JP6095294B2 - Measuring method and measuring device - Google Patents

Description

  The present invention relates to a measuring method and a measuring apparatus for measuring the overall shape by acquiring shape information in a plurality of regions of an object to be measured and connecting them together.

  In a measurement method using stitching in which a measured object is divided into a plurality of partial areas and the measured partial areas are joined together, the measured object needs to be tilted, rotated, translated, and the like. Patent Document 1 proposes a method of correcting an installation error, a systematic error, a positional deviation, and the like so as to reduce an error in an overlapping area between partial areas. Patent Document 2 proposes a method of correcting a measurement error accompanying a change in the attitude of the coordinate measuring machine using a parameter table corresponding to the attitude of the coordinate measuring machine. Patent Document 3 proposes a method of correcting a deformation error of a measurement object by subtracting a profile of the measurement object having good flatness from the flatness profile of the measurement object.

US Pat. No. 6,956,657 JP 2007-171077 A JP 05-346325 A

  However, the conventional technology does not consider deformation due to its own weight or holding, and cannot correct this, and it is also impossible to individually correct different deformation for each partial region.

  It is an exemplary object of the present invention to provide a measurement method and a measurement apparatus that can correct the deformation of an object to be measured in stitching.

The measuring method of the present invention is a measuring method for measuring the shape of an object to be measured, and a plurality of partial regions set by dividing the object to be measured on shape information of the object to be measured in different inclined states. For each of the partial areas of the object to be measured, obtaining deformation information by gravity in a corresponding inclined state , and measuring for each of the partial areas. Subtracting the deformation amount information obtained by the obtaining step from shape information; and joining the shape information of the plurality of partial regions obtained by the subtracting step. To do.

  ADVANTAGE OF THE INVENTION According to this invention, the measuring method and measuring apparatus which can correct | amend the dead weight deformation | transformation of a to-be-measured object in stitching can be provided.

It is sectional drawing for demonstrating operation | movement of the measuring apparatus and stage of this invention. (Example 1) It is an expanded sectional view which shows the mode of self-weight deformation in the inclination state from which the to-be-measured object shown in FIG. 1 differs. It is a flowchart of the stitching method performed by the calculating means shown in FIG. (Example 1) It is a figure for demonstrating S105 of FIG. (Examples 1 and 3) It is a flowchart of the stitching method performed by the calculating means shown in FIG. (Example 2) It is an expanded sectional view which shows the mode of self-weight deformation in the inclination state from which the to-be-measured object shown in FIG. 1 differs. Example 3 It is a flowchart of the stitching method performed by the calculating means shown in FIG. Example 3 It is a flowchart of the stitching method performed by the calculating means shown in FIG. Example 4

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

  FIGS. 1A to 1C are cross-sectional views for explaining the operation of the stage on which the object to be measured is mounted, and FIG. 1C also shows the measuring apparatus of this embodiment. The measurement apparatus includes an interferometer 3, an image sensor 10, an A / D converter 11, a calculation unit 12, a system control unit 14, a simulator 16, and a drive unit 18.

  The interferometer 3 has a holding portion 2 and a reference surface 4. In this embodiment, the interferometer 3 is a look-down type interferometer (measuring means) that measures from above to below. The holding unit 2 holds a device under test 1 that is an optical element such as a lens. The holding method by the holding unit 2 is not limited. The interferometer 3 acquires interference fringes between the reflected light from the reference surface 4 and the reflected light from the measured surface 5 of the device under test 1. The focal position of the reference surface 4 and the focal position of the surface to be measured 5 coincide at the confocal position 6.

  The image sensor 10 is composed of a photoelectric conversion element such as a CCD, photoelectrically converts interference fringes acquired by the interferometer, and outputs an analog signal. The A / D converter 11 converts the analog signal into a digital signal. A signal processing circuit (not shown) performs necessary signal processing on the digital signal and provides it to the computing means 12.

  The computing means 12 is composed of a microcomputer (processor). The computing means 12 stitches (joins together) the shape information (data such as shape, wavefront, and tilt) data acquired for each partial region of the device under test 1 in different tilt states. It functions as a stitching means for acquiring the shape information. The plurality of partial areas are set by dividing the DUT 1. The calculation means 12 also functions as a correction means that corrects deformation due to gravity (self-weight deformation) depending on holding and posture of the test object. The correction means subtracts the deformation amount from the shape information of the DUT 1 for each partial region.

  The system control means 14 is composed of a microcomputer (processor) and controls each part of the measuring apparatus. For example, the system control unit 14 is driven by the driving unit 18 that drives the holding unit 2 or a member (not shown) coupled to the holding unit 2 so that the DUT 1 performs at least one of rotation, inclination, and parallel movement. Control the drive. The simulator 16 is an acquisition unit that performs a simulation to be described later and acquires the amount of deformation due to gravity for each partial region of the DUT 1.

  In FIG. 1, the angle (tilt angle) formed by the optical axis 7 indicated by the one-dot chain line of the DUT 1 and the optical axis 8 indicated by the solid line of the interferometer 3 is θy, and the optical axis 7 of the DUT 1 is the rotation axis. The rotation angle is θz. Since the optical axis 7 of the object to be measured moves in conjunction with the tilt angle θy, the rotation axis of θz varies depending on the tilt angle θy.

  FIG. 1A is a schematic diagram when θy = 0 ° and θz = 0 °. FIG. 1B is a schematic diagram when θy = 20 ° and θz = 0. FIG. 1C is a schematic diagram when θy = 20 ° and θz = 180 °. 1B and 1C seem to be the same at first glance, but the position of the holding portion 2 differs depending on the rotation of θz.

  FIG. 2 is an enlarged cross-sectional view showing a state of deformation due to gravity in a different inclined state of the DUT 1. 2A shows θy = 0 ° and θz = 0 °, FIG. 2B shows θy = 10 ° and θz = 0 °, and FIG. 2C shows θy = 10 ° and θz = 180 °. The own weight deformation of the DUT 1 is shown.

  2A to 2C, the dotted line indicates the shape 11 of the DUT 1 when there is no deformation due to its own weight, and the shape 11 is common to the drawings. The shape 11 is a shape in a state where it is not affected by gravity (ie, weightlessness).

  On the other hand, the solid lines shown in FIGS. 2A to 2C show the shapes 12, 13, and 14 of the DUT 1 when there is deformation due to its own weight. Since the influence of gravity is different, the shapes are different. . Since this difference appears as a stitch error, correction is necessary.

  Since the self-weight deformation depends on the inclination angle θy and the rotation angle θz, the present embodiment expresses the self-weight deformation of the DUT 1 as a function of the inclination angle θy and the rotation angle θz, and corrects the stitching accuracy by correcting at the time of stitching. Has improved.

  FIG. 3 is a flowchart of the stitching method executed by the computing means 12, and “S” is an abbreviation for step. The stitching method shown in FIG. 3 can be embodied as a program for causing a computer to execute each step (procedure), and this is the same in FIG.

  In FIG. 3A, in S101, a condition for dividing into partial areas is determined. This can be determined from the design value of the DUT 1 and the size of the interferometer 3 to be used. At this time, the later calculation of the deformation amount can be simplified using the symmetry of the inclination angle θy and the rotation angle θz.

  In S102, the deformation amount G (θy, θz) of the shape of each partial region is simulated using the division condition determined in S101, the design value of the DUT 1 and the simulator 16. That is, using a mechanical CAD or the like, the deformation amount is calculated in consideration of the design value of the DUT 1 and the holding method and gravity in each division condition.

  Since the deformation amount G depends on the tilt angle θy and the rotation angle θz, it can be expressed as a function of θy and θz. For example, the deformation amount in the case of θy = 0 °, 5 °, 10 ° is simulated, and Zernike fit is performed for each. There is a method of defining the amount of deformation at an arbitrary θy by linearly fitting the change in the coefficient of each term. The same applies to θz. This is only an example, and another method may be used, such as fitting a coefficient change with a quadratic function. If there is a correlation between the θz rotational symmetry of the division condition determined in S101 and the rotational symmetry of the holding unit 2, the correlation may be used. For example, even if the θz rotational symmetry of the division condition is six-fold symmetrical, if the rotational symmetry of the holding unit 2 is three-fold symmetrical, substantially two patterns may be considered.

In S103, the number of measurement repetitions is set by the number of partial areas. In S104, the partial region n is measured and the shape information F _n (θy, θz) is acquired. The shape information may be the shape of the DUT 1 or may be the inclination of the wavefront of the light from the DUT 1 as will be described later.

In S105, the self-weight deformation of the partial region n is corrected based on the deformation amount G simulated in S102. FIG. 4 shows an example of S105. Although the entire object to be measured is deformed, the range corresponding to the partial area may be corrected. Of the surface to be measured 5, the inside of the measurable range 24 of the interferometer 3 is measured, and partial region data 25 (F _n (θy, θz)) is acquired. The partial area data 25 is data with deformation. The deformation is corrected by subtracting the deformation amount G (θy, θz) from the partial region data 25.

The deformation amount G (θy, θz) varies depending on the posture of the DUT 1. FIG. 4A is a diagram for explaining deformation correction when θy = 0 ° and θz = 0 °. FIG. 4B is a diagram for explaining deformation correction when θy = 15 ° and θz = 0 °. Due to the difference in θy, the deformation amount G (θy, θz) is different from that in FIG. Different. FIG. 4C is a diagram for explaining deformation correction when θy = 15 ° and θz = 90 °. Due to the difference in θy, the deformation amount G (θy, θz) is different from that in FIG. Different. By calculating F _n (θy, θz) −G (θy, θz) in each partial region data, the self-weight deformation can be corrected.

  In S <b> 106, a partial area data stitching operation (stitching) after correcting the self-weight deformation in S <b> 105 is performed.

  FIG. 3B is a modification of FIG. In FIG. 3 (a), n is updated from 1 to n after obtaining measurement data (S104) and deformation correction (S105) for each partial region, but this is an example. For example, as shown in FIG. 3B, the deformation correction (S105) may be collectively performed for all partial areas after the measurement of S104 is performed for all partial areas. In any case, the deformation correction may be completed before the stitching (S107). As long as the simulation (S102) is also performed before S105, the time does not matter (for example, it may be performed simultaneously with other steps).

  According to the present embodiment, the stitching accuracy can be improved relatively easily by simulating the deformation amount G and expressing it as a function of θy, θz and correcting each of the partial regions.

  In the present embodiment, the deformation amount is acquired by actually measuring, not by simulation. FIG. 5 is a flowchart of a stitching method executed by the calculation means 12 of the present embodiment, and “S” is an abbreviation for a step (process). 5A corresponds to FIG. 3A, FIG. 5B corresponds to FIG. 3B, and the same steps are denoted by the same reference numerals.

  In FIG. 5A, S112 is performed after S101 instead of S102. In S112, the deformation amount G is measured. Therefore, a shape measuring device (acquisition means) (not shown) is provided instead of the simulator 16 of FIG.

  For example, a sample having the same design value (material) as the device under test 1, the actual shape is known, and can be regarded as the device under test 1 (having material and shape) is prepared. Let A be the known shape. And let B be the result of measuring this sample under the splitting conditions determined in S101. Since the measurement result B has a shape deformation shape, the deformation amount G (θy, θz) is obtained by B−A. The rest is the same as in the first embodiment.

  The means for actually measuring the shape deformation is not limited to the method of this embodiment. For example, even if a sample for deformation measurement is not prepared, if there is a holding method (for example, received by a surface) that does not cause deformation, actual measurement may be performed using the object to be measured.

  According to the present embodiment, the stitching accuracy can be improved relatively easily by actually measuring the deformation amount G and expressing it as a function of θy, θz and correcting it for each partial region.

  FIG. 6 is an enlarged cross-sectional view showing a state of deformation due to gravity in a different inclined state of the DUT 1. 6A shows the case of θy = 0 ° and θz = 0 °, FIG. 6B shows the case of θy = 10 ° and θz = 0 °, and FIG. 6C shows the case of θy = 10 ° and θz = 180 °. The own weight deformation of the DUT 1 is shown.

  6A to 6C, the dotted line indicates the shape 31 of the DUT 1 when there is no deformation due to its own weight, and the shape 31 is common to the drawings. The shape 31 is a shape in a state where it is not affected by gravity (ie, weightlessness). The shape 31 is, for example, a spherical surface or an axisymmetric aspheric surface.

  On the other hand, the solid lines shown in FIGS. 6A to 6C show the shapes 32, 33, and 34 of the DUT 1 when there is deformation due to its own weight. Since the shapes 32 to 34 are different in the influence of gravity, they are likely to have different shapes as in FIG. However, the shape 31 is rotationally symmetric with respect to the optical axis 7, the plurality of holding units 2 are arranged to be rotated with respect to the optical axis 7, the θz rotational symmetry of the division condition is n-fold symmetric, and the holding unit 2 A special condition occurs when the rotational symmetry is an integer multiple of n. Note that “the θz rotational symmetry of the division condition is n-fold symmetry” means that the partial region overlaps n times before the DUT 1 rotates 360 °, and “the rotational symmetry of the holding portion 2 is n “An integral multiple rotational symmetry of” means that the holding unit overlaps an integral multiple of n before the DUT 1 rotates 360 °. In this case, the shapes 33 and 34 match, and the deformation error amount does not depend on the rotation angle θz.

  FIG. 4D shows the deformation state when θy = 15 ° and θz = 90 °. FIG. 4B and FIG. 4D are different in θz, but the deformation amount G depends on θz. Therefore, the deformation amount G is the same.

  FIG. 7 is a flowchart of a stitching method executed by the calculation means 12 of the present embodiment, and “S” is an abbreviation for a step (process). FIG. 7A corresponds to FIG. 3A, FIG. 7B corresponds to FIG. 3B, and the same steps are denoted by the same reference numerals. FIG. 7 is different from FIG. 3 except for having S122 in which the deformation amount G (θy, θz) is G (θy) and S115 for subtracting G (θy) instead of G (θy, θz). It is the same. In this embodiment, G is estimated by simulation, but may be obtained by actual measurement as in the second embodiment.

  According to the present embodiment, the stitching accuracy can be improved relatively easily by expressing the deformation amount G as a function of θy and correcting it for each partial region.

  In the first to third embodiments, the interferometer 3 is used as a measuring device, but the present invention is applicable to other measuring devices. For example, you may use the Shack-Hartmann measuring device (measuring means) which measures the inclination of a wave front. In other words, this embodiment uses a Shack-Hartmann measuring device instead of the interferometer 3 shown in FIG.

  FIG. 8 is a flowchart of the stitching method executed by the calculation means 12 of the present embodiment, and “S” is an abbreviation for step (process). 8A corresponds to FIG. 3A, FIG. 8B corresponds to FIG. 3B, and the same steps are denoted by the same reference numerals. FIG. 8 uses S132 for simulating a deformation amount G ′ (θy, θz), which is a derivative of the deformation amount G (θy, θz), instead of S102 for simulating the deformation amount G (θy, θz). Further, S114 for obtaining the wavefront inclination information Fn ′ (θy, θz) is used instead of S104 for obtaining the shape information Fn (θy, θz). Then, S105 is replaced with S125 which executes Fn ′ (θy, θz) −G ′ (θy, θz). Other steps are the same as in the first to third embodiments.

  In this embodiment, a Shack-Hartmann measuring device (wavefront measuring device) is used. However, other measuring means such as a stylus measuring device or a pattern projection method may be used for measuring partial area data. However, when the data format differs due to different measurement means, it is necessary to align the data format of the deformation amount G with the data format.

  By these methods, even when there is deformation due to its own weight, stitching can be performed relatively easily with high accuracy.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  The present invention can be applied to the use of measuring the shape and wavefront of an object to be measured.

3 ... interferometer (measuring means), 12 ... calculating means, 16 ... simulator (acquiring means)

Claims (12)

A measuring method for measuring the shape of an object to be measured,
Measuring the shape information of the object to be measured in different inclination states for each of a plurality of partial regions set by dividing the object to be measured;
Obtaining deformation information due to gravity in a corresponding inclined state for each partial region of the object to be measured;
Subtracting the deformation amount information obtained by the obtaining step from the shape information measured by the measuring step for each partial region;
Connecting the shape information of the plurality of partial regions obtained by the subtracting step;
A measuring method characterized by comprising: The shape information of the measurement object is a shape of the measurement object,
Step, measuring method according to claim 1, the deformation amount of the partial regions, and obtains by simulation from the design value of the object to be measured to obtain the deformation amount information. The shape information of the measurement object is a shape of the measurement object,
Step characterized by obtaining by measuring the samples with a deformation amount of the partial regions, the materials and shapes which can be regarded as the object to be measured or the object to be measured to obtain the deformation amount information The measurement method according to claim 1. The shape information of the device under test is an inclination of a wavefront of light from the device under test,
The step of acquiring the deformation amount information includes acquiring, as a deformation amount information of each partial region, a slope corresponding to the slope of the wavefront from a design value of the object to be measured by simulation. The measuring method described. The shape information of the device under test is an inclination of a wavefront of light from the device under test,
The step of acquiring the deformation amount information is obtained by actually measuring a sample that can be regarded as the measurement object or the measurement object with an inclination corresponding to the inclination of the wavefront as the deformation amount information of each partial region. The measurement method according to claim 1, wherein the measurement method is acquired. The shape of the object to be measured in weightlessness is rotationally symmetric with respect to an axis, and a plurality of holding portions for holding the object to be measured are disposed rotationally symmetrically with respect to the axis, and the object to be measured is 360 ° with respect to the axis. When the partial region overlaps n times during rotation, and the holding unit overlaps by an integral multiple of n while the object to be measured rotates 360 ° with respect to the axis, the step of acquiring the deformation amount information includes: the deformation amount information of the partial regions, in any one of claims 1 to 5 depends on the tilt angle of the shaft, characterized in that the rotation angle about previous SL-axis as a function that is independent The measuring method described.   The measurement method according to claim 6, wherein the function is defined by fitting with respect to an inclination angle of the axis. Obtaining the deformation amount information, the deformation amount information of the partial regions, characterized in that expressed as a function that depends the on the rotation angle of the shaft about the inclination angle of the axis is set to the object to be measured The measurement method according to any one of claims 1 to 5.   The measurement method according to claim 8, wherein the function is defined by fitting with respect to each of an inclination angle of the axis and a rotation angle around the axis. A measuring device for measuring the shape of an object to be measured,
Measuring means for measuring the shape information of the object to be measured in different inclination states for each of a plurality of partial regions set by dividing the object to be measured;
Acquisition means for acquiring deformation amount information due to gravity in a corresponding inclined state for each partial region of the object to be measured;
An operation for subtracting the deformation amount information acquired by the acquisition unit from the shape information measured by the measurement unit for each partial region, and connecting the shape information of the plurality of partial regions obtained by subtraction. Means,
A measuring apparatus comprising:   The measuring apparatus according to claim 10, wherein the measuring unit is an interferometer. It said measuring means Ri wavefront measuring instrument der for measuring the slope of the wavefront of the light from the object to be measured,
The acquisition unit measuring apparatus according to claim 10, characterized that you get the inclination corresponding to the inclination of the wave front as the deformation amount information.