JP6210832B2 - Measuring method and measuring device - Google Patents

Description

  The present invention relates to a measurement method and a measurement apparatus used for measuring the surface shape of a test object using light.

  In recent years, aspherical optical elements are frequently used in optical devices such as cameras, optical drives, and exposure apparatuses, and as the accuracy of these optical devices increases, the shape of the aspherical optical elements also needs to be increased. Yes. In order to realize such a highly accurate shape of the aspherical optical element, it is necessary to measure the shape of the aspherical optical element with high precision, and measurement using a Shack-Hartmann sensor as one of the measuring devices for that purpose An apparatus has been proposed (see Patent Document 1).

  As shown in the schematic configuration of FIG. 10, when measuring the shape of the test object 120 such as an aspherical optical element by the measuring device 100, the test object 120 is arranged at the test position. The light source light emitted from the light source 103 is reflected by the beam splitter 104, passes through the objective lens 102, passes through the aperture 110, and is irradiated to the entire surface to be inspected 120a with the same curvature. The reflected light from the surface 120a to be inspected passes through the objective lens 102 and the beam splitter 104, enters the Shack-Hartmann sensor 105, enters each microlens of the microlens array 106, and spots on the CCD camera 107 respectively. Form. An image photographed by the CCD camera 107 is input to a computer 109 via a frame grabber 108, and a spot position distribution (hereinafter referred to as spot distribution) on the CCD camera 107 is calculated based on this image.

  The computer 109 compares the measured spot distribution with a reference spot distribution acquired in advance using a spherical wave that is a reference, and calculates the amount of movement of each spot. One spot movement amount is the difference between the inclination of the area of the inspection target surface 120a collected by one microlens and the inclination of the reference spherical wave. By integrating over all the microlenses, the amount of movement to the reference spherical surface is obtained. The shape error of the inspection surface 120a can be obtained.

US Pat. No. 6,750,958

  However, the measuring apparatus 100 described in Patent Document 1 can acquire the data of the optical axis position with respect to the outer peripheral portion of the test object 120, although the data of the optical axis position with respect to the measured surface 120a can be acquired. Can not. Here, the outer peripheral portion is a portion that can be positioned, for example, attached to another member at a portion other than the inspection surface 120a of the inspection object 120. That is, since there is no information on the outer periphery of the test object 120 within the visual field of the Shack-Hartmann sensor 105, it is difficult to calculate the positional relationship between the outer periphery of the test object 120 and the test surface 120a with high accuracy. is there. Here, if the representative point for defining the position of the surface 120a to be inspected is the optical axis, the positional relationship between the outer periphery of the object 120 and the surface 120a to be inspected is the outer periphery of the object 120 and the optical axis. And the positional relationship.

  Even if the outer periphery of the test object 120 is placed within the field of view of the Shack-Hartmann sensor 105, the resolution is limited by the lens pitch of the microlens array 106, so the position of the outer periphery of the test object 120 and the optical axis. It is difficult to calculate the relationship with high accuracy. For this reason, in the case of assembling the test object 120 after measurement to a lens barrel, for example, the positional relationship between the outer peripheral portion of the test object 120 and the optical axis cannot be determined with high accuracy, and desired optical performance cannot be exhibited. There was a possibility.

  An object of this invention is to provide the measuring method and measuring apparatus which can measure the positional relationship of the outer peripheral part of a test object and an optical axis with high precision.

The present invention includes a light source, a sheet catcher click Hartmann sensor, a measuring optical system, an arithmetic unit, a shape measuring apparatus comprising, in the measurement method of measuring the test object, the arithmetic unit, the test object the positions of a plurality of light spots measured from the reflected light of the projected light by the Shack-Hartmann sensor to an acquisition process for acquiring a position of the plurality of light spots as the measured position data, already known A reference position data that is a position of a plurality of light spots formed by a reference object having a reference surface having a shape and an outer peripheral portion around the reference surface and having a known positional relationship between the outer peripheral portion and the optical axis; based on said test position data, the first measurement step and, prior Symbol reference position data and the test position data measured by calculating the position of the outer peripheral portion of the test object with respect to the optical axis of the test object based on the test Characterized by a second measuring step of measuring by calculating the shape of the test surface of the execution.

Further, the present invention includes a light source, a sheet catcher click Hartmann sensor, comprising: a measuring optical system, a calculation unit, and the shape measuring apparatus for measuring a test object, the arithmetic unit, the test object reference plane the positions of a plurality of light spots is measured by the Shack-Hartmann sensor the reflected light projected light, it acquires the positions of the plurality of light spots as the measured position data, having a known shape for And reference position data which are positions of a plurality of light spots formed by a reference object having a known positional relationship between the outer periphery and the optical axis. And measuring the position of the outer periphery of the test object with respect to the optical axis of the test object, and based on the reference position data and the test position data, the test surface of the test object Measure by calculating the shape It is characterized in.

  According to the present invention, based on the reference position data and the test position data, the position of the outer periphery of the test object with respect to the optical axis of the test object is measured, and the shape of the test surface is measured. That is, the position of the outer peripheral portion of the test object and the shape of the test surface are measured based on the reference position data regarding the reference object whose positional relationship with the Shack-Hartmann sensor is known. As a result, the positional relationship between the outer peripheral portion of the test object and the optical axis can be measured with high accuracy.

It is explanatory drawing which shows schematic structure of the measuring device which concerns on 1st Embodiment of this invention. It is a flowchart which shows the process sequence at the time of calculating a test object positional relationship with the measuring device which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the process sequence at the time of calculating test object positional relationship with the measuring device which concerns on 1st Embodiment of this invention, (a) is the state which installed the reference object, (b) is the 1st difference. It is the state which calculated. Further, (c) shows a state where the test object is installed and the second difference is calculated, and (d) shows a state where the relative positional relationship between the optical axes is calculated. It is a flowchart which shows the process sequence at the time of calculating a test object positional relationship with the measuring apparatus which concerns on 2nd Embodiment of this invention. It is explanatory drawing which shows the process sequence at the time of calculating a test object positional relationship with the measuring device which concerns on 2nd Embodiment of this invention, (a) is the state which calculated the coordinate of the reference | standard object optical axis, (b) is This is a state where the coordinates of the optical axis of the test object and the relative positional relationship between the optical axes are calculated. It is a flowchart which shows the process sequence at the time of calculating a test object positional relationship with the measuring apparatus which concerns on 3rd Embodiment of this invention. It is explanatory drawing which shows the process sequence at the time of calculating test object positional relationship with the measuring device which concerns on 3rd Embodiment of this invention, (a) is the state which installed the reference | standard thing and calculated the 1st difference, ( b) shows a state in which the optical axis of the reference object coincides with the optical axis of the measurement optical system. Further, (c) shows a state in which the test object is installed and the second difference is calculated, and (d) shows a state in which the test object optical axis is matched with the optical axis of the measurement optical system. It is explanatory drawing which shows schematic structure of the measuring device which concerns on 4th Embodiment of this invention, (a) is a whole schematic block diagram, (b) is an enlarged view of an X-axis sensor and a Y-axis sensor. It is explanatory drawing which shows the modification of the test object and reference | standard object which are used with the measuring device of this invention, (a) is a diameter reduction part of a disc part, and (b) is an internal peripheral surface of a recessed part. Is the outer periphery, and (c) is an arc shape as a whole. It is explanatory drawing which shows schematic structure in the case of measuring to-be-inspected surface with the conventional measuring device.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, a measuring apparatus 1 includes a light source unit 10 for emitting measurement laser diode light as light source light, and a beam splitter (separation optical system) into which the light source light from the light source unit 10 is incident. 20. In addition, the measuring apparatus 1 includes a holding unit 30 that positions and places an object to be measured (optical element) 2 and a reference object 3 that are measurement objects at a measurement position, and measurement light reflected by the measurement object is a beam. And a Shack-Hartmann sensor 40 that is incident through the splitter 20. In the present embodiment, the test object 2 and the reference object 3 are aspherical lenses or aspherical mirrors whose overall shape is a substantially disk shape and whose test surface 2a or reference surface 3a is convex.

  The light source unit 10 is provided with a light source 11 that emits laser diode light (light) that is light source light. The laser light emitted from the light source 11 is emitted by the collimator lens 12 with a waveform of a plane wave. It is like that. Here, the light source 11 is a laser diode light source, but is not limited thereto, and a white light source, a laser light source, or the like may be used. The configuration of the light source unit 10 is merely an example, and is not limited to this. For example, an optical fiber may be interposed between the light source 11 and the collimator lens 12.

  The beam splitter 20 includes an incident surface 21 facing the light source unit 10, an entrance / exit surface 22 facing the measurement object, and an exit surface 23 facing the Shack-Hartmann sensor 40. The beam splitter 20 emits the light source light incident on the incident surface 21 from the entrance / exit surface 22 and irradiates the measurement object, and the reflected light reflected by the measurement object enters the entrance / exit surface 22 as measurement light. However, it is separated from the light source light and emitted from the emission surface 23.

  An objective lens 24 is provided opposite to the entrance / exit surface 22 of the beam splitter 20. In the present embodiment, since the inspection surface 2a or the reference surface 3a is convex, the objective lens 24 is a condenser lens. As a result, the objective lens 24 irradiates the measurement object with the light source light emitted from the entrance / exit surface 22 of the beam splitter 20 as a spherical wave and makes the measurement light reflected by the measurement object enter the entrance / exit surface 22. It is supposed to be. Note that when the test object 2 and the reference object 3 are concave, the objective lens 24 can be a diverging lens.

  The holding unit 30 includes a holder (installation unit) 31 that detachably holds the measurement object at the measurement position, and the holder 31 is relatively positioned with respect to the measurement optical system 60 in order to adjust the position and orientation of the holder 31. A movable moving stage (moving mechanism) 32 is provided. For example, the holder 31 is fixed when the measurement object comes into contact with the X-axis direction and the Y-axis direction of the horizontal plane. Here, the holding unit 30 includes the moving stage 32, but in the present embodiment, the holder 31 is used while being fixed as described later, and therefore the moving stage 32 may not be included.

  At least one of the test object 2 and the reference object 3 can be selectively attached to and detached from the holder 31 as a measurement object. The test object 2 includes an axial target aspheric test surface 2 a having a test object optical axis 2 c and an edge (outer peripheral part) 2 b that can be positioned with respect to the holder 31. In the present embodiment, the edge 2b is an outer surface and is positioned in the X-axis direction and the Y-axis direction by directly contacting the holder 31. Further, for example, a marking line is used for positioning in the rotation direction around the Z axis (optical axis). Alternatively, an orientation flat surface (plane) may be provided on the outer periphery of the test object 2 with respect to the rotation direction around the Z axis.

  The reference object 3 includes a reference aspherical reference surface 3a having a reference object optical axis 3c, and an edge (outer peripheral part) 3b that can be positioned with respect to the holder 31, and a reference object optical axis 3c and an edge 3b. The reference object positional relationship is known. That is, the reference object 3 includes a reference surface 3a having a known shape and an edge 3b around the reference surface 3a, and the positional relationship between the edge 3b and the reference object optical axis 3c is known as the reference object position relationship. It is supposed to be.

  This reference object positional relationship is acquired in advance by using another measuring device. The edge 3 b is positioned in the X-axis direction and the Y-axis direction by directly contacting the holder 31. Further, for example, a marking line is used for positioning in the rotation direction about the Z axis. Or you may make it position by providing an orientation flat surface in the outer periphery of the reference | standard thing 3 with respect to the rotation direction centering on a Z-axis. For example, as shown in FIG. 3A, the reference object positional relationship is set such that the distance between the reference object optical axis 3c and the edge 3b in the X-axis direction is Rx, and the distance in the Y-axis direction is Ry. .

  The reference surface 3a is known not only in the position of the reference object optical axis 3c but also in the shape of the reference surface 3a. Thereby, as will be described later, the shape of the surface 2a to be inspected can be obtained by calculating the difference in shape between the reference surface 3a and the surface 2a to be inspected. In addition, although the design value of the reference object 3 may be used for the shape of the reference surface 3a, the reference surface 3a of the reference object 3 is measured, and the data obtained by the measurement is set as the shape of the reference surface 3a. Also good.

  Here, in FIG. 1, since the inspection surface 2 a and the reference surface 3 a are convex, the inspection object 2 and the reference object 3 are installed in a range closer to the objective lens 24 than its focal point. This is not a limitation. For example, if the inspection surface 2a and the reference surface 3a are concave, the inspection object 2 and the reference object 3 are installed in a range farther from the focal point than the objective lens 24.

  The measurement light reflected by the surface 2a to be inspected or the reference surface 3a enters from the entrance / exit surface 22 of the beam splitter 20, is reflected within the beam splitter 20, exits from the exit surface 23, and enters the Shack-Hartmann sensor 40. It has become.

  The beam splitter 20 here does not consider polarization, but the beam splitter 20 may be a polarization beam splitter and light incident on the beam splitter 20 may be linearly polarized light. In this case, the polarization direction of the light incident on the polarization beam splitter is set to the direction of transmission through the polarization beam splitter, and a quarter wavelength plate is disposed between the change beam splitter and the objective lens 24. The polarization azimuth of the measurement light reflected from the surface 2a to be inspected or the reference surface 3a passes through the quarter-wave plate twice, so that it rotates 90 degrees with the incident light, and all of the measurement light is reflected by the polarization beam splitter. Since the light is incident on the Shack-Hartmann sensor 40, the utilization efficiency of the measurement light can be improved.

  The Shack-Hartmann sensor 40 includes a microlens array 41 that divides and collects incident light rays to form spots, and a CCD camera (two-dimensional sensor) 42 that images a plurality of formed spots. Yes. The Shack-Hartmann sensor divides and condenses the wavefront of incident light by a microlens array 41 and detects it as an array of a plurality of spots by a CCD camera 42.

  The microlens array 41 has a plurality of microlenses that each collect light on one image plane. However, the number of pixels of the CCD camera 42 is larger than the total number of microlenses of the microlens array 41. The CCD camera 42 is disposed on the image plane of the microlens array 41. Here, the CCD camera 42 is used as the image sensor, but the present invention is not limited to this, and another camera may be used.

  If the wavefront of the measurement light incident on the Shack-Hartmann sensor 40 is a plane wave, the position of the formed spot is on each optical axis of each microlens. The inspected surface 2a or the reference surface 3a and the microlens array 41 are arranged in a conjugate manner, and each microlens corresponds to a region of the inspected surface 2a or the reference surface 3a.

  The Shack-Hartmann sensor 40 described above is connected to the calculation unit 50 via a frame grabber 55. The calculation unit 50 is configured by a computer, for example, and calculates the positional relationship between the test object optical axis 2c and the edge 2b by performing a calculation based on the measurement value acquired from the Shack-Hartmann sensor 40. A computer constituting the calculation unit 50 includes, for example, a CPU 51, a RAM 52 that temporarily stores various data, a ROM 53 that stores programs for executing various calculations, an input / output interface circuit (I / F) 54, It has.

  The CPU 51 obtains the light intensity centroid of each light spot based on the image obtained by the CCD camera 42 of the Shack-Hartmann sensor 40, calculates the position of the light spot, obtains the spot distribution, and stores the result in the RAM 52. It is supposed to be. Further, the CPU 51 calculates the shape of the test object 2 and the positional relationship between the test object optical axis 2c and the edge 2b based on data such as the spot distribution.

  As a procedure for calculating the shape of the test object 2, a reference spot distribution is acquired in advance as calibration data (reference position data) using the reference object 3. If there is a difference from the reference surface 3a in one area of the surface 2a to be inspected, the spot position of the microlens corresponding to the one area is shifted from the reference position depending on the average value of the difference in the one area. become. The spot position on the reference surface 3a is compared with the spot position on the surface 2a to be inspected, and the wavefront aberration of the measurement light is obtained to calculate the shape error of the surface 2a to be inspected with respect to the reference surface 3a. Since one spot movement amount is the difference between the inclination of the region of the surface 2a to be inspected and the inclination of the reference surface 3a collected by one microlens, the surface 2a to be inspected is integrated over all the microlenses. The shape error from the entire reference surface 3a can be obtained.

  The procedure of the measuring method for calculating the positional relationship between the test object optical axis 2c and the edge 2b of the test object 2 by the measuring apparatus 1 described above will be described with reference to the flowchart shown in FIG. 2 and the explanatory diagram shown in FIG. .

  First, as shown in FIG. 3A, the edge 3b of the reference object 3 is placed in contact with the holder 31 (step S1 in FIG. 2). At this time, the installation angle of the reference object 3 in the rotation direction around the reference object optical axis 3c is determined by using the marking line, and the X-axis direction radius Rx and the Y-axis direction radius which are reference object position relationships. Ry is appropriately positioned with respect to the holder 31.

  Then, the shape of the reference surface 3a of the reference object 3 is measured by the measuring device 1 (step S2 in FIG. 2). As shown in FIG. 3B, the CPU 51 uses the technique of using a Zernike function described later based on the measurement result to determine the difference (first difference) between the reference object optical axis 3c and the optical axis 60a of the measurement optical system 60. ) Is calculated (step S3 in FIG. 2). Here, the CPU 51 calculates the difference ΔX1 in the X-axis direction and the difference ΔY1 in the Y-axis direction as the first difference.

  Then, the reference object 3 is detached from the holder 31 (step S4 in FIG. 2), and the edge 2b of the test object 2 is placed in contact with the holder 31 as shown in FIG. 3C (step in FIG. 2). S5). At this time, the installation angle of the rotation direction of the test object 2 around the test object optical axis 2c is set using the marking line so that the test object 2 and the reference object 3 are installed at the same position. To do. Here, the holder 31 is used in a fixed state by fixing the moving stage 32.

  And the shape of the to-be-inspected surface 2a of the to-be-tested object 2 is measured with the measuring device 1 (step S6 of FIG. 2, acquisition process). That is, the CPU 51 projects light emitted from the light source 11 onto the test object 2 by the measurement optical system 60, and uses the Shack-Hartmann sensor 40 to determine the positions of a plurality of light spots from the reflected light of the projected light. Measurement is performed, and the positions of a plurality of light spots are acquired as test position data. As shown in FIG. 3 (c), the CPU 51 uses the method of using the Zernike function based on the measurement result to make a difference (second difference) between the test object optical axis 2c and the optical axis 60a of the measurement optical system 60. Is calculated (step S7 in FIG. 2). Here, the CPU 51 calculates the difference ΔX2 in the X-axis direction and the difference ΔY2 in the Y-axis direction as the second difference.

  Furthermore, as shown in FIG. 3D, the CPU 51 determines the difference (optical axis) between the position of the reference object optical axis 3c and the position of the test object optical axis 2c based on the first difference and the second difference. The relative positional relationship between them is calculated (step S8 in FIG. 2). Here, the CPU 51 calculates the difference ΔX = | ΔX1−ΔX2 | in the X axis direction and the difference ΔY = | ΔY1−ΔY2 | in the Y axis direction as the relative positional relationship between the optical axes.

  The CPU 51 calculates a test object positional relationship, which is a positional relationship between the test object optical axis 2c and the edge 2b, based on the relative positional relationship (ΔX, ΔY) between the optical axes and the reference object positional relationship (step). S9, first measurement step). Here, the CPU 51 acquires the object positional relationship by adding or subtracting the difference ΔX in the X-axis direction and the difference ΔY1 in the Y-axis direction to the radii Rx and Ry that are the reference object positional relationship. Can do. The addition / subtraction selection here is determined depending on, for example, whether the difference is in the direction in which the difference is added to the radii Rx and Ry, which is the reference object position relationship, or in the direction in which the difference is subtracted. That is, the CPU 51 calculates the position of the edge 2b of the test object 2 with respect to the test object optical axis 2c based on the reference position data and the test position data that are positions of a plurality of light spots formed by the reference object 3. To measure.

  And CPU51 measures by calculating the shape of to-be-inspected surface 2a based on reference | standard position data and to-be-tested position data (step S10 of FIG. 2, 2nd measurement process).

  After the measurement of the position of the test object optical axis 2c and the shape of the test surface 2a is completed, the next test object 2 is set in the holder 31 using the data of the reference surface 3a of the reference object 3. The position of the next test object optical axis 2c and the shape of the test surface 2a can be measured. That is, since the measurement process can be started for the next test object 2 from step S5 in FIG. 2, the measurement time can be shortened compared to the case of measuring the reference object 3.

  In the above-described procedure, the difference between the reference object optical axis 3c and the optical axis 60a of the measurement optical system 60 and the difference between the test object optical axis 2c and the optical axis 60a of the measurement optical system 60 are respectively calculated. The object positional relationship is calculated using the difference between the differences, but is not limited to this. For example, since the reference object positional relationship between the reference object optical axis 3c and the edge 3b is known, the position between the optical axis 60a of the measurement optical system 60 and the edge 3b (holder 31) from the first difference calculated in step S3. The relationship can be calculated. Thereby, since the positional relationship between the optical axis 60a of the measurement optical system 60 and the holder 31 is known, the object to be detected between the optical axis 2c of the test object and the edge 2b (holder 31) is calculated from the second difference calculated in step S7. The inspection position relationship may be calculated. In this case, although it differs from the above-described procedure in that the optical axis 60a of the measurement optical system 60 is calculated, the first difference and the second difference are calculated, and as a result, the difference between the differences is used. The same principle is used.

  Moreover, when manufacturing the test object 2 mentioned above, it molds first (molding process), and the shape of the test object 2 is measured by the measuring method mentioned above, and the molded test object 2 is evaluated ( Evaluation process). As a result, the test object 2 having a highly accurate shape can be obtained.

  Hereinafter, a specific example of the process of calculating the first difference and the second difference in step S3 and step S7 will be described in detail. Here, it is assumed that the information of the measurement light detected by the Shack-Hartmann sensor 40 is analyzed by the CPU 51 and fitted to the Zernike function. In an axisymmetric aspherical surface, the second and third terms (tilt term) when fitted to the Zernike function indicate the inclination of the reference surface 3a or the surface to be inspected 2a with respect to the spherical wave irradiated on the reference surface 3a or the surface to be inspected 2a. , 8 (frame term) indicates a shift in a direction perpendicular to the optical axis direction. In the following, the case where the surface 2a to be inspected is measured will be described for the sake of explanation, but the same applies to the case where the reference surface 3a is measured.

When the design shape of the surface 2a to be inspected is an axisymmetric aspherical surface f ₀ (r), the shape is developed as in Equation 1 using a Zernike function.

  Here, r is expressed as Equation 2 in the XY coordinates.

In Equation 1, r ₀ represents an evaluation radius of the surface 2a to be inspected, and Z _k2 (x, y) represents an axially symmetric component of the Zernike function.

Next, consider a case where the optical axis 2c of the test object is arranged so as to be shifted in the X-axis direction by a minute amount Δx with respect to the optical axis (irradiation spherical wave optical axis) 60a of the measurement optical system 60. The shape f _{xs, Δx} (x, y) at this time is approximated as Equation 3.

The derivative included in the second term on the right side of Equation 3 can be expanded as Equation 4 by the Zernike function f _i (x, y).

In Equation 4, Z ₂ (x, y) and Z ₇ (x, y) are functions defined by Equation 5 of the Zernike function, and represent a tilt component and a coma component, respectively.

  Equations 3 to 5 show the case where the optical axis 2c of the test object is arranged so as to be shifted in the X-axis direction by a minute amount Δx with respect to the optical axis 60a of the measurement optical system 60. Similarly, the case where they are arranged so as to be displaced in the direction is also expressed as Equation 6.

When the test object optical axis 2 c is rotated by a minute amount θ _x around the X axis with respect to the optical axis 60 a of the measurement optical system 60, the shape f _{xt, θx} (x, y) is expressed by Equation 7: It is expressed in

When obtaining Δf _xt (x, y), an appropriate minute amount θ _x is set and a simultaneous equation shown in Expression 8 is created.

F _{xt, θx} (x, y) is obtained from the simultaneous equations shown in Expression 8 and substituted into Expression 9.

This Δf _xt (x, y) can be expanded as shown in Equation 10 using a Zernike function.

Equation 7-10 is the test object optical axis 2c is a case which is rotating about the X axis with respect to the optical axis 60a of the measuring optical system 60 by a small amount theta _x, very small amount around the Y axis Similarly, in the case of rotating by θy, it can be developed as shown in Equation 11.

Therefore, the optical axis 2c of the test object moves by Δx in the X-axis direction and Δy in the Y-axis direction with respect to the optical axis 60a of the measurement optical system 60, and rotated by θx about the X axis and θy about the Y axis. The shape of the surface to be inspected f _{Δx, Δy, θx, θy} (x, y) at the time can be expressed by Equation 12.

Further, the non-axisymmetric component W _{r, as} (x, y) of the reflected wavefront is expressed by Equation 13.

Since the non-axisymmetric component of the reflected wavefront is transmitted to the Shack-Hartmann sensor 40 through the measurement optical system 60 at the magnification a, the wavefront W _{s, as} (x , Y) is as shown in Equation 14.

Here, the wavefront W _s (x, y) obtained by the Shack-Hartmann sensor 40 can be decomposed into a Zernike function as shown in Equation 15.

The obtained c _{s, 2} , c _{s, 3} , c _{s, 7} , c _{s, 8} have the relationship of Equation 16 with respect to Δx, Δy, θx, θy.

  By solving the simultaneous equations shown in Expression 16, Δx, Δy, θx, θy can be calculated, and the optical axis deviation of the optical axis 2c of the test object with respect to the optical axis 60a of the irradiating measurement optical system 60 is obtained. be able to.

  As described above, according to the measurement apparatus 1 of the present embodiment, the position of the edge 2b of the test object 2 with respect to the test object optical axis 2c is measured based on the reference position data and the test position data, and the test is performed. The shape of the surface 2a is measured. That is, the position of the edge 2b of the test object 2 and the shape of the test surface 2a are measured based on the reference position data regarding the reference object 3 whose positional relationship with the Shack-Hartmann sensor 40 is known. Thereby, the positional relationship between the edge 2b of the test object 2 and the test object optical axis 2c can be measured with high accuracy.

  Further, according to the measurement apparatus 1 of the present embodiment, the first difference and the second difference, or the optical axis 60a of the measurement optical system 60 as necessary from the reference surface 3a or the reflected wavefront of the surface to be inspected 2a. For example, it can be calculated with high accuracy of 1 μm or less. For this reason, the object positional relationship between the edge 2b of the object 2 and the object optical axis 2c can be measured with high accuracy.

  Further, according to the measuring apparatus 1 of the present embodiment, the shape of the inspection surface 2a is measured simultaneously with the measurement of the positional relationship between the edge 2b of the inspection object 2 and the optical axis 2c of the inspection object. As a result, since both the shape of the inspection surface 2a and the positional relationship of the optical axis 2c of the test object with respect to the edge 2b can be acquired in one measurement operation, the positional relationship of the test object without increasing the work man-hours of the operator You will be able to get

  In the present embodiment described above, attention has been paid to the Zernike functions 2, 3, 7, and 8 as functions representing the tilt component and the coma component, and the case where the magnitude of the difference between the test object optical axes 2c has been described. This is not a limitation. For example, the coma component may be obtained by paying attention to a higher-order Zernike function having a high spatial frequency.

In this embodiment, the case where the design shape is used has been described. However, the present invention is not limited to this, and the design shape may be obtained without using the design shape. In this case, for example, this sets up the test object 2 and calculates c _{s, 2} , c _{s, 7} from the wavefront incident on the Shack-Hartmann sensor 40. Next, the surface to be inspected 2a is moved by a minute amount Δx in the X-axis direction, and the amount of change Δc _{s, 2} (Δx), Δc _{s, 7} (Δx) of each Zernike coefficient is obtained. Since this change amount has a relation of b ₁₁ and b ₂₁ and Expression 17, b ₁₁ and b ₂₁ can be calculated by this.

Further, the surface to be inspected 2a is rotated by a minute amount θx around the X axis, and the amount of change Δc _{s, 2} (θx), Δc _{s, 7} (θx) of the Zernike coefficient before and after that is obtained. Since this change amount has a relationship of b ₁₂ and b ₂₂ and Expression 18, b ₁₂ and b ₂₂ can be calculated by this.

Note that b ₃₃ , b ₃₄ , b ₄₃ , and b ₄₄ can be calculated by the same method.

In the present embodiment, the wavefront data obtained by the Shack-Hartmann sensor 40 is used as it is. However, the present invention is not limited to this. For example, the wavefront data is once converted into a shape and then the optical axis The difference may be calculated. In this case, the test object 2 is installed, the wave front is measured by the Shack-Hartmann sensor 40, and then the wave front W _s (x, y) is converted into the shape f (x, y). The obtained shape f (x, y) is fitted by Equation 19 using Δx, Δy, θx, θy as fitting parameters.

Δf _xt (x, y) and Δf _yt (x, y) are obtained in advance by the method described above. By calculating Δx, Δy, θx, θy by such fitting, it is possible to obtain the amount of deviation of the optical axis 2c of the test object.

[Second Embodiment]
Next, the measuring device 1 according to the second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in the processing in the CPU 51, but the apparatus itself is the same. Therefore, the same reference numerals are used in FIG. The reference object 3 and the test object 2 are the same as those in the first embodiment.

  The procedure for calculating the positional relationship between the test object optical axis 2c and the edge 2b of the test object 2 in this embodiment will be described with reference to the flowchart shown in FIG. 4 and the explanatory diagram shown in FIG.

  First, as shown in FIG. 5A, the edge 3b of the reference object 3 is placed in contact with the holder 31 (step S11 in FIG. 4). At this time, the installation angle of the reference object 3 in the rotation direction around the reference object optical axis 3c is determined by using the marking line, and the X-axis direction radius Rx and the Y-axis direction radius which are reference object position relationships. Ry is appropriately positioned with respect to the holder 31.

  Then, the shape of the reference surface 3a of the reference object 3 is measured by the measuring device 1 (step S12 in FIG. 4), and the CPU 51 calculates the position of the reference object optical axis 3c in the captured image 43 and coordinates (X1, Y1). Is acquired (step S13 in FIG. 4).

  Then, the reference object 3 is detached from the holder 31 (step S14 in FIG. 4), and the edge 2b of the test object 2 is placed in contact with the holder 31 as shown in FIG. 5B (step in FIG. 4). S15). At this time, the installation angle of the rotation direction of the test object 2 around the test object optical axis 2c is set using the marking line so that the test object 2 and the reference object 3 are installed at the same position. To do. Here, the movable stage 32 is fixed and the holder 31 is fixed.

  And the shape of the to-be-inspected surface 2a of the to-be-tested object 2 is measured with the measuring apparatus 1 (step S16 of FIG. 4, acquisition process). The CPU 51 calculates the position of the test object optical axis 2c in the captured image 43 and acquires the coordinates (X2, Y2) (step S17 in FIG. 4).

  Further, the CPU 51 determines the relative positional relationship between the optical axes of the position of the reference object optical axis 3c and the position of the test object optical axis 2c based on the positions of the reference object optical axis 3c and the test object optical axis 2c. Calculation is performed (step S18 in FIG. 4). Here, the CPU 51 calculates the difference ΔX = | X1-X2 | in the X-axis direction and the difference ΔY = | Y1-Y2 | in the Y-axis direction as the relative positional relationship between the optical axes.

  The CPU 51 calculates the object positional relationship, which is the positional relationship between the object optical axis 2c and the edge 2b, based on the relative positional relationship (ΔX, ΔY) between the optical axes and the reference object positional relationship (step S19). , First measurement step). Here, the CPU 51 acquires the object positional relationship by adding or subtracting the difference ΔX in the X-axis direction and the difference ΔY in the Y-axis direction to the radii Rx and Ry that are the reference object positional relationship. Can do. The addition / subtraction selection here is determined depending on, for example, whether the difference is in the direction in which the difference is added to the radii Rx and Ry, which is the reference object position relationship, or in the direction in which the difference is subtracted.

  And CPU51 measures by calculating the shape of to-be-inspected surface 2a based on reference | standard position data and to-be-tested position data (step S20 of FIG. 4, 2nd measurement process).

  As described above, according to the measuring apparatus 1 of the present embodiment, the relative positional relationship between the optical axes is calculated based on the positions of the reference object optical axis 3c and the test object optical axis 2c. The calculation can be simplified as compared with the case where the optical axis 60a of the measurement optical system 60 is considered using

[Third Embodiment]
Next, a measuring apparatus 1 according to the third embodiment of the present invention will be described. The third embodiment is different from the first embodiment in the processing in the CPU 51, but the apparatus itself is the same. Therefore, FIG. 1 is used in the same way as in the first embodiment, and the description is omitted. The reference object 3 and the test object 2 are the same as those in the first embodiment.

  The procedure for calculating the positional relationship between the test object optical axis 2c and the edge 2b of the test object 2 in this embodiment will be described with reference to the flowchart shown in FIG. 6 and the explanatory diagram shown in FIG.

  First, as shown in FIG. 7A, the edge 3b of the reference object 3 is placed in contact with the holder 31 (step S21 in FIG. 6). At this time, the installation angle of the reference object 3 in the rotation direction around the reference object optical axis 3c is determined by using the marking line, and the X-axis direction radius Rx and the Y-axis direction radius which are reference object position relationships. Ry is appropriately positioned with respect to the holder 31 (not shown). Further, the coordinates of the holder 31 are set on the moving stage 32, and the coordinates of the appropriate position 31a of the holder 31 at the initial time are set as the initial position (0, 0).

  Then, the shape of the reference surface 3a of the reference object 3 is measured by the measuring device 1 (step S22 in FIG. 6), and the CPU 51 uses the Zernike function to detect the reference object optical axis 3c and the optical axis of the measurement optical system 60. The difference (first difference) from 60a is calculated (step S23 in FIG. 6). Here, the CPU 51 calculates the difference ΔX1 in the X-axis direction and the difference ΔY1 in the Y-axis direction as the first difference.

  The CPU 51 determines whether or not the reference object optical axis 3c and the optical axis 60a of the measurement optical system 60 match. Specifically, the CPU 51 determines whether or not the first difference (ΔX1, ΔY1) is equal to or less than a predetermined threshold (specified amount) (step S24 in FIG. 6). The specified amount here can be appropriately set according to the accuracy required for the positional relationship of the test object. The smaller the specified amount, the higher the reference object optical axis 3c and the optical axis 60a of the measurement optical system 60 are. Since the accuracy can be matched, the measurement accuracy can be improved.

  When the CPU 51 determines that the first difference (ΔX1, ΔY1) is not equal to or less than the specified amount, the moving stage 32 is driven in the direction of decreasing the first difference (ΔX1, ΔY1) via the holder 31. The reference object 3 is moved (step S25 in FIG. 6). Then, the shape of the reference surface 3a of the reference object 3 is again measured by the measuring device 1 (step S22 in FIG. 6).

  Further, as shown in FIG. 7B, when the CPU 51 determines that the first difference (ΔX1, ΔY1) is equal to or less than the specified amount, the position (p1, q1) of the holder 31 is set to the first stage. The position is stored in the RAM 52 (step S26 in FIG. 6). The first stage position (p1, q1) of the holder 31 here is measured by appropriately using a control amount to the moving stage 32 or a position detection sensor of the holder 31, and the position is an initial position (0, 0). ) From the first difference (ΔX1, ΔY1). Further, after the reference object optical axis 3c and the optical axis 60a of the measurement optical system 60 coincide with each other, the shape of the reference surface 3a of the reference object 3 may be measured again by the measuring device 1 as necessary.

  Then, the reference object 3 is detached from the holder 31 (step S27 in FIG. 6), and the edge 2b of the test object 2 is placed in contact with the holder 31 as shown in FIG. 7C (step in FIG. 6). S28). At this time, the installation angle of the rotation direction of the test object 2 around the test object optical axis 2c is set using the marking line so that the test object 2 and the reference object 3 are installed at the same position. To do.

  And the shape of the to-be-inspected surface 2a of the to-be-tested object 2 is measured with the measuring device 1 (step S29 of FIG. 6, acquisition process). The CPU 51 calculates a difference (second difference) between the optical axis 2c of the test object and the optical axis 60a of the measurement optical system 60 by using a Zernike function (step S30 in FIG. 6). Here, the CPU 51 calculates the difference ΔX2 in the X-axis direction and the difference ΔY2 in the Y-axis direction as the second difference.

  The CPU 51 determines whether or not the test object optical axis 2c and the optical axis 60a of the measurement optical system 60 match. Specifically, the CPU 51 determines whether or not the second difference (ΔX2, ΔY2) is equal to or smaller than a predetermined threshold (specified amount) (step S31 in FIG. 6). The specified amount here can be set as appropriate according to the accuracy required for the positional relationship of the test object. The smaller the specified amount, the more the test object optical axis 2c and the optical axis 60a of the measurement optical system 60 are connected. Measurement accuracy can be improved because of high accuracy.

  When the CPU 51 determines that the second difference (ΔX2, ΔY2) is not less than or equal to the specified amount, the moving stage 32 is driven in the direction of decreasing the second difference (ΔX2, ΔY2) via the holder 31. The test object 2 is moved (step S32 in FIG. 6). Then, the shape of the inspection surface 2a of the inspection object 2 is again measured by the measuring device 1 (step S29 in FIG. 6).

  Further, as shown in FIG. 7D, when the CPU 51 determines that the second difference (ΔX2, ΔY2) is equal to or less than the specified amount, the position (p2, q2) of the holder 31 is set to the second stage. The position is stored in the RAM 52 (step S33 in FIG. 6). The second stage position (p2, q2) of the holder 31 here is measured by appropriately using a control amount to the moving stage 32 or a position detection sensor of the holder 31, and the position is the first stage position ( The position is moved by the second difference (ΔX2, ΔY2) from p1, q1). Further, after the optical axis 2c of the test object and the optical axis 60a of the measurement optical system 60 coincide with each other, the shape of the inspection surface 2a of the test object 2 is again measured by the measuring device 1 as necessary. Also good.

  Furthermore, the CPU 51 determines the optical axis between the position of the reference object optical axis 3c and the position of the test object optical axis 2c based on the first stage position (p1, q1) and the second stage position (p2, q2). The relative positional relationship between them is calculated (step S34 in FIG. 6). Here, as the relative positional relationship between the optical axes, the CPU 51 uses the difference ΔX = | p1−p2 | = | ΔX1−ΔX2 | in the X axis direction and the difference ΔY = | q1−q2 | = | ΔY1 in the Y axis direction. -ΔY2 | is calculated.

  The CPU 51 calculates an object position relationship that is a position relationship between the object optical axis 2c and the edge 2b based on the relative position relationship (ΔX, ΔY) between the optical axes and the reference object position relationship (FIG. 6). Step S35, first measurement step). Here, the CPU 51 acquires the object positional relationship by adding or subtracting the difference ΔX in the X-axis direction and the difference ΔY in the Y-axis direction to the radii Rx and Ry that are the reference object positional relationship. Can do. The addition / subtraction selection here is determined depending on, for example, whether the difference is in the direction in which the difference is added to the radii Rx and Ry, which is the reference object position relationship, or the direction in which the difference is subtracted.

  And CPU51 measures by calculating the shape of to-be-inspected surface 2a based on reference | standard position data and to-be-tested position data (step S36 of FIG. 6, 2nd measuring process).

  As described above, according to the measurement apparatus 1 of the present embodiment, the reference object optical axis 3c and the test object optical axis 2c are made to coincide with the optical axis 60a of the measurement optical system 60, and light is transmitted using each stage position. The relative positional relationship between the axes is calculated. Since the influence of alignment is small due to the coincidence of the optical axes, the shape measurement becomes highly accurate, and the accuracy of measuring the relationship between the test object optical axis 2c and the edge 2b can be improved.

  In the first to third embodiments described above, the case where the test object 2 and the reference object 3 are positioned by directly abutting against the holder 31 has been described. However, the present invention is not limited to this. For example, the test object 2 and the reference object 3 may be positioned using a non-contact sensor. In this case, for example, an X-axis sensor 33 that detects the X-axis direction of the test object 2 and the reference object 3, a Y-axis sensor 34 that detects the Y-axis direction, and the apex, as in the measurement apparatus 101 shown in FIG. A Z-axis sensor 35 that detects the position (Z-axis direction) is used. In addition, the test object 2 and the reference object 3 may be provided with planes 2d and 3d facing the X-axis direction and planes 2e and 3e facing the Y-axis direction in order to position the rotation angle in the optical axis direction. preferable. The Z-axis sensor 35 is movable between a measurement position that overlaps the optical path and a retreat position that retracts. The Z-axis sensor 35 is located at the measurement position when the object 2 and the reference object 3 are positioned, and When the object 2 and the reference object 3 are measured, they are positioned at the retreat position.

  In the first to third embodiments described above, the case where the outer surfaces of the test object 2 and the reference object 3 are positioned as the edges 2b and 3b has been described. However, the present invention is not limited to this. For example, as shown in FIG. 9A, when the object 2 (reference object 3) is reduced in diameter on the opposite surface side of the inspection surface 2a (reference surface 3a), the outer periphery of the reduced diameter portion The part can be the edge 2f (3f). In this case, the holder 36 is provided with an abutting portion 36a that abuts only on the edge 2f (3f). For example, as shown in FIG. 9B, when the test object 2 (reference object 3) has a concave central portion on the opposite surface side of the test surface 2a (reference surface 3a), the inner periphery of the recess The surface can be edge 2g (3g) (outer peripheral part). In this case, the holder 37 is provided with an abutting portion 37a that abuts only on the edge 2g (3g).

  In the first to third embodiments described above, the test object 2 and the reference object 3 are described as having a substantially disc shape, but the present invention is not limited to this. That is, even if there is no part of the test object optical axis 2c (reference object optical axis 3c), the test object 2 is measured by measuring a part of the test object 2 (reference object 3) having an aspherical object. It is possible to calculate the position of the optical axis 2c (reference object optical axis 3c). For example, as shown in FIG. 9C, the test object 2 (reference object 3) is formed into an arc shape having an edge 2b (3b) on the circumferential surface, or a shape such as a fan shape or a hole is formed. be able to.

DESCRIPTION OF SYMBOLS 1 ... Measuring apparatus, 2 ... Test object (optical element), 2a ... Test surface, 2b ... Edge (outer peripheral part), 2c ... Test object optical axis (optical axis of test object), 3 ... Reference object, 3a ... reference plane, 3b ... edge (outer peripheral part), 3c ... reference object optical axis (reference object optical axis), 11 ... light source, 20 ... beam splitter, 31 ... holder (installation part), 32 ... moving stage (moving) Mechanism), 40 ... Shack-Hartmann sensor, 41 ... microlens array, 42 ... CCD camera (two-dimensional sensor), 50 ... arithmetic unit, 60 ... measuring optical system, 60a ... optical axis of measuring optical system.

Claims (9)

A light source, a sheet catcher click Hartmann sensor, a measuring optical system, an arithmetic unit, a shape measuring apparatus comprising, in the measurement method of measuring the test object,
The computing unit is
An acquisition step wherein the measuring the position of a plurality of light spots by the Shack-Hartmann sensor from the reflected light of the test object with respect to projected light, acquires the positions of the plurality of light spots as the measured position data ,
Reference position relationship between the outer peripheral portion and the optical axis is the position of a plurality of light spots formed by the reference object are known with and a peripheral portion around the reference surface and the reference surface having a shape of a previously known A first measurement step of measuring by calculating the position of the outer peripheral portion of the test object relative to the optical axis of the test object based on the position data and the test position data;
Based on the previous SL reference position data and the test position data, said performing a second measurement step of measuring by calculating the shape of the test surface of the test object, and
A measuring method characterized by this. In the first measuring step, based on pre-Symbol reference position data, it calculates a first difference which is a difference between the positions of the optical axis of the measuring optical system and the optical axis of the reference product, the test position data And calculating a second difference that is a difference in position between the optical axis of the test object and the optical axis of the measurement optical system, and based on the first difference and the second difference, Calculating the relative positional relationship between each other, and calculating the position of the outer peripheral portion of the test object relative to the optical axis of the test object based on the relationship between the relative positional relationship and the optical axis and outer peripheral portion of the reference object. Measure with
The measuring method according to claim 1. In the first measuring step, based on pre-Symbol reference position data, calculates the position of the optical axis of the reference object, based on said test position data, calculates the position of the optical axis of the test object, wherein Based on the position of the optical axis of the reference object and the position of the optical axis of the test object, the relative positional relationship between the optical axes is calculated, and the relationship between the relative positional relationship and the optical axis and the outer periphery of the reference object is calculated. Based on the measurement, by calculating the position of the outer periphery of the test object relative to the optical axis of the test object,
The measuring method according to claim 1. A moving mechanism for moving an installation portion for positioning and installing at least one of the test object and the reference object relative to the measurement optical system;
In the first measuring step, when measuring the shape of the pre-Symbol reference plane, so as to match the optical axis of the measuring optical system and the optical axis of the reference object, through the installation part by the moving mechanism When moving the reference object and measuring the shape of the surface to be inspected, the moving mechanism causes the installation portion to be aligned with the optical axis of the object to be measured and the optical axis of the measurement optical system. The object to be moved through, and based on the amount of movement of the reference object by the moving mechanism and the amount of movement of the object by the moving mechanism, the relative positional relationship between the optical axes is calculated, Based on the relative positional relationship and the relationship between the optical axis and the outer peripheral portion of the reference object, the position of the outer peripheral portion of the test object is calculated with respect to the optical axis of the test object
The measuring method according to claim 1. A molding step of molding the optical element;
An evaluation step for evaluating the molded optical element by measuring the shape of the optical element that is the test object using the measurement method according to claim 1. Prepare
A method for manufacturing an optical element. A light source, a sheet catcher click Hartmann sensor, comprising: a measuring optical system, a calculation unit, and the shape measuring apparatus for measuring a test object,
The computing unit is
Wherein measuring the position of a plurality of light spots by the Shack-Hartmann sensor from the reflected light of the test object with respect to projected light, it acquires the positions of the plurality of light spots as the measured position data,
A reference position which is a position of a plurality of light spots formed by a reference object having a reference surface having a known shape and an outer peripheral portion around the reference surface and having a known positional relationship between the outer peripheral portion and the optical axis Based on the data and the test position data, by measuring the position of the outer periphery of the test object relative to the optical axis of the test object,
Based on the reference position data and the test position data, by measuring the shape of the test surface of the test object ,
A measuring device characterized by that. The calculation unit calculates a first difference, which is a difference in position between the optical axis of the reference object and the optical axis of the measurement optical system, based on the reference position data, and based on the test position data, A second difference that is a difference in position between the optical axis of the test object and the optical axis of the measurement optical system is calculated, and the relative position between the optical axes is calculated based on the first difference and the second difference. Calculate the relationship, based on the relationship between the relative positional relationship and the optical axis and the outer peripheral portion of the reference object, to measure by calculating the position of the outer peripheral portion of the test object relative to the optical axis of the test object,
The measuring apparatus according to claim 6. The calculation unit calculates the position of the optical axis of the reference object based on the reference position data, calculates the position of the optical axis of the test object based on the test position data, and calculates the light of the reference object. Based on the position of the axis and the position of the optical axis of the test object, a relative positional relationship between the optical axes is calculated, and based on the relationship between the relative position relationship and the optical axis and the outer periphery of the reference object, Measure by calculating the position of the outer periphery of the test object relative to the optical axis of the test object,
The measuring apparatus according to claim 6. A moving mechanism for moving an installation portion for positioning and installing at least one of the test object and the reference object relative to the measurement optical system;
When the shape of the reference surface is measured, the arithmetic unit is configured to cause the reference object and the optical axis of the measurement optical system to coincide with the reference object via the installation unit by the moving mechanism. When measuring the shape of the surface to be inspected, the moving mechanism causes the optical axis of the measurement optical system to coincide with the optical axis of the object to be inspected via the installation portion. The specimen is moved, and the relative positional relationship between the optical axes is calculated based on the amount of movement of the reference object by the moving mechanism and the amount of movement of the specimen by the moving mechanism, and the relative positional relationship Based on the relationship between the optical axis and the outer peripheral part of the reference object, the position of the outer peripheral part of the test object is calculated with respect to the optical axis of the test object.
The measuring apparatus according to claim 6.

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