JP2016180700A - Surface shape measuring device, surface shape measuring method, and processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and accurately correct an error in measurement of an aspherical shape at low cost.SOLUTION: A surface shape measurement device comprises: a wave surface measurement part that measures a first wave surface that is a wave surface of reflected light from a reference surface in a detection part on the basis of an output from the detection part while the reference surface is arranged at a predetermined position, and a second wave surface that is a wave surface of reflected light from an inspection target surface in the detection part on the basis of an output from the detection part while the inspection target surface is arranged at a predetermined position; a system error calculation part that calculates a system error caused by an optical system from the first wave surface; an alignment error calculation part that calculates an alignment error caused by the position of the inspection target surface from the second wave surface; and a surface shape calculation part that calculates the shape of the inspection target surface from the first wave surface and the second wave surface, calculates an error in measurement of the shape of the inspection target surface from a result of calculation of the shape of the inspection target surface, the system error, and the alignment error caused by the position of the inspection target surface, and corrects the result of calculation of the shape of the inspection target surface by using the measurement error.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a surface shape measurement technique for an optical element, and more particularly to a surface shape measurement technique for an optical element having an aspherical shape.

  As a method for measuring the surface shape of an aspherical lens in a non-contact and high-speed manner, a spherical surface of light is irradiated onto the aspherical surface to be measured via an optical system, and the reflected light from the surface to be measured is reflected. Patent Document 1 proposes a measurement method using a Shack-Hartmann sensor of a light receiving unit. In addition, in order to perform an aspherical surface shape with high accuracy, it is necessary not only to correct measurement errors (so-called system errors) inherent to the measurement apparatus with high accuracy, but also to reduce the alignment error of the lens to be measured. .

  In Patent Literature 1, the shape of the reference lens is measured in advance by separately measuring with a stylus-type measuring machine or the like, and the system error is corrected by taking the difference between the reference lens and the test lens. In Patent Document 2, a measurement error caused by an alignment error of a test lens is calculated in advance, and an alignment error amount at the time of measurement of the test lens is measured to correct the measurement error due to the alignment error.

JP 2012-132682 A JP 2010-25648 A

W. H. Southwell, “Wave-front estimation from wave-front slope measurement”, J. Am. Opt. Soc. Amr. 70, pp998-1006, 1980

  However, in Patent Document 1, if the difference in shape between the reference lens and the test lens or the alignment error between the test lens is large, the difference in measurement error between the reference lens and the test lens becomes large, and correction cannot be performed simply by taking the difference. In Patent Document 2, when the measurement error caused by the alignment error changes depending on the system error of the measurement apparatus or the shape of the lens to be measured, it cannot be corrected with high accuracy.

  The present invention provides an aspheric surface shape measuring device, an aspheric surface shape measuring method, and a processing device capable of correcting a measurement error that occurs depending on a lens shape to be examined, a system error, and an alignment error.

  A surface shape measuring apparatus according to one aspect of the present invention includes a detection unit that detects reflected light from a test surface that is disposed at a predetermined position, an optical system that guides the reflected light to the detection unit, and a detection unit. And a control unit that measures the shape of the surface to be measured based on the output of. The control unit, based on the output from the detection unit in a state where a reference surface having a known shape is arranged at a predetermined position, a first wavefront that is a wavefront in the detection unit of reflected light from the reference surface, A wavefront measuring unit that measures a second wavefront that is a wavefront in the detection unit of reflected light from the test surface based on an output from the detection unit in a state where the surface is arranged at a predetermined position; and a first wavefront A system error calculation unit that calculates a system error caused by the optical system from the first, an alignment error calculation unit that calculates an alignment error caused by the position of the test surface from the second wavefront, a first wavefront and a second wavefront The shape of the test surface is calculated from the calculation result of the test surface, the measurement error of the shape of the test surface is calculated from the calculation result of the test surface shape, the system error, and the alignment error caused by the position of the test surface. Using the calculation result of the shape of the test surface Characterized in that it and a surface shape calculation unit that corrects.

  The surface shape measuring method as another aspect of the present invention is based on an output from a detection unit in a state where a reference surface having a known shape is arranged at a predetermined position, and a wavefront in a detection unit of reflected light from the reference surface. Based on an output from the detection unit in a state where the first wavefront is measured and the test surface is arranged at the predetermined position, the second wavefront in the detection unit of the reflected light from the test surface A step of measuring a wavefront; a step of calculating a system error caused by the optical system from the first wavefront; a step of calculating an alignment error caused by the position of the test surface from the second wavefront; and the first wavefront And measuring the shape of the test surface from the step of calculating the shape of the test surface from the second wavefront, the calculation result of the test surface shape, the system error, and the alignment error caused by the position of the test surface Calculate error And step, using the measurement error, characterized in that it and a step of correcting the calculation result of the shape of the surface.

  According to the present invention, the measurement error of the shape of the test lens can be corrected at low cost at high speed and with high accuracy in consideration of the shape difference between the reference surface and the test surface, the alignment error, and the system error of the apparatus.

Schematic which shows calibration of the aspherical surface measuring apparatus which is Example 1 and Example 2 of this invention. The conceptual diagram in the control part in Example 1 and Example 2. FIG. 6 is a flowchart illustrating an outline of a measurement method according to the first embodiment and the second embodiment. 3 is a flowchart showing a preprocessing flow in the first embodiment. 3 is a flowchart showing a measurement flow in the first embodiment. 3 is a flowchart showing an analysis flow in the first embodiment. 5 is a flowchart showing a correction flow in the first embodiment. 9 is a flowchart showing a preprocessing flow in Embodiment 2. 9 is a flowchart showing a measurement flow in the second embodiment. 9 is a flowchart showing an analysis flow in the second embodiment. 9 is a flowchart showing a correction flow in the second embodiment. Schematic which shows the structure of the optical element processing apparatus which is Example 3 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a configuration of an aspheric surface shape measuring apparatus 100 (hereinafter simply referred to as a measuring apparatus) according to a first embodiment of the present invention. In the following description, the xyz orthogonal coordinate system shown in FIG. 1 is used.

  In FIG. 1, 1 is a light source, 2 is a condenser lens, 3 is a pinhole, 4 is a half mirror, 5 is a light projection lens, 6 is an imaging lens, 7 is a sensor (detector), 8 is a controller, 9 Is a reference lens, and 10 is a test lens. One surface of the reference lens 9 is a reference aspherical surface 9a (hereinafter simply referred to as a reference surface). One surface of the test lens 10 is a test aspheric surface 10a (hereinafter simply referred to as a test surface). In FIG. 1, the reference surface 9a and the test surface 10a are convex surfaces.

  The light from the light source 1 is condensed toward the pinhole 3 by the condenser lens 2. The spherical wave from the pinhole 3 passes through the half mirror 4 and is converted into convergent light by the light projection lens 5. The convergent light is reflected by the reference surface 9 a or the test surface 10 a, passes through the projection lens 5, is reflected by the half mirror 4, passes through the imaging lens 6, and enters the sensor 7.

  The light source 1 is a monochromatic laser, a laser diode, or a light emitting diode. The pinhole 3 is provided for producing a spherical wave with small aberration. Therefore, a single mode fiber may be used instead of the pinhole 3.

  The convergent light applied to the surface 10a to be examined is a convergent spherical wave, and its reflection angle depends on the amount of aspherical surface (deviation from the spherical surface) and the shape error. The angle is significantly different from the incident angle. As a result, the light ray angle measured by the sensor 7 also becomes a large value.

  The reference lens 9 is a lens manufactured using the same parameters (design values) as those of the test lens 10, and the difference in shape between the reference surface 9a and the test surface 10a is several tens of μm or less. In addition, the shape of the reference surface 9 a is measured in advance with high accuracy by a device different from the measuring device 100, for example, a stylus-type measuring device, and the shape data is stored in the control unit 8.

  The sensor 7 includes a microlens array in which a large number of micro condensing lenses are arranged in a matrix and a light receiving sensor such as a CCD, and is generally called a Shack-Hartmann sensor. In this sensor, the light beam transmitted through the minute condenser lens is condensed on the light receiving sensor for each minute condenser lens. The angle Ψ of the light beam incident on the sensor 7 is obtained by detecting the difference Δp between the position of the spot condensed by the minute condenser lens and the position calibrated in advance, for example, the spot position when parallel light is incident. Desired. Here, the difference Δp between the angle Ψ of the light beam and the spot position satisfies the relation Ψ = atan (Δp / f), where f is the distance between the microlens array and the light receiving sensor (CCD). By performing the above processing on all the minute condensing lenses, the angular distribution of the light beam received by the sensor 7 can be measured.

  The sensor 7 is not limited to the Shack-Hartmann sensor, but may be a shearing interferometer or a Talbot interferometer that includes, for example, a diffraction grating and a light receiving sensor, as long as it can measure the wavefront or the angular distribution of light rays.

  When the diameter of the reflected light from the test surface is larger than the light receiving surface of the sensor 7, for example, a sequence of measuring only a part of the reflected wavefront and moving the sensor 7 is repeated a plurality of times, and the measurement data is joined together. Find the overall wavefront and angular distribution.

  The control unit 8 is constituted by a microcomputer including a CPU and the like, and includes a wavefront measuring unit 12, a system error calculating unit 13, an alignment error calculating unit 14, and an analysis calculating unit 15 as shown in FIG. With this configuration, the calculation described later is performed based on the output from the sensor 7. In order to finish the test surface 10a into a target shape, the abscissa and correction amount for performing correction processing on the test surface 10a are determined from the difference between the surface shape measurement data obtained by the measuring apparatus 100 and the target shape data. Calculation is performed and correction processing is performed by the processing unit of the processing apparatus described in the third embodiment.

  Hereinafter, the measurement sequence of Example 1 will be described with reference to FIGS. 3 and 4.

  As shown in FIG. 3, the measurement sequence according to the first embodiment includes four flows: a preprocessing flow A, a measurement flow B, an analysis flow C, and a correction flow D. In the preprocessing flow A, the reference lens is measured by another measuring device, for example, a stylus type measuring device. In the measurement flow B, the light beam angle distribution of the reflected light of the reference lens and the test lens is measured by the sensor 7. In the analysis flow C, the approximate shape of the surface to be measured is calculated by converting the measured light ray angle distribution on the sensor into a light ray angle distribution on the lens surface and integrating it. In the correction flow D, a measurement error of the test lens shape caused by the difference in shape between the reference lens and the test lens, the alignment error, and the system error of the apparatus is obtained and corrected. As a result, high-precision measurement can be performed with a low-cost apparatus, and further, alignment of the lens to be examined is not necessary, so that measurement can be performed at high speed.

  Hereinafter, the above four flows will be described with reference to the flowcharts of FIGS. 4A to 4D.

  In Step A-1, the surface shape of the reference surface 9a is measured by another measuring device capable of measuring the shape with high accuracy, for example, a stylus type measuring device. That is, the reference surface 9a on which the shape is measured is prepared. The measurement shape of the reference surface 9a is assumed to be FIGB.

In step A-2, the analysis calculation unit 15 calculates the wavefront W _bcal of the reference surface 9a on the light receiving surface 7a (hereinafter also referred to as sensor surface) of the sensor 7 (hereinafter also referred to as the calculation wavefront W _bcal ). For this calculation, the shape data of the reference surface 9a obtained by the measurement in step A-1 and the parameters of the optical system of the measuring apparatus 100 are used. The wavefront is calculated using ray tracing software.

Here, the parameters of the optical system (hereinafter referred to as optical system parameters) are mainly the radius of curvature and refractive index of the optical elements such as lenses and mirrors constituting the optical system, and the spacing and decentration of the optical elements. In other words, it can be rephrased as a design value (design value data) of the optical system, including the wavelength. The optical system parameters are not limited to those described above, and may be information such as wavefront aberrations generated in the optical system, or the like. When the aberration and assembly error of the optical system and the surface shape of the lens are known or can be measured, the analysis calculation unit 15 calculates the wavefront W _{bcal of the} reference surface by reflecting those values on the design value of the optical system. By reflecting the measurement information on the design value, the wavefront W _{bcal of the} reference plane can be calculated more accurately. The wavefront may be expressed by a Zernike function that is an orthogonal function.

  In Step B-1, the reference lens 9 is installed on a stage (predetermined position) (not shown) of the measuring apparatus 100.

In step B-2, the alignment error calculation unit 14 calculates the alignment error of the reference lens 9 with respect to the position (eccentricity) in the xy plane and the inclination with respect to the xy plane, and performs alignment of the reference lens 9 based on the calculation. This alignment is performed so that the tilt and the coma aberration coefficient of the wavefront W _b (hereinafter also referred to as the measurement wavefront W _b ) of the light reflected by the reference surface 9a measured in Step B-3 described later become small. ). Threshold values relating to lens alignment, such as eccentricity 1 um and inclination 50 urad, are set in advance, and alignment is completed when the threshold values are cleared. An alignment residue related to eccentricity or inclination is called an alignment error. Alignment error amount when the lens is aspheric, a tilt and coma aberration coefficient of the measurement wavefront W _b, a lens that is easily computed from the change in the tilt and the coma aberration coefficient when the drive unit amount (sensitivity) it can.

In step B-3, after the alignment is completed, the wavefront measurement unit 12 measures the ray angle distribution (wavefront W _b ) of the reflected light of the reference surface 9a in this state, and stores the data U1 in the control unit 8.

  In step B-4, the reference lens 9 is retracted from the stage, and the test lens 10 is placed on the stage (predetermined position).

In Step B-5, the wavefront measuring unit 12 measures the ray angle distribution (wavefront W _s ) of the reflected light of the test surface 10a in this state, and stores the data U2 in the control unit 8. The test lens 10 is not aligned as in step B-2. However, the alignment error is suppressed to the extent that the reflected light from the test surface 10a passes through the effective diameters of the lenses 5 and 6.

In Step C-1, the system error calculation unit 13 calculates a _difference between the calculated wavefront W _bcal of the reference plane calculated in Step A-2 and the measured wavefront W _b of the reference plane measured in Step B-3. Since the calculation wavefront W _bcal reflects the shape of the reference surface 9a, the difference between the calculation wavefront W _bcal and the measurement wavefront W _b is a system error W _sys . The system error W _sys occurs because optical parameters for calculation and measurement are different due to the effects of lens manufacturing error, holding deformation, and assembly error.

In Step C-2, from the wavefront _{W s} of the alignment error calculation unit 14 is measured in step B-5, the alignment error amount A of the lens 10 (ξ, η, Qx, Qy) calculates a. ξ and η are decentering error amounts in the xy direction of the test lens 10, and Qx and Qy are tilt error amounts with respect to the xy plane.

In Step C-3, the light ray angle distribution (wave surface W _b ) on the sensor 7 of the reference surface 9a measured by the analysis calculation unit 15 in Step B-3 is used to perform the reverse ray tracing using the ray tracing software on the reference surface 9a. The position (X, Y) and angle Vb of the light beam at are calculated. The _reverse ray tracing uses the same optical parameter as the optical parameter obtained by calculating the wavefront W _bcal of the reference plane in step A-2. Similarly, the analysis calculation unit 15 uses the ray angle distribution (wavefront W _s ) on the sensor 7 of the test surface 10a measured in step B-5 to perform the ray tracing on the test surface 10a by back ray tracing. The position (X, Y) and the angle Vs are calculated. The slopes tan (Vb) and tan (Vs) of the reference surface 9a and the test surface 10a are the differential values of the surface shapes of the reference surface 9a and the test surface 10a. This is the sum of the differential values of system errors that occur due to differences. Next, the analysis calculation unit 15 calculates W1 and W2 by dividing the slopes tan (Vb) and tan (Vs) of the reference surface 9a and the test surface 10a by the following formula.

  Here, FIG. B represents the surface shape of the reference surface 9a, FIG. S represents the surface shape of the test surface 10a, Sys B represents the system error during measurement of the reference surface, and Sys S represents the system error during measurement of the test surface. ΔW represents the difference between W1 and W2, ΔFig is the difference in shape between the reference surface 9a and the test surface 10a, and δS is the difference in system error between the surface shapes of the reference surface 9a and the test surface 10a. With respect to the algorithm for integrating the slope, using the differential function of the basis function, fitting is performed on the slope difference, the method of multiplying the obtained coefficient and the basis function (modal method), and the method of adding the slope ( zonal method). These are described in a plurality of documents such as Non-Patent Document 1. In Equation 2, the difference between the results of dividing the slopes of the reference lens 9 and the test lens 10 into areas is taken, but the slope difference between the reference lens 9 and the test lens 10 may be integrated.

  In step C-4, the analysis calculation unit 15 adds the shape FIG. B of the known reference surface 9a separately measured in step A-2 to the measurement result ΔW in step C-3, thereby roughly testing the test surface 10a. The surface shape FigMS is calculated.

  As in the above equation, the calculated approximate shape of the test surface 10a includes an unknown measurement error δS.

The shape error δS occurs when light reflected by the reference surface 9a and the test surface 10a passes through different optical paths in the optical system. If the reference lens 9 and the test lens 10 are aspherical surfaces having the same design value, the optical path difference is small and the system error δS is small. However, even if the reference surface 9a and the test surface 10a have the same design value, if the shape difference ΔFig is large, or if the alignment error amount A of the test lens 10 is large, a difference occurs in the optical path that passes. Also, the measurement error δS due to the difference in the optical path increases in proportion to the system error W _sys . Therefore, δS can be expressed as a function δS (ΔFig, A, W _sys ) depending on the shape difference ΔFig between the reference surface 9a and the test surface 10a, the alignment error A, and the system error W _sys . If δS is reduced by reducing ΔFig, A, and W _sys , the shape of the test surface can be measured with high accuracy. However, reducing ΔFig means that the measurement range is narrowed. Further, in order to reduce A, a driving mechanism for highly accurate alignment is necessary, and the measurement time for alignment also increases. In addition, in order to reduce the system error W _sys , it is necessary to assemble an optical system manufactured with high accuracy with high accuracy. Therefore, the following correction flow D is used to estimate δS and remove the value from the approximate test surface shape FIGMS to realize highly accurate measurement of the test surface shape.

In step D-1, the analysis calculation unit 15 estimates the optical system parameters in the calculation so that the system error W _sys, which is the difference between the calculation wavefront W _bcal and the measurement wavefront W _b , is small (preferably minimized). ,change. There are no restrictions on the optical system parameters to be changed, and an arbitrary phase distribution may be added to the virtual surface as well as the surface shape and surface interval of the optical element. As a technique for reducing the difference between the calculation wavefront W _bcal and the measurement wavefront W _b , a technique that uses the sensitivity of the wavefront W _bcal when the optical parameter is changed, or the most likely optical that reproduces the measurement wavefront W _b on the calculation. There is a method using a maximum likelihood method for estimating parameters. Here, it is important that the difference between the calculation wavefront W _bcal and the measurement wavefront W _b is small. Even if the optical parameters at the time of calculation and actual measurement are different, it is sufficient that the difference between the two wavefronts is sufficiently small.

In step D-2, the analysis calculation unit 15 (surface shape calculation unit) uses the optical system parameters changed in step D-1 and the shape FigB of the reference surface 9a on the sensor 7 of the reference surface 9a using the ray tracing software. _Is calculated (wavefront W _bcal ′).

  In Step D-3, the approximate test surface shape FigMS of the test surface 10a calculated in Step C-4 and the alignment error A of the test lens 10 calculated in Step C-2 are input, and the test lens information is input. As reflected in the calculation in step D-4.

In step D-4, the analysis calculation unit 15 reflects the alignment error A, and from the optical parameters changed in step D-1 and the approximate test surface shape FigMS, the sensor 7 on the test surface 10a is detected using the ray tracing software. The ray angle distribution (wavefront W _scal ) above is calculated.

In Step D-5, ray angle distribution of the reference surface 9a and the test surface 10a to the analysis operator 15 is calculated in step D-2 and Step D-4 (the wavefront _{W bcal} 'and wavefront _{W scal),} Step A- In step 2, the ray is traced using the optical parameters used for the wavefront calculation of the reference plane. Thereby, similarly to step C-3, the slope of the reference surface 9a and the test surface 10a is obtained. Then, the analysis operation part 15, by equations 2 and 3 from the slope, calculates a shape _{F cal} of the test surface 10a corresponding to FigMS of formula 3.

Step D-4 ray angle distribution of the test surface 10a calculated in (wavefront W _scal) as actual specimen surface geometric schematic specimen surface geometric FigMS, those computed to reflect the alignment error A . Therefore, considering that the general test surface shape obtained from the wavefront _{W s} measured in step B-5 is a FigMS = FigS + δS, similar in test surface shape obtained from the wavefront _{W scal} the above method F _cal = FigMS + δS _cal δS _cal is a measurement error of the test surface shape that occurs under the conditions of the test surface shape FigMS, the test surface alignment error A, and the system error W _sys of the measurement apparatus 100.

Therefore, in step D-6, the analysis calculation unit 15 subtracts the test surface shape FIGMS input in step D-3 from the test surface shape F _cal obtained in step D-5 to calculate the difference δS _cal .

Since the alignment error A is obtained from the wavefront W _s in step C-2, a relationship of δS≈δS _cal is established. Therefore, in step D-7, δS _cal is subtracted from the result FIGMS computed by the analysis computation unit 15 in step C-4 to obtain the true test surface shape F _real .

If the calculation result of step D-3 and step D-4 is repeatedly performed with _Freal as the approximate test surface shape, the test surface shape can be measured with higher accuracy.

With the above configuration, the test surface shape measurement error δS (ΔFig, A, W _sys ) depending on the shape difference ΔFig, the alignment error A, and the system error W _sys between the reference surface 9a and the test surface 10a is corrected in calculation. be able to. As a result, even if ΔFig is large, measurement can be performed with higher accuracy than in the past, and the measurement area can be expanded. In addition, since the alignment of the test surface 10a is not necessary, high-speed measurement can be performed. Furthermore, since high-precision measurement is possible even if the system error is large, manufacturing and assembly costs can be reduced.

  Since the measuring apparatus 100 includes a lens alignment mechanism for aligning the reference lens 9, when importance is attached to high-precision measurement, the test surface is set after setting the alignment error A of the test lens to be equal to or less than the alignment threshold value. Measurement of 10a may be performed.

  The calculation in the control unit 8 may be performed inside the measurement apparatus 100 as described in the present embodiment, or measurement data may be output to an external computer and the calculation may be performed by the external computer. . The calculation in the external computer may be only a part of the calculation shown in this embodiment.

  Next, an aspheric shape measurement method according to the second embodiment of the present invention will be described with reference to FIGS. 5A to 5D. The contents overlapping with those of the first embodiment are omitted.

In the first embodiment, in order to obtain the system error W _sys in step C-1, it is necessary to set the alignment error of the reference surface 9a to a threshold value or less in step B-2. However, since the system error W _sys is an error due to an optical system manufacturing error or assembly error, the change in a short period is sufficiently small. Therefore, once the system error W _sys is obtained in step C-1 by the system error calculation unit 13, it is not necessary to align the reference surface 9a with high accuracy when newly measuring the test surface 10a. That is, step B-2 of the measurement flow B described in FIG. 4 is not necessary.

  FIG. 5 shows a pre-process flow A, a measurement flow B, an analysis flow C ′, and a correction flow D ′ in the second embodiment. Unlike the first embodiment, step B-2 is not necessary, and in step C'-1, the alignment error calculator 14 calculates the alignment error Ab of the reference lens 9 instead of the known system error.

In step D′-1, since the optical system parameters have already been estimated, the alignment error Ab of the reference lens 9 is input. In step D′-2, the ray angle distribution (wavefront W _bcal ′) of the sensor 7 on the reference surface 9a is calculated from the optical parameters estimated by the analysis calculation unit 15 and the shape FIG. ) Is calculated. The difference from the first embodiment is that the ray angle distribution (wavefront W _bcal ′) is calculated by reflecting not only the shape FIG. B of the reference surface 9a but also the alignment error Ab of the reference lens 9. Steps after Step D′-2 are the same as those in the first embodiment.

In this embodiment, the measurement error δS _cal is obtained by calculating the alignment error Ab of the reference lens 9 using a known system error. For this reason, not only the test lens 10 but also the reference lens 9 need not be aligned, and higher-speed measurement is possible.

  The calculation in the control unit 8 may be performed inside the measurement apparatus 100 as described in the present embodiment, or measurement data may be output to an external computer and the calculation may be performed by the external computer. . The calculation in the external computer may be only a part of the calculation shown in this embodiment.

  FIG. 6 shows a configuration of an optical element processing apparatus 200 using the aspheric surface shape measuring apparatus 100 described in the first and second embodiments as the third embodiment of the present invention.

  Reference numeral 11 denotes a material (raw material) of the test lens 10, and 201 denotes a processing unit that manufactures the test lens 10 as an optical element by performing processing such as cutting and polishing on the material 11.

  The surface shape of the test surface 10a of the test lens 10 processed by the processing unit 201 is measured using the aspheric surface measurement method described in the first embodiment in the aspheric surface shape measuring apparatus 100 as the measurement unit. . Then, as described in the first embodiment, the measuring apparatus 100 is configured to perform measurement on the basis of the difference between the measurement data of the surface shape of the test surface 10a and the target data in order to finish the test surface 10a to the target surface shape. The amount of correction processing for the inspection surface 10a is calculated and output to the processing unit 201. As a result, correction processing is performed on the test surface 10a by the processing unit 201, and the test lens 10 having the test surface 10a reaching the target surface shape is completed.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  It is possible to provide a measuring method and a measuring apparatus capable of measuring the shape of the test surface at high speed and with high accuracy.

4 Half mirror 5 Projection lens 6 Imaging lens 7 Sensor 8 Control unit 9 Reference lens 9a Reference surface 10 Test lens 10a Test surface 12 Wavefront measurement unit 13 System error measurement unit 14 Alignment error calculation unit 15 Surface shape calculation unit

Claims (11)

A detection unit for detecting reflected light from a surface to be measured arranged at a predetermined position;
An optical system for guiding the reflected light to the detection unit;
A surface shape measuring device comprising: a control unit that measures the shape of the test surface based on an output from the detection unit;
The controller is
Based on an output from the detection unit in a state where a reference surface having a known shape is disposed at the predetermined position, a first wavefront that is a wavefront in the detection unit of reflected light from the reference surface, and the target A wavefront measuring unit that measures a second wavefront that is a wavefront in the detection unit of reflected light from the test surface based on an output from the detection unit in a state where the test surface is arranged at the predetermined position When,
A system error calculation unit for calculating a system error caused by the optical system from the first wavefront;
An alignment error calculator that calculates an alignment error caused by the position of the test surface from the second wavefront;
The shape of the test surface is calculated from the first wavefront and the second wavefront, and from the calculation result of the shape of the test surface, the system error, and the alignment error caused by the position of the test surface, A surface shape calculation unit that calculates a measurement error of the shape of the test surface and corrects a calculation result of the shape of the test surface using the measurement error;
A surface shape measuring device comprising:   The surface shape calculation unit estimates an optical system parameter from the system error, and uses the optical system parameter to calculate the shape of the test surface and an alignment error caused by the position of the test surface. The surface shape measuring apparatus according to claim 1, wherein a measurement error is calculated.   The system error calculation unit calculates a wavefront at the detection unit from the known shape of the reference plane, and calculates the system error by obtaining a difference between the wavefront and the first wavefront. The surface shape measuring device according to claim 2.   The surface shape measuring apparatus according to claim 3, wherein the surface shape measuring apparatus estimates the optical system parameter that minimizes the difference.   5. The surface shape measurement apparatus according to claim 2, wherein the surface shape calculation unit estimates the optical system parameter from the system error by a maximum likelihood method. 6. The alignment error calculation unit calculates an alignment error caused by the position of the reference plane from the first wavefront,
The surface shape calculation unit uses the optical system parameters to calculate the shape of the test surface from the calculation result of the test surface, the alignment error caused by the reference surface, and the alignment error caused by the position of the test surface. 6. The surface shape measuring device according to claim 2, wherein a surface shape measurement error is calculated.   The surface shape calculation unit calculates the corrected shape of the test surface based on the corrected calculation result of the shape of the test surface, the system error, and the alignment error caused by the position of the test surface. The surface shape measuring apparatus according to claim 1, wherein the result is corrected.   The surface shape measuring apparatus according to claim 1, further comprising a light source that irradiates light to the reference surface and the test surface. The surface shape measuring device according to any one of claims 1 to 8,
A processing apparatus comprising: a processing unit configured to process the test surface based on the shape of the test surface measured by the surface shape measuring device.   An optical element having a test surface processed by the processing apparatus according to claim 9. A surface shape measuring method for measuring the shape of the test surface by detecting reflected light from the test surface arranged at a predetermined position with a detection unit via an optical system,
Measuring a first wavefront which is a wavefront in the detection unit of reflected light from the reference surface based on an output from the detection unit in a state where a reference surface having a known shape is arranged at the predetermined position When,
Measuring a second wavefront that is a wavefront in the detection unit of reflected light from the test surface based on an output from the detection unit in a state where the test surface is arranged at the predetermined position;
Calculating a system error due to the optical system from the first wavefront;
Calculating an alignment error resulting from the position of the test surface from the second wavefront;
Calculating the shape of the test surface from the first wavefront and the second wavefront;
From the calculation result of the shape of the test surface, the system error, and the alignment error caused by the position of the test surface, calculating the measurement error of the shape of the test surface;
Correcting the calculation result of the shape of the test surface using the measurement error;
A surface shape measuring method characterized by comprising: