spherical segment height of a lens includes: a curvature radius measuring step S0 wherein the lens surface of a subjective lens is relatively moved in a direction along the optical axis to an interferometer, the interference fringe image is observed to obtain the relative movement position of the lens surface of the subjective lens in the direction along the optical axis when the condensing point is coincident with the spherical center position and the top face position of the lens surface of the subjective lens, and a distance between the relative movement positions is measured to find out the curvature radius of the lens surface of the subjective lens; a spherical segment radius measuring step S4 wherein the spherical segment radius of the lens surface of the subjective lens is measured based on the image of the lens surface of the subjective lens when the condensing point is coincided with the spherical center position of the lens surface of the subjective lens; and a calculation step S5 wherein the spherical segment height of the lens surface of the subjective lens is calculated by using the curvature radius measured in the curvature radius measuring step S0 and the spherical segment radius measured in the spherical segment radius measuring step S4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method and apparatus for measuring the height of a sphere of a lens. For example, the present invention relates to a method and apparatus for measuring the sphere height of a lens that is suitable for measuring the sphere depth and sphere height of a lens surface.

Conventionally, various shape measurement methods are used for inspecting the lens shape, but in measuring the height of a sphere, the stylus is brought into contact with the lens surface, and the stylus is moved in a direction perpendicular to the optical axis. Thus, the height of the sphere is measured by measuring the shape change in the direction along the optical axis of the lens surface.
As such a conventional lens sphere notch height measuring apparatus, Patent Document 1 discloses that a stylus is brought into contact with a sphere notch portion of a lens to be examined and the sphere nose depth is measured at a position where the value is maximum. In a sphere notch depth measuring instrument, a measurement table on which the lens to be tested is mounted, and a sphere notch depth which is disposed under the measurement table and moves the stylus in a vertical direction to measure the sphere defect depth. Measuring means, test lens holding means arranged on the measurement table for holding the test lens, XY stage for moving the test lens holding means in two horizontal directions orthogonal to each other, and the measurement table Describes a sphere defect depth measuring device including image observing means for magnifying an image of a test lens placed on the lens.

JP 2004-325387 A

  However, in the conventional lens ball height measuring method and apparatus as described above, since the measuring method using the stylus is employed as in the technique described in Patent Document 1, the stylus is There is a problem that the lens surface of the lens to be examined may be damaged by contact with the lens surface.

  The present invention has been made in view of the above-described problems, and provides a method and apparatus for measuring the sphere height of a lens that can measure the shape of the sphere without damaging the lens surface of the lens to be examined. For the purpose.

  In order to solve the above-mentioned problems, the invention according to claim 1 is a method of measuring a sphere defect height of a lens for measuring a sphere defect height of a lens surface having a sphere defect shape. A reference surface for acquiring an interference fringe image of the lens surface, splitting the coherent luminous flux and emitting one of the coherent luminous fluxes as a condensed luminous flux toward a condensing point; The lens surface to be tested that is arranged coaxially with the optical axis of the condensed light beam with respect to an interferometer that causes a reflected light beam on the test lens surface to interfere with a reflected light beam by the other of the coherent light beams on the reference surface Is relatively moved in the direction along the optical axis, and the interference fringe image acquired by the interferometer is observed, so that the focal point coincides with the spherical center position and the top position of the lens surface to be examined. Relative movement position of the lens surface in the direction along the optical axis And measuring the distance between the relative movement positions to measure the radius of curvature of the lens surface to be tested, and the focal point of the lens surface of the lens to be focused Observing the image of the lens surface to be tested when matched with the sphere, and measuring the sphere diameter of the lens surface to be measured from the image, and the radius of curvature measurement measured in the curvature radius measurement step And a sphere notch height calculating step of calculating a sphere notch height of the lens surface to be measured using a radius of curvature and the sphere notch diameter measured in the sphere notch diameter measuring step.

  According to a second aspect of the present invention, in the method of measuring the height of a sphere of the lens according to the first aspect, the step of measuring the radius of curvature includes a step in which the converging point coincides with a spherical center position of the lens surface to be examined. The interference fringe image of the test lens surface when stored is stored, and the spherical missing diameter measurement step uses the interference fringe image stored in the curvature radius measurement step as the image of the test lens surface. A method of measuring the spherical diameter of the lens surface.

According to a third aspect of the present invention, in the method for measuring a sphere defect height of a lens according to claim 1 or 2, the sphere defect diameter measurement step includes:
An image of the test lens surface is subjected to image processing, an outer diameter of the image is obtained, and converted to a dimension at the position of the test lens surface, thereby measuring the spherical missing diameter.

According to a fourth aspect of the present invention, there is provided a lens sphere defect height measuring apparatus for measuring a sphere defect height of a test lens surface having a spherical defect shape, wherein an interference fringe image of the test lens surface is obtained. A reference surface for acquisition, which splits the coherent beam and emits one of the coherent beams as a focused beam toward the condensing point, and the reflected beam from the lens surface to be tested by the collected beam And an interferometer that causes a reflected light beam reflected by the other of the coherent light beams on the reference surface to interfere with each other, and the lens surface to be measured that is disposed coaxially with the optical axis of the condensed light beam with respect to the interferometer, A movement mechanism that relatively moves in a direction along the optical axis, and a movement that acquires a relative movement position of the lens surface to be measured by the movement mechanism, calculates a difference between the relative movement positions, and measures a movement distance between the two positions. A distance measurement unit; and a reflected light beam on the lens surface to be measured in the interferometer; and An imaging unit that captures an image of the reflected light beam on the serial reference surface,
A display unit that displays an image captured by the imaging unit, and the lens surface that is arranged coaxially with the optical axis of the condensed light beam is relatively moved in a direction along the optical axis, and the condensing point Measuring the distance between the relative movement positions of the lens surface in the direction along the optical axis when the lens is coincident with the spherical center position and the top position of the lens surface. The curvature radius measurement unit that measures the radius of curvature of the test lens surface, the image of the test lens surface imaged by the imaging unit, and the test lens surface measured by the curvature radius measurement unit A spherical notch diameter measuring unit that measures a spherical missing diameter of the lens surface to be measured from a radius of curvature, and the moving distance measured by the moving distance measuring unit as the radius of curvature of the lens surface to be measured, the curvature radius and the The above-mentioned sphere defect measured by the sphere defect diameter measuring unit Wherein a structure comprising a sagittal height calculation unit for calculating the sagittal height of the lens surface, the use and.

  According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the spherical missing diameter measurement unit is stored in the storage unit that stores the interference fringe image captured by the imaging unit, and the storage unit. By calculating the outer diameter of the interference fringe image and converting the outer diameter into a distance on the test lens surface using the curvature radius of the test lens surface measured by the curvature radius measurement unit. An arithmetic processing unit for calculating the spherical diameter.

  According to a sixth aspect of the present invention, in the sphere defect height measuring device according to the fifth aspect, the arithmetic processing unit performs image processing on the interference fringe image stored in the storage unit, and The outer diameter of the interference fringe image is calculated.

  According to the method and apparatus for measuring the height of a sphere of a lens according to the present invention, a focused light beam emitted from the interferometer is measured by moving the lens surface in the direction along the optical axis and measuring the radius of curvature using an interferometer. Measure the spherical diameter of the lens surface from the image of the lens surface to be measured when the focal point of the lens coincides with the position of the spherical center of the lens surface. Since the missing height is calculated, it is possible to measure the spherical missing shape without damaging the lens surface of the test lens.

1 is a schematic front view showing a schematic configuration of a lens ball notch height measuring apparatus according to an embodiment of the present invention. 1 is a system configuration diagram showing a schematic configuration of a sphere missing height measuring device for a lens according to an embodiment of the present invention together with a schematic optical path. It is a top view which shows an example of a to-be-tested lens, and its AA sectional drawing. It is a functional block diagram which shows the function structure of the measurement control part of the ball | bowl lacking height measuring apparatus of the lens concerning embodiment of this invention. It is a flowchart which shows the process flow of the ball | bowl lacking height measuring method of the lens which concerns on embodiment of this invention. It is typical operation explanatory drawing which shows a mode that a spherical center position and a surface top position are each measured. It is a schematic diagram which shows the mode of the display screen in a curvature radius measurement process. It is a schematic diagram which shows an example of the image process in a spherical missing diameter measurement process. It is a typical optical path diagram for demonstrating the relationship between the length on an image sensor, and the length on a to-be-tested lens. It is a typical system block diagram which shows schematic structure of the ball | bowl lacking height measuring apparatus of the lens which concerns on the modification of embodiment of this invention.

  Hereinafter, a method and apparatus for measuring the height of a sphere of a lens according to an embodiment of the present invention will be described with reference to the accompanying drawings. In all the drawings, even if the embodiments are different, the same or corresponding members are denoted by the same reference numerals, and common description is omitted.

A lens ball height measuring apparatus according to an embodiment of the present invention will be described.
FIG. 1 is a schematic front view showing a schematic configuration of a lens ball height measuring apparatus according to an embodiment of the present invention. FIG. 2 is a system configuration diagram showing a schematic configuration of the lens sphere height measuring device according to the embodiment of the present invention together with a schematic optical path. FIG. 3A is a plan view showing an example of a test lens. FIG.3 (b) is AA sectional drawing in Fig.3 (a). FIG. 4 is a functional block diagram showing a functional configuration of the measurement control unit of the lens ball gap height measuring device according to the embodiment of the present invention.

  As shown in FIGS. 1 and 2, the sphere defect height measuring apparatus 50 according to the present embodiment uses the sphere defect height measurement method of the lens according to the present embodiment to test the test lens 4 having a sphere defect shape. It is an apparatus for measuring the height of a sphere of the lens surface S.

First, the test lens 4 for measuring the sphere defect depth by the sphere defect height measuring device 50 will be described.
The test lens 4 is not particularly limited as long as it is a lens having a test lens surface S having a spherical shape, and may be a concave lens or a convex lens. Hereinafter, as an example, a description will be given of an example of a plano-concave lens as shown in FIGS.
The test lens 4 has a first surface 4a that is a concave spherical surface having a radius of curvature R at the center of one surface in the thickness direction, and a second surface 4b that is a flat surface on the other surface in the thickness direction. Is formed. Hereinafter, the center of curvature of the first surface 4a is referred to as a sphere center O (sphere center position).
The outer shape of the test lens 4 in the thickness direction is a thickness H, and one surface in the thickness direction on which the first surface 4a is formed is parallel to the second surface 4b on the outer peripheral side of the first surface 4a. A mounting surface 4c for positioning the lens 4 to be tested in the optical axis direction is formed.
That is, the first surface 4a has a sphere shape in which a sphere having a radius of curvature R is cut out by the attachment surface 4c, and is a lens surface S having a sphere shape.
In the present specification, the maximum outer diameter of the first surface 4a having a spherical shape is referred to as a spherical shape. The spherical missing diameter D of the first surface 4a is equal to the diameter of the lens surface outline 4e, which is the intersection line between the first surface 4a and the mounting surface 4c.
Further, the top surface Q (surface top position) of the first surface 4a is designed so as to be positioned at the height h of the sphere from the mounting surface 4c (where h <H). For this reason, the lens surface space | interval of the 1st surface 4a and the 2nd surface 4b is Hh.
The sphere notch height h may be referred to as a sphere notch depth because the first surface 4a has a concave sphere shape. However, in this specification, the sphere nose height is a sphere regardless of whether the sphere shape is concave or convex. This is called a missing height.
The lens side 4d of the lens 4 is made cylindrical surface of diameter D ₀ which is formed on the optical axis coaxial with the first surface 4a, it is used as a reference surface for positioning the radial of the lens 4 .

  As shown in FIGS. 1 and 2, the schematic configuration of the sphere missing height measuring apparatus 50 includes a gantry 16, an interferometer 30 (see FIG. 2), a vertical movement mechanism 13 (movement mechanism), an XY movement stage 15, and a length measuring device. 14 (movement distance measurement unit), a measurement control unit 8, a monitor 23 (display unit), and an operation unit 25.

  The gantry 16 includes an upper base 16a disposed above, a lower base 16b disposed below the upper base 16a, and a column portion that supports the upper base 16a and the lower base 16b at a constant interval. 16c.

The interferometer 30 has a reference surface for acquiring an interference fringe image of the lens surface S to be measured, divides the coherent light beam, and emits one of the coherent light beams as a condensed light beam directed toward the condensing point. In this embodiment, as an example, a Fizeau interferometer is used to cause interference between the reflected light beam on the lens surface S to be measured and the reflected light beam on the other side of the coherent light beam on the reference surface. ing. In the Fizeau interferometer, the reference surface also serves as a light beam dividing surface for dividing the coherent light beam.
As shown in FIG. 2, the schematic configuration of the interferometer 30 includes a laser light source 1, a collimator lens 2, a beam splitter 11, a reference lens 5, a condenser lens 10, and an imaging element 9 (imaging unit). Among these, each member except for the laser light source 1 is an inside of a substantially cylindrical interferometer main body 20 (see FIG. 1) extending in the vertical direction and penetrating through the center of the upper base 16a of the gantry 16. Are held in a state of being positioned with respect to each other.
That is, in the interferometer body 20, the reference lens 5, the beam splitter 11, the condenser lens 10, and the image sensor 9 are arranged in this order from the lower side to the upper side along the vertical axis. The collimator lens 2 is disposed on the side of the beam splitter 11 and in the vicinity of an opening (not shown) provided on the side surface of the interferometer body 20.
Although not particularly illustrated, a shutter for stopping the emission of the condensed light beam from the interferometer 30 by an operator's operation is provided on the optical path in the laser light source 1 or the interferometer main body 20.

The laser light source 1 is a light source for generating the laser light L ₀ that is a coherent light beam, and an appropriate light source that is employed in an interferometer can be employed. In the present embodiment, a laser oscillator composed of a He—Ne laser disposed outside the interferometer body 20 is employed.
One end of an optical fiber 17 is connected to the laser light source 1, and the laser light L ₀ transmitted through the optical fiber 17 can be emitted from the other end of the optical fiber 17 as a divergent light beam.
The other end of the optical fiber 17 is connected to the optical fiber connector 3 provided on the side surface of the interferometer body 20.

The collimator lens 2 condenses the laser light L ₀ emitted from the fiber end face on the other end side of the optical fiber 17 connected to the optical fiber connector 3 to form the laser light L ₁ that is a parallel light flux, and the laser light. This is an optical element for causing L ₁ to enter the beam splitter 11.
Beam splitter 11 is configured to reflect the laser beam L ₁ emitted from the collimator lens 2 vertically downward, an optical path branching element which transmits the laser beam vertically upward incident from the vertical lower side.

The reference lens 5 is a Fizeau lens for constituting a Fizeau interferometer, and transmits a part of the laser beam L ₁ , which is a parallel light beam reflected by the beam splitter 11, as a laser beam L _2. The light is condensed on a light condensing point P outside.
Reference lens 5, a final lens surface where the laser beam L ₂ is emitted towards the converging point P, comprises a reference surface 5a made of a high-precision spherical spherical center at the focal point P is matched.
In the present embodiment, the optical axis of the reference lens 5 is arranged along the vertical axis. For this reason, the optical axis C defined by the axial principal ray of the optical path of the laser light from the center of the end face of the other end of the optical fiber 17 to the condensing point P is the optical axis of the laser light L ₂ that is a focused light beam. In this embodiment, the vertical axis passing through the center of the reference lens 5 between the beam splitter 11 and the condensing point P coincides with the vertical axis.
Thus the laser beam L ₂ passes through the focal point P, directed vertically downward diverges and is irradiated to the sample lens 4. In the present embodiment, in order to observe the spherical diameter of the test lens surface S, interference fringes on the entire surface of the test lens surface S can be acquired. That is, the NA (numerical aperture) of the illumination optical system composed of the optical fiber 17, the collimator lens 2, and the reference lens 5 is adjusted to a predetermined value according to the spherical diameter of the lens 4 to be examined, the laser beam L ₂ is to be irradiated to a wider range than the sample lens surface S when the sample lens surface S are aligned as the spherical center O of the subject lens surface S is equal to P.
Therefore, as the measured surface reflection light beam L ₃ in which the reflected light is a reflected light beam at the sample lens surface S of the laser beam L ₂ irradiated to the subject lens 4 the first surface 4a, again a reference surface 5a Incident light is collected by the reference lens 5 and emitted toward the beam splitter 11 side.
Further, the laser light L ₁ reflected by the reference surface 5a is an optical path with reverse as the reference surface reflected light beam L _{4 (the} other by the reflected light beam of the coherent light beam at the reference plane), is emitted to the beam splitter 11 side The

The condensing lens 10 is a lens that condenses the test surface reflected light beam L ₃ and the reference surface reflected light beam L ₄ that pass through the beam splitter 11 and travel vertically upward, and projects the collected light onto the image sensor 9.
The image sensor 9 captures a light image by the light beam projected by the condenser lens 10 and sends it to the measurement control unit 8. As the image sensor 9, for example, an image sensor such as a CCD or a CMOS element can be employed.
Therefore, when an interference fringe image is formed by the test surface reflected light beam L ₃ and the reference surface reflected light beam L ₄ , an interference fringe image is captured by the image sensor 9 and sent to the measurement control unit 8. The

According to the interferometer 30 having such a configuration, when the test lens 4 is arranged on the lower side of the interferometer 30 with the first surface 4a facing upward as the test lens surface S, the sphere of the first surface 4a a position where the heart O coincides with the focal point P, at two positions of a position surface apex Q of the first surface 4a coincides with the focal point P, is the subject surface reflected light beam L ₃ on the first surface 4a It will go back along the incident optical path.
At these two positions, the optical path difference from the reference surface reflected light beam L ₄ reflected by the reference surface 5a is only an error in the spherical shape of the first surface 4a with respect to the reference surface 5a, so that the test surface reflected light beam L ₃ and fringe number of interference fringes by the reference surface reflection light beam L ₄ is minimal interference fringe image is formed.

The vertical movement mechanism 13 is a uniaxial movement mechanism whose lower end portion is supported so as to be movable in the vertical direction with respect to the lower base 16 b of the gantry 16, and an XY movement stage 15 is provided at the upper end portion.
As the configuration of the vertical movement mechanism 13, for example, a configuration such as a single-axis stage that moves in a single-axis direction by a screw feed mechanism, a linear actuator, or a linear motor can be suitably employed.
The vertical movement mechanism 13 may be driven under the control of the measurement control unit 8, but in the present embodiment, as an example, the vertical movement mechanism 13 is driven by a dedicated drive operation unit (not shown) connected to the vertical movement mechanism 13. I am doing so.

XY moving stage 15 is a two-axis moving stage for performing optical axis adjustment to align the optical axis of the lens 4 on the optical axis C of the laser beam L _2, by placing a sample lens 4 on the top surface The position of the test lens 4 can be adjusted in the horizontal plane.
An appropriate holding shape (not shown) is provided on the uppermost surface of the XY moving stage 15 in order to position and hold the test lens 4 in the direction along the optical axis and in the radial direction perpendicular to the optical axis. . For example, in the present embodiment, corresponding to the fact that the test lens 4 is a plano-concave lens, a placement portion on which the second surface 4b is placed, and a radial positioning portion that contacts and positions the lens side surface 4d Is provided.

As a specific configuration of the XY moving stage 15, a biaxial moving stage in which the uniaxial moving stage is combined so that the moving directions thereof are orthogonal to each other can be adopted.
Further, the movable range of the XY moving stage 15 is moved in a range that can adjust the amount of positional displacement between the optical axis C of the optical axis and the laser beam L ₂ of the lens 4 placed on an XY moving stage 15 I can do it.
In this embodiment, in order to measure not only the radius of curvature of the first surface 4a but also the sphere diameter, if the lens surface outline 4e is inclined with respect to a plane orthogonal to the optical axis C, the sphere diameter will be reduced. Measurement error. For this reason, the mounting portion of the XY moving stage 15 is adjusted in advance so as to be orthogonal to the optical axis C. Note that a placement unit may be provided on the XY moving stage 15 via an inclination stage so that the inclination can be adjusted as necessary.

The length measuring device 14 is for measuring the distance in the direction along the optical axis C between the lens 4 to be tested placed on the XY moving stage 15 and the condensing point P of the interferometer 30.
In the present embodiment, in order to measure the vertical movement position of the upper end portion of the vertical movement mechanism 13 with respect to the lower base 16b, the vertical movement mechanism 13 is installed in parallel with the vertical movement mechanism 13.
As the configuration of the length measuring device 14, for example, a laser length measuring device or a length measuring device using a linear encoder can be suitably employed.
The length measuring device 14 is electrically connected to the measurement control unit 8, and can send information on the movement position of the vertical movement mechanism 13 to the measurement control unit 8.

The measurement control unit 8 controls the measurement operation of the ball defect height measuring device 50 and is electrically connected to the image sensor 9 and the length measuring device 14 as shown in FIG. Further, the operation unit 25 that performs operation input for controlling the measurement operation and the monitor 23 that displays an image captured by the image sensor 9 and an operation screen for performing operation input on the display screen 23a are electrically connected. Has been.
The functional configuration of the measurement control unit 8 includes an image acquisition unit 80, an apparatus control unit 81, an image processing unit 85, a calculation unit 82, a storage unit 83, and a display control unit 84, as shown in FIG.

  The image acquisition unit 80 acquires a video signal transmitted from the image sensor 9 under the control of the device control unit 81. The video signal acquired by the image acquisition unit 80 is subjected to noise removal, luminance correction, and the like as necessary, and then converted into two-dimensional image data for each video frame, which is transmitted to the device control unit 81 and the display control unit 84. Sent out.

The device control unit 81 analyzes the operation input input from the operation unit 25 and performs overall control of the measurement of the sphere height according to the operation input.
Examples of the control performed by the apparatus control unit 81 include control for storing the two-dimensional image data transmitted from the image acquisition unit 80 in the storage unit 83, and various information such as the connected operation unit 25 and the length measuring device 14. The image processing unit 85 obtains the acquired information and stores the acquired information in the storage unit 83, and calculates a radius of curvature, a spherical missing diameter, or a spherical missing height based on the information stored in the storage unit 83. And control for starting processing by the calculation unit 82.
Moreover, as information acquired from the length measuring device 14, the positional information of the up-and-down moving mechanism 13 can be mentioned. This position information can be acquired at a timing according to an operation input from the operation unit 25.
Further, the device control unit 81 generates display data for displaying on the monitor 23 an operation screen for performing an operation input by the operation unit 25, various calculation results calculated by the calculation unit 82, and the like. Control to send to 84 is also performed.

The image processing unit 85 reads the two-dimensional image data stored in the storage unit 83 based on the control signal from the device control unit 81, and obtains the outer diameter of the interference fringe image projected on the image sensor 9, for example. Image processing is performed, and information on the obtained outer diameter is sent to the calculation unit 82.
The calculation unit 82 calculates the curvature radius of the lens surface S to be measured based on the information stored in the storage unit 83 based on the control signal from the apparatus control unit 81, and the curvature radius and the storage unit 83 store the curvature radius. Based on the stored information and the outer diameter of the interference fringe image obtained by the image processing unit 85, an operation for calculating the spherical missing diameter and the spherical missing height is performed, and these calculation results are sent to the apparatus control unit 81. To be sent.
The storage unit 83 is for storing information sent from the device control unit 81, the calculation result of the calculation unit 82, and the like.
The display control unit 84 appropriately switches or superimposes the two-dimensional image data transmitted from the image acquisition unit 80 and the display data transmitted from the device control unit 81, and then, for example, a video signal such as an NTSC signal. Is converted to and sent to the monitor 23.

In this embodiment, a computer including a CPU, a memory, an input / output interface, and an external storage device is employed as the device configuration of the measurement control unit 8. And the control function and arithmetic function which were demonstrated above are implement | achieved by running the program corresponding to each.
The device configuration of the operation unit 25 can employ, for example, a keyboard or a mouse.

Next, a method for measuring the sphere height of the lens according to the present embodiment, which is performed using the sphere height measurement apparatus 50, will be described together with the operation of the sphere height measurement apparatus 50.
FIG. 5 is a flowchart showing a process flow of the method for measuring the height of a sphere of a lens according to an embodiment of the present invention. FIGS. 6A and 6B are schematic operation explanatory views showing how the ball center position and the surface top position are respectively measured. FIGS. 7A and 7B are schematic views showing the state of the display screen in the curvature radius measurement step. FIGS. 8A and 8B are schematic views showing an example of image processing in the ball missing diameter measuring step. FIG. 9 is a schematic optical path diagram for explaining the relationship between the length on the image sensor and the length on the lens to be examined.

  As shown in FIG. 5, the method of measuring the height of the sphere of the lens according to the present embodiment includes a sphere center position measurement step S1, a surface apex position measurement step S2, a curvature radius calculation step S3, a sphere nose diameter measurement step S4, and a sphere. A missing height calculating step S5 is provided.

Spherical center position measurement step S1 is for the interferometer 30, the optical axis C and the sample lens surface S disposed coaxially are relatively moved in the direction along the optical axis C, the laser beam L ₂ converging point This is a step of acquiring the relative movement position between the interferometer 30 and the lens surface S in a positional relationship in which P coincides with the position of the sphere center O of the lens surface S.
First, as a measurement preparation, the measurer moves the drive operation unit of the vertical movement mechanism 13 so that the spherical center O of the first surface 4a arranged on the XY movement stage 15 is substantially the same height as the focal point P. Operate to adjust the height of the vertical movement mechanism 13. In the present embodiment, as shown in FIG. 6 (a), adjusted to the height of the target height h _1.
At this time, in the present embodiment, the target height h ₁ is determined by the device control unit 81 of the measurement control unit 8 by using the design value of the radius of curvature of the first surface 4a (the lens surface S to be measured) and the spherical notch height measuring device. It is calculated in advance from the 50 dimensions and is displayed on the monitor 23 via the display control unit 84. The height of the vertical movement mechanism 13 is sent to the device control unit 81 sequentially from the measured value by the length measuring device 14, and is displayed on the monitor 23 by the device control unit 81 via the display control unit 84.
Therefore, measuring person, while viewing the monitor 23, may operate the drive operation portion as measured values of the measurement unit 14 becomes the target height h _1.
Further, the XY moving stage 15 has a biaxial position set to a neutral position, and the optical axis of the first surface 4a is in a positional relationship that approximately coincides with the optical axis C.

Next, the measurer performs the operation of opening the shutter (not shown), in a state where the laser beam L ₂ is emitted from the interferometer main body 20, an operation input for starting the sphere center position measurement process S1 from the operation unit 25 I do.
As shown in FIG. 2, the laser light L ₀ generated by the laser light source 1 and propagated through the optical fiber 17 and emitted from the fiber end surface of the optical fiber 17 enters the interferometer body 20 and collimator lens 2. is focused as a laser beam L ₁ is a parallel light beam by.
The laser light L ₁ enters the beam splitter 11, is reflected downward by the beam splitter 11, travels on the optical axis C, enters the reference lens 5, and is collected by the reference lens 5.
Backward when the laser beam L ₁ reaches the reference surface 5a, the laser beam L ₂ is emitted vertically downward as converging light beam the reference surface 5a is transmitted through, reflected by the reference surface 5a to the optical path of the laser beam L ₁ It is split into a reference surface reflection light beam L ₄ of.
The reference surface reflected light beam L ₄ is emitted as a parallel light beam above the reference lens 5, travels on the optical axis C, passes through the beam splitters 11, 12, and is collected by the condensing lens 10, and then the image sensor 9. Reach up.

On the other hand, the laser beam L ₂ diverges after being condensed at the focal point P, is irradiated onto the surface of the lens 4 that includes a first surface 4a. A part of the laser light L ₂ is reflected as a test surface reflected light beam L _{3 on} the first surface 4 a, travels substantially backward in the optical path of the laser light L ₂ , and reenters the reference surface 5 a, so that it is a substantially parallel light beam. Is emitted above the reference lens 5. For this reason, the test surface reflected light beam L ₃ passes through the beam splitters 11 and 12, and is collected by the condensing lens 10 and reaches the image pickup device 9, similarly to the reference surface reflected light beam L ₄ .
Since the test surface reflected light beam L ₃ and the reference surface reflected light beam L ₄ have an optical path difference corresponding to the reciprocal optical path between the reference surface 5a and the first surface 4a, interference occurs according to the optical path difference on the reference surface 5a. Stripes are formed. The interference fringe image is picked up by the image pickup device 9 and sent to the image acquisition unit 80 of the measurement control unit 8 as a video signal.

On the other hand, the outer optical path different from the test surface reflection light beam L ₃ and the reference surface reflection light beam L ₄ as reflected light of mounting the laser light is irradiated to the surface 4c L ₂ is re-entering the reference lens 5 of the first face 4a Therefore, it hardly reaches the image pickup device 9 like other measurement unnecessary light.

  The image acquisition unit 80 performs noise removal, luminance correction, and the like on the acquired video signal as necessary, converts the video signal into two-dimensional image data for each video frame, and sends the data to the display control unit 84. Then, it is converted into a video signal to be displayed on the monitor 23 by the display control unit 84 and displayed on the display screen 23a.

FIG. 7A shows an example of an image displayed on the display screen 23a.
Since only the test surface reflected light beam L ₃ and the reference surface reflected light beam L ₄ reach the imaging device 9, the display screen 23 a is caused by the test surface reflected light beam L ₃ and the reference surface reflected light beam L ₄ . interference fringe image I ₁ is displayed outside of the interference fringe image I ₁ has a dark portion.
A region F indicated by a two-dot chain line in FIG. 7A indicates a maximum region where an interference fringe image can be displayed for convenience of reference. The size of the region F is determined by the NA of the optical system composed of the reference lens 5 and the condenser lens 10.
Actually, since the reference surface reflected light beam L ₄ reaches the range of the region F, the range of the region F outside the interference fringe image I ₁ is relatively bright compared to the outside of the region F. , for sufficiently low intensity than the high luminance portion of the interference fringe image I _1, not distinguished in the illustrated. Alternatively, by adjusting the contrast of the monitor 23, the range outside the region F of the interference fringe image I ₁ may be allowed to appear as a dark portion.
Outline 4E ₁ of the interference fringe image I ₁ is circular because it corresponds to the lens surface contour 4e of the first face 4a.
Interference fringe image I ₁ is in a state not subjected to positional adjustment of the first face 4a, since a position the spherical center O is shifted from the focal point P, as shown schematically in FIG. 7 (a), The number of interference fringes is extremely large. Alternatively, in some cases, the image cannot be discriminated from stripes.

On the other hand, by moving the first surface 4a, in the state where focusing and point P and the spherical center O is matched, the amount of deviation of the wavefront of the test surface reflection light beam L ₃ with respect to the reference surface 5a is the reference surface 5a and the first because only the deviation amount based on the shape error of the surface 4a becomes no interference fringe number is remarkably reduced, for example, an interference fringe image I ₀ as schematically shown in FIG. 7 (b) is displayed. Outline 4E interference fringe image I _{0 0,} as in the case of the interference fringe image I _1, a circular corresponding to the lens surface contour 4e.

Therefore, measuring person, while viewing the image on the display screen 23a, and drives the vertical movement mechanism 13, is finely moved in the direction along the first surface 4a to the optical axis C, fringe number of interference fringe image I ₁ is minimum Adjust to the height to be. At this time, the XY moving stage 15 is driven to move the first surface 4a in the direction orthogonal to the optical axis C, and it is confirmed whether the number of stripes is further reduced. When the number of stripes is further reduced, the vertical movement mechanism 13 is slightly moved again in this state. These operations are repeated to minimize the number of interference fringe images on the display screen 23a. Thus, the spherical center O of the first surface 4a is in a state of being matched at the focal point P, the interference fringe image I ₀ as shown in FIG. 7 (b) is observed.

When such position adjustment is completed, the measurer inputs from the operation unit 25 that the adjustment of the ball center position has been completed.
Thereby, the apparatus control unit 81 of the measurement control unit 8 acquires the height information of the vertical movement mechanism 13 from the length measuring device 14, acquires the interference fringe image I ₀ from the image acquisition unit 80, and stores each of them. Store in the unit 83. This height is defined as a height H ₁ (see FIG. 6A).
The height H ₁ is the focal point P of when matched to the position of the spherical center O of the first face 4a, interferometer 30 lower based on the direction of the relative movement position along the optical axis C of the first surface 4a against It is measured from the reference position on the table 16b.
The ball center position measurement step S1 is thus completed.

Next, a surface top position measurement step S2 is performed.
In this step, with respect to the interferometer 30, in a direction along the first surface 4a which is arranged on the optical axis C coaxial to the optical axis C is relatively moved, the focal point P of the laser beam L ₂ is the first surface This is a step of acquiring a relative movement position that coincides with the surface top Q of 4a.
The measurer performs an operation input for starting the surface top position measurement step S2 from the operation unit 25.
Next, the driving operation unit of the vertical movement mechanism 13 is operated while viewing the display screen 23a, and the vertical movement mechanism 13 is moved in the direction in which the surface top Q approaches the condensing point P. As a result, an image with a high number of stripes is displayed on the display screen 23a and the number of stripes cannot be determined. However, when the top Q approaches the condensing point P, an interference fringe image with a small number of stripes is displayed.
At this time, as shown in FIG. 6 (b), the test surface reflection light beam L ₃ is to be reflected by the first surface 4a in the vicinity of the focal point P, and then re-enters the reference surface 5a, substantially parallel As a light beam, the light is emitted above the reference lens 5, passes through the beam splitter 11, and is collected by the condensing lens 10, similarly to the reference surface reflected light beam L _4, and then reaches the image sensor 9.
Once the collector and point P and a surface apex Q matches are called cat's eye position, the wavefront of the test surface reflection light beam L ₃ reflected is condensed in dots in surface apex Q is the reference surface 5a Since there is almost no deviation from the shape, the number of interference fringes is substantially zero.
Therefore, the measurer minimizes the number of fringes by adjusting the positions of the vertical movement mechanism 13 and the XY movement stage 15 while viewing the display screen 23a as in the ball center position measurement step S1.

When this position adjustment is completed, the measurer inputs from the operation unit 25 that the adjustment of the top position has been completed. As a result, the device control unit 81 of the measurement control unit 8 acquires the height information of the vertical movement mechanism 13 from the length measuring device 14 and stores the information on the center position stored in the center position measurement step S1 in the storage unit 83. the height H ₁ distinguished to be stored with. This height is defined as a height H ₂ (see FIG. 6B).
The height H ₂ is when the converging point P is matched to the position of the surface apex Q of the first surface 4a, the direction of the relative movement position along the optical axis C of the first surface 4a for the interferometer 30, the lower It is measured from the base 16b.
The surface top position measuring step S2 is thus completed.

Next, a curvature radius calculation step S3 is performed.
In this step, the radius of curvature R of the first surface 4a is measured by measuring the distance in the direction along the optical axis C between the two positions of the heights H ₁ and H ₂ stored in the storage unit 83. It is.
When the height H ₂ is stored, the device control unit 81 sends a control signal to the calculation unit 82 and causes the calculation unit 82 to calculate the curvature radius R. For this reason, the measurement control part 8 comprises the curvature radius measurement part.
The calculation unit 82 reads the heights H ₁ and H ₂ from the storage unit 83, calculates the curvature radius R from the following equation (1), sends it to the device control unit 81, and stores it in the storage unit 83.

R = | H ₁ −H ₂ | (1)

When the curvature radius R is sent from the calculation unit 82, the device control unit 81 reads the heights H ₁ and H ₂ from the storage unit 83, and displays the measurement results together with the curvature radius R calculated by the calculation unit 82. Data is generated, sent to the display control unit 84, and displayed on the display screen 23a.
The curvature radius calculation step S3 is thus completed.

In such a spherical center position measurement step S1, surface top position measurement step S2, and curvature radius calculation step S3, the test lens surface S arranged coaxially with the optical axis C with respect to the interferometer 30 is placed on the optical axis C. The optical axis C when the focal point P coincides with the spherical center O and the surface apex Q of the lens surface S to be measured by observing the interference fringe image acquired by the interferometer 30 with relative movement in the direction along Are obtained as heights H ₁ and H ₂ , respectively, and by measuring the distance between these relative movement positions, the radius of curvature R of the test lens surface S is obtained. The radius of curvature measurement step S0 for measuring is configured.

Next, a ball missing diameter measuring step S4 is performed.
In this step, an image of the test lens surface S when the condensing point P coincides with the sphere center O of the test lens surface S is observed, and the spherical missing diameter D of the test lens surface S is determined from this image. It is a process of measuring.
In the present embodiment, as the image of the first surface 4a, using an interference fringe image I ₀ obtained when the spherical center O is matched to the focal point P at the sphere center position measurement step S1, the interference fringe image I ₀ the diameter of the contour lines 4E _0, measuring the Tamaketsu径D by converting the actual dimensions of the lens surface contour 4e.
When the curvature radius calculation step S <b> 3 is completed, the apparatus control unit 81 sends a control signal for starting the measurement of the sphere diameter to the image processing unit 85.
Thus, the image processing unit 85 from the storage unit 83 reads out the interference fringe image I _0, subjected to binarization processing to two-dimensional image data of the interference fringe image I _0.
The threshold value for the binarization process becomes 0 at a luminance equal to or lower than the low luminance portion of the region F outside the interference fringe image I ₀ , and is strengthened by the interference between the test surface reflected light beam L ₃ and the reference surface reflected light beam L ₄ . It is set so that it does not become 0 in the high luminance part.
Thus, the binary image J ₁ as shown in FIG. 8 (a) is obtained. Here, for the sake of easy viewing, the high luminance data is shown in black (the same applies to FIG. 8B).
Next, the image processing unit 85, as well as performing an edge extraction process on the binary image J _1, performs image processing for removing the image component that becomes the edge of the interference fringes corresponding to the outline 4E ₀ of the interference fringe image I0 only outline _{J 2} of the binary image _{J 1} is extracted to, to calculate the diameter _{d 0} of the outline _{J 2.}
Here, the method for calculating the diameter outline J ₂ can adopt an appropriate algorithm. For example, the diameter d ₀ can be calculated by calculating an approximate circle of the outline J ₂ by a known circle fitting calculation process or the like. The diameter d ₀ is calculated as an actual dimension on the image sensor 9.
The calculated diameter d ₀ is sent from the image processing unit 85 to the calculation unit 82.

Next, the arithmetic unit 82, converts the diameter d ₀ to the actual dimensions of the lens surface contours 4e at the position of the first surface 4a.
As shown in FIG. 9, the diameter d _F of the region F indicates the range in which the reflected light beam L _F reaches the image sensor 9 when the spherical surface having the curvature radius R is arranged in the range of the opening angle 2θ _F. . For this reason, when the light flux diameters of the reflected light beam L _F and the test surface reflected light beam L ₃ between the reference lens 5 and the condensing lens 10 which are parallel light beams are expressed as diameters W _F and W ₀ , respectively, 2) to (6) hold.
Incidentally, the beam diameter of the reflected light beam L _F, in the present embodiment, equal to the beam diameter of the reference surface reflected light beam L _4.

d ₀ / d _F = W ₀ / W _F (2)
W _F = 2 · f · tan θ _F (3)
W ₀ = 2 · f · tan θ ₀ (4)
D _F = 2 · R · sin θ _F (5)
D = 2 · R · sin θ ₀ (6)

Here, R is the curvature radius of the first surface 4a calculated in the curvature radius calculation step S3, and f is an optical system (in this embodiment, the reference lens 5) that converts the incident light beam to the reference lens 5 into a parallel light beam. The focal length.
When the above formulas (2) to (6) are used, the formula (6) is expressed as the following formula (7).

Therefore, the aperture half angle θ _F determined by the NA of the optical system that forms the laser beam L ₂ , and the diameter d _{F of the} region F determined by the optical characteristics of the reference lens 5 and the condensing lens 10 and the arrangement position of the image sensor 9 are stored. An operation for storing in advance in the unit 83 and substituting these values, the diameter d ₀ sent from the image processing unit 85, and the value of the curvature radius R calculated in the curvature radius calculation step S3 into the equation (7). The spherical diameter D is calculated by the calculation unit 82.
For this reason, the memory | storage part 83, the image process part 85, and the calculating part 82 comprise the spherical missing diameter measurement part. Further, the image processing unit 85 and the calculation unit 82 calculate the outer diameter of the interference fringe image I ₀ stored in the storage unit 83, and the curvature of the lens surface S to be measured, which is measured by the curvature radius measurement unit. An arithmetic processing unit that calculates the spherical missing diameter D by converting the radius R into a distance on the lens surface S to be measured is configured.
Thus, the ball missing diameter measurement step S4 is completed.

  Next, the sphere notch height calculation step S5 is a step in which the calculation unit 82 calculates the sphere nose height h from the curvature radius R and the sphere nose diameter D by the following equation (8) based on the three-square theorem. . For this reason, the calculating part 82 comprises the ball lacking height calculation part.

h = R−√ {R ² − (D / 2) ² } (8)

The calculated ball missing height h is sent to the apparatus control unit 81.
In the apparatus control unit 81, display data for displaying the sphere height h as a measurement result is generated, sent to the display control unit 84, and displayed on the display screen 23a.
Thus, the ball missing height calculating step S5 is completed.

According to the sphere notch height measuring method using the sphere nose height measuring device 50 of this embodiment, the curvature radius R is measured using the interferometer 30 by moving the lens surface S to be tested in the direction along the optical axis C. and, the sample lens surface from the interference fringe image I ₀ of the lens surface S when the converging point P of laser light L ₂ emitted from the interferometer 30 is matched to the spherical center O of the lens surface S In order to measure the spherical missing diameter D of S and calculate the spherical missing height h using the radius of curvature R and the spherical missing diameter D, the first surface 4a which is the measured lens surface S of the measured lens 4 is formed. Sphere shape can be measured without damaging.

  Further, according to the sphere missing height measuring apparatus 50 of the present embodiment, since the image for measuring the sphere missing diameter D is an interference fringe image, an image of the first surface 4a is acquired to obtain the sphere missing diameter D. Therefore, it is not necessary to add an illumination light source for imaging, an imaging means for imaging an image of the lens surface outline 4e, and the like, and it is possible to perform a curvature radius measurement and a sphere notch depth measurement with a simple configuration.

[Modification]
Next, a description will be given of a lens notch height measuring apparatus according to a modification of the embodiment of the present invention.
FIG. 10 is a schematic system configuration diagram showing a schematic configuration of a lens notch height measuring device according to a modification of the embodiment of the present invention.

  As shown in FIG. 10, a sphere defect height measuring device 51 according to the present modification includes a Twiman Green interferometer in the interferometer body 20 instead of the interferometer 30 which is the Fizeau interferometer of the above embodiment. A certain interferometer 40 is provided. Note that FIG. 10 is a schematic diagram illustrating a schematic configuration, and thus the optical fiber 17, the gantry 16, and the like are not illustrated.

The interferometer 40 includes the collimator lens 2, the condensing lens 10, and the image sensor 9, similarly to the interferometer 30 of the above embodiment. Instead of the beam splitter 11 and the reference lens 5, the beam splitter 34 and the reference spherical mirror 36 are provided. , And condenser lenses 33 and 35 and a shutter 37 are added. Further, a measurement control unit 8A is provided instead of the measurement control unit 8.
Here, on the optical axis of the laser beam L ₁ emitted from the collimator lens 2, the beam splitter 34, a condenser lens 35, the reference spherical mirror 36 are disposed in this order.

The beam splitter 34 reflects a part of the laser beam L ₁ emitted from the collimator lens 2 vertically downward as a laser beam L ₁₂ and transmits the other laser beam L _{1 to} the condensing lens 35. an optical path branching element for dividing the L _10. The beam splitter 34 is adapted to transmit a laser beam incident from the vertically lower side vertically upward, to reflect the backward laser beam vertically upward the optical path of the laser beam L _10.

Condensing lens 35, after converging the laser light L _10, a lens to be incident on the reference spherical mirror 36 as a divergent light flux.
The reference spherical mirror 36 includes a reference surface 36a composed of a high-precision spherical mirror surface for constituting a Twyman Green interferometer, and the center of curvature O ′ coincides with the condensing point P ′ of the condensing lens 35. Are arranged as follows. Therefore, the laser beam L ₁₀ is reflected by the reference surface 36a is an optical path with reverse as the reference surface reflected light beam L _{11 (the} other by the reflected light beam of the coherent light beam at the reference plane), re the condensing lens 35 Incident light is converted into a parallel light beam and emitted to the beam splitter 34 side.

Further, between the beam splitter 34 and the condenser lens 35, and moved in the optical path of the laser beam L _10, a shutter 37 is provided for shielding or passing the laser beam L _10.
The shutter 37 may be configured to be manually switched between advance and retreat, but in the present modification, an appropriate actuator that performs advance and retreat driving by control via the measurement control unit 8A is provided.

The condensing lens 33 condenses the laser light L ₁₂ reflected by the beam splitter 34 and traveling vertically downward along the optical axis C at the same condensing point P as in the above embodiment outside the interferometer body 20. It is a lens to be made.
The NA of the condenser lens 33 is set in the same manner as the NA of the reference lens 5 according to the size and the radius of curvature of the test lens surface S of the test lens 4.

  The measurement control unit 8A is electrically connected to the shutter 37, and in addition to the functional configuration of the measurement control unit 8 of the above embodiment, the device control unit 81 has a function of controlling the opening and closing of the shutter 37. .

According to such a configuration, in a state where the shutter 37 is opened, an interference fringe image can be formed in a state where the ball center O of the first surface 4a is substantially coincident with the condensing point P by the interferometer 40. .
That is, the laser light L ₀ emitted from the laser light source 1 enters the interferometer main body 20 and is collected by the collimator lens 2 as the laser light L ₁ that is a parallel light beam.
The laser beam L ₁ is incident on the beam splitter 34, and a part of the laser beam L ₁ is reflected downward by the beam splitter 34 as the laser beam L ₁₂ , travels on the optical axis C, enters the condenser lens 33, and is collected. The light is condensed at the condensing point P by the optical lens 33.
On the other hand, in addition to the laser beam L ₁ , the laser beam L ₁₀ passes through the beam splitter 34 and travels straight, enters the condenser lens 35, and is collected by the condenser lens 35 at the condensing point P ′. Then, it enters the reference surface 36a of the reference spherical mirror 36 as a divergent light beam.
The laser beam L _10, once reflected by the reference surface 5a, as a reference surface reflected light beam L _4, and reversing the optical path of the laser beam L _10, the beam splitter is parallel light flux is condensed by the condensing lens 35 34 is reached. A part of the light is reflected by the beam splitter 34 and condensed by the condenser lens 10, and then reaches the image sensor 9.

On the other hand, the laser beam L ₁₂ diverges after being condensed at the focal point P, is irradiated onto the surface of the lens 4 that includes a first surface 4a. A part of the laser beam L ₁₂ is reflected as a test surface reflected light beam L _{3 on} the first surface 4 a, travels substantially backward in the optical path of the laser beam L ₁₂ , and is collected near the condensing point P. Then, the light re-enters the condenser lens 33, is emitted upward as a substantially parallel light beam, and reaches the beam splitter 34. A part of the light passes through the beam splitter 34 and is collected by the condenser lens 10, and then reaches the image sensor 9.
Thus, the beam splitter 34, interference fringes in accordance with the optical path difference between the reference surface reflection light beam L ₄ and the test surface reflection light beam L ₃ is formed. The interference fringe image is picked up by the image pickup device 9 and sent to the image acquisition unit 80 of the measurement control unit 8A as a video signal.
Meanwhile, since travel different optical paths also the test surface reflection light beam L ₃ as a reflected light of laser light L ₁₂ emitted to the outside of the mounting surface 4c of the first surface 4a is re-entering the condenser lens 33, the other As in the case of the measurement unnecessary light, it hardly reaches the image pickup device 9.

Further, in a state where the surface top Q of the first surface 4a is substantially coincident with the condensing point P, an interference fringe image having substantially zero fringes can be formed by the interferometer 40 as in the above embodiment.
You

Thus, according to the interferometer 40, since the interference fringe image of the first surface 4a can be acquired in the same manner as the interferometer 30, the spherical center position measuring step S1 and the surface are performed in the same manner as in the above embodiment. The top position measurement step S2 and the curvature radius calculation step S3 can be performed. Also, the ball missing diameter measuring step S4 and the ball missing height calculating step S5 can be performed in exactly the same manner.
Accordingly, the ball notch height measuring device 51 is a modification of the ball notch height measuring device 50 for performing the ball notch height measuring method of the above embodiment.

Moreover, this modification can also measure a sphere defect height by the method different from the said embodiment as a modification of the sphere defect height measuring method of the said embodiment.
That is, sagittal height measuring device 51 of the present modification is provided with the shutter 37, by advancing the shutter 37 in the optical path of the laser beam L _10, the reference surface reflection light beam L ₄ to the beam splitter 34 It can be prevented from entering.
In this case, since only the test surface reflected light beam L ₃ reaches the image sensor 9, a circular image having a diameter d ₀ with no interference fringes is acquired from the image sensor 9.
Therefore, in the spherical center position measuring step S1, the test surface reflected light beam L is temporarily closed by closing the shutter 37 instead of the interference fringe image I ₀ as an image for measuring the spherical missing diameter in the spherical missing diameter measuring step S4. ₃ can obtain a circular image without interference fringes. The obtained circular image is similarly stored in the storage unit 83 and the interference fringe image I _0.
In this way, in the sphere missing diameter measurement step S4, it is only necessary to obtain the outer diameter of the circular image without interference fringes, so that it is not necessary to perform processing for removing the fringe image portion of the interference fringe images. Therefore, the spherical missing diameter D can be obtained by simpler image processing.

In the above description, the example in which the sphere missing diameter D is calculated by fitting a circle in the sphere missing diameter measuring step S4 has been described. However, the calculation method is not limited to this.
For example, the vertical and horizontal diameters may be obtained from the width of the graph obtained by summing the vertical and horizontal luminance values of the pixel array of the image sensor 9 and averaged.

  In the above description, the measurement of the spherical missing diameter D has been described with an example in the case of performing image processing. However, for example, the measurer observes the interference fringe image on the display screen 23a, and the position on the display screen 23a. A cursor line for image measurement indicating the like is displayed, and the measurer moves the cursor line through the operation unit 25 to designate a measurement position on the interference fringe image I0. Based on such designation input, the calculation unit 82 is displayed. May calculate the spherical diameter D.

In the above description, the image of the lens surface to be measured used for the measurement of the spherical missing diameter is described as an example in the case of using the image stored in the calculation unit 82 in the spherical center position measuring step S1, but the spherical center position measurement is performed. without storing the image in step S1, stores only the height H ₁ of the vertical movement mechanism 13, after the radius of curvature measurement process is completed, again by moving the vertical movement mechanism 13 to the position of a height H ₁ Alternatively, an image of the lens surface S to be measured may be acquired, and the spherical diameter measurement may be performed using this image.
In this way, when measuring the sphere diameter without using image processing, for example, the image is observed on the monitor 23, the cursor line for image measurement is displayed on the display screen 23a, and the position of the cursor line is read. In the case of measuring the spherical diameter, the storage space of the storage unit 83 can be reduced.

  In addition, all the components described in the above embodiments and modifications can be implemented by appropriately changing or deleting combinations within the scope of the technical idea of the present invention.

4 Test lens 4E ₀ Outline 4a First surface 4e Lens surface contour 5 Reference lens 5a Reference surface 8, 8A Measurement control unit (curvature radius measurement unit)
9 Image sensor (imaging part)
13 Vertical movement mechanism (movement mechanism)
14 Length measuring device (travel distance measuring unit)
23 Monitor (display unit)
23a Display screen 25 Operation unit 30, 40 Interferometer 50 Sphere missing height measuring device 80 Image acquiring unit 81 Device control unit 82 Computing unit (arithmetic processing unit, sphere missing height calculating unit)
83 Storage Unit 84 Display Control Unit 85 Image Processing Unit (Calculation Processing Unit)
C optical axis D sphere missing diameter F region O sphere center P condensing point Q surface apex R radius of curvature S test lens surface I ₀ , I ₁ interference fringe images L ₀ , L ₁ , L ₂ , L ₁₀ , L ₁₁ , L ₁₂ laser beam (coherent light beam)
L ₃ test surface reflection light beam (reflected light beam at the sample lens surface)
L ₄ reference surface reflection light beam (the other by the reflected light beam of the coherent light beam at the reference plane)
S0 Curvature radius measurement step S1 Sphere center position measurement step S2 Surface apex position measurement step S3 Curvature radius calculation step S4 Sphere missing diameter measurement step S5 Sphere notch height calculation step

Claims (6)

A method for measuring the height of a sphere of a lens for measuring the height of a sphere on a lens surface to be tested having a sphere shape,
A reference surface for acquiring an interference fringe image of the surface of the lens to be tested, splitting the coherent luminous flux and emitting one of the coherent luminous fluxes as a condensed luminous flux toward a condensing point; The interferometer that interferes the reflected light beam on the lens surface to be detected and the reflected light beam on the reference surface by the other of the coherent light beam is arranged on the object to be arranged coaxially with the optical axis of the condensed light beam. Relative movement of the test lens surface in the direction along the optical axis and observing the interference fringe image acquired by the interferometer make the condensing point the spherical center position and the surface top position of the test lens surface. To obtain the relative movement position of the test lens surface in the direction along the optical axis when it coincides with each other, and measure the radius of curvature of the test lens surface by measuring the distance between the relative movement positions A radius of curvature measurement process,
Observing an image of the test lens surface when the condensing point is coincident with the spherical center position of the test lens surface, and measuring the spherical diameter of the test lens surface from the image Measuring process;
A sphere notch height calculating step for calculating a sphere nose height of the lens surface to be measured using the radius of curvature measured in the radius of curvature measurement step and the sphere nose diameter measured in the sphere nose diameter measuring step. When,
A method for measuring the height of a sphere of a lens, comprising: The curvature radius measuring step includes
Storing an interference fringe image of the test lens surface when the focal point is matched with the spherical center position of the test lens surface;
The spherical missing diameter measuring step includes
2. The sphere missing height of the lens according to claim 1, wherein the sphere missing diameter of the lens surface is measured using the interference fringe image stored in the curvature radius measuring step as an image of the lens surface to be examined. Measuring method. The spherical missing diameter measuring step includes
The spherical diameter is measured by performing image processing on an image of the test lens surface, obtaining an outer diameter of the image, and converting the image to a size at a position of the test lens surface. 3. A method for measuring the height of a sphere of a lens according to 1 or 2. A sphere notch height measuring device for a lens for measuring the sphere notch height of a lens surface to be tested having a sphere notch shape,
A reference surface for acquiring an interference fringe image of the surface of the lens to be tested, splitting the coherent luminous flux and emitting one of the coherent luminous fluxes as a condensed luminous flux toward a condensing point; An interferometer that causes a reflected light beam on the surface of the subject lens to interfere with a reflected light beam on the other side of the coherent light beam on the reference surface;
A moving mechanism for moving the lens surface, which is arranged coaxially with the optical axis of the condensed light beam, relative to the interferometer in a direction along the optical axis;
A movement distance measuring unit that acquires a relative movement position of the lens surface to be examined by the movement mechanism, calculates a difference between the relative movement positions, and measures a movement distance between two positions;
An imaging unit that captures an image of the reflected light beam on the surface of the lens to be measured and the reflected light beam on the reference surface in the interferometer;
A display unit for displaying an image captured by the imaging unit;
The test lens surface arranged coaxially with the optical axis of the condensed light beam is moved relative to the direction along the optical axis, and the condensing point is located at the spherical center position and the top surface position of the test lens surface. A radius of curvature for measuring the radius of curvature of the lens surface to be tested by measuring the distance between the relative movement positions of the lens surface to be examined in the direction along the optical axis when matched with the movement distance measuring unit. A measuring section;
Spherical missing diameter measurement for measuring the spherical missing diameter of the test lens surface from the image of the tested lens surface imaged by the imaging unit and the curvature radius of the tested lens surface measured by the curvature radius measuring unit. And
Using the moving distance measured by the moving distance measuring unit as the radius of curvature of the lens surface to be tested, the lens surface to be tested using the radius of curvature and the diameter of the sphere measured by the sphere missing diameter measuring unit. Sphere height calculation unit for calculating the sphere height of
An apparatus for measuring the height of a sphere of a lens, comprising: The spherical missing diameter measuring unit is
A storage unit for storing the interference fringe image captured by the imaging unit;
An outer diameter of the interference fringe image stored in the storage unit is calculated, and the outer diameter is measured on the lens surface by using the curvature radius of the lens surface measured by the curvature radius measurement unit. An arithmetic processing unit that calculates the spherical diameter by converting into a distance;
The sphere missing height measuring device for a lens according to claim 4, comprising: The arithmetic processing unit includes:
6. The lens ball defect height measuring device according to claim 5, wherein the interference fringe image stored in the storage unit is subjected to image processing to calculate an outer diameter of the interference fringe image.

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