JP2007218931A - Method and instrument for measuring shape of optical face, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily, surely, and precisely measure a shape of an optical face such as a lens face and a reflecting face. <P>SOLUTION: The optical face SF of an inspected object O is irradiated with a beam emitted from a light source 10, reflected light from the optical face SF is made to get incident into a photoreceiving face of a photoreceiving means 16 to be received by the photoreceiving means, and a reflection angle 2θ of the reflected light is measured to measure an inclination angle distribution of the optical face SF. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical surface shape measuring method and apparatus, and a recording medium.

  The fθ lens and camera lens mounted on the optical scanning device are prototyped many times during the final commercialization from the design and development stage. In these prototypes and products, it is necessary to measure the surface shape and surface accuracy with high accuracy in order to know whether the shape and accuracy of the lens surface actually formed satisfy the design specifications. Conventionally, several types of measuring machines are commercially available.

  Recently, with the development of aspherical processing technology, the required specifications for the measurement of optical surfaces have increased remarkably. In particular, lens surfaces such as fθ lenses have a high required accuracy on the order of nanometers (high resolution measurement), a wide measurement range (high dynamic range measurement), and a large tilt angle (high tilt angle measurement). Many of them have a free-form surface shape, and the conventional “three-dimensional shape measuring machine by xyz three-axis control” is becoming difficult to cope with, and the measurement method using an interferometer is extremely difficult to measure.

  For example, in the case where “waviness of amplitude: 5 nm and period: 10 mm” occurs as a shape error on an optical surface formed as a free-form surface, in order to measure this “waviness” with a three-dimensional coordinate measuring instrument, ( A three-dimensional ultraprecision measurement of 5 nm at the worst in the measurement accuracy of x, y, z) is necessary.

  Patent Document 1 discloses a surface shape measuring device having a configuration in which a 3-axis linear stage, a 2-axis rotary stage, and a laser length measuring machine for 6-axis position detection are attached. Due to the configuration, the apparatus becomes large and complicated, and the system tends to become unstable.

  The action of the optical surface used in the optical element is basically the action of refracting or reflecting light rays. From this point of view, in order to evaluate the optical performance of the optical surface in the optical element, the radius of curvature: R or the curvature: C (=) rather than the conventional method of measuring the coordinates (x, y, z) of the optical surface. It is more appropriate and straightforward to use (1 / R) and measure (x, y, R) or (x, y, C) on the optical surface. For example, (x, y, R) is the radius of curvature at the coordinates of the optical surface: x, y.

  If the optical surface is a lens surface, the direction in which the light beam is refracted by Snell's law is determined from the angle formed by the lens surface and the incident light beam. If the optical surface is a reflective surface, the reflection surface and the incident light beam are formed. This is because the direction of the reflected light ray is determined from the angle by the law of reflection, and the imaging position of the incident light ray is determined by the curvature or radius of curvature of the optical surface.

  As a conventional technique for measuring the curvature, there is one disclosed in Patent Document 2, but the reflected light from the optical surface is narrowed down on the light receiving element by the lens, and therefore, the angle of the angle formed by the reflected light with respect to the optical axis. The accuracy depends on the performance of the lens. For this reason, there exists a problem that the measurement precision of a curvature will be influenced by the performance of the said lens.

JP 11-2111427 A JP-A-6-294629

  It is an object of the present invention to easily and reliably measure the shape of an optical surface that is a lens surface or a reflecting surface.

  The shape measuring method according to claim 1, wherein “the beam emitted from the light source is irradiated onto the optical surface of the test object, the reflected light from the optical surface is incident on the light receiving surface of the light receiving means, and is received by the light receiving means, By measuring the reflection angle of the reflected light, the inclination angle distribution of the optical surface is measured ".

  The “test object” is an optical element having an optical surface to be subjected to shape measurement, and the “optical surface” is a lens surface or a reflective surface (mirror surface).

  According to a second aspect of the present invention, there is provided a shape measuring method comprising: irradiating an optical surface of a test object with a beam emitted from a light source, and causing reflected light from the optical surface to be incident on a light receiving surface of a light receiving means while preserving a light beam shape. By measuring the reflection angle of the reflected light received by the means and measuring the reflection angle of the reflected light, the inclination angle distribution of the optical surface is measured. "

  “Making the reflected light from the optical surface incident on the light receiving surface of the light receiving means while preserving the form of the light flux” changes the light flux form of the reflected light flux on the optical path from the optical surface to the light receiving surface of the light receiving means. This means that there is no optical system (convex lens / concave lens / convex mirror / concave mirror), and the reflected light is received by the light receiving means without changing the form of the light.

  If there is a lens or the like on the optical path from the optical surface to the light receiving means, the accuracy of the reflection angle of the reflected light depends on the performance of the lens or the like, as in the above-mentioned JP-A-6-294629. In the measuring method according to the second aspect, since the reflected light is received by the light receiving means while maintaining the luminous flux form, the reflection angle can be accurately measured, and the accuracy of the obtained inclination angle distribution is also good.

  In the shape measuring method according to claim 1 or 2, the "curvature radius distribution and / or curvature distribution of the optical surface" can be calculated by calculation based on the measured inclination angle distribution (claim 3). Further, in the shape measuring method according to claim 1, 2 or 3, the "average curvature radius distribution and / or average curvature distribution of the optical surface based on the measured inclination angle distribution" can be calculated by calculation (claims). 4).

  Further, in the shape measuring method according to claim 1, 2, 3, or 4, “adjusting the beam diameter and / or wavefront curvature radius at the optical surface irradiation position of the beam irradiated to the optical surface of the test object”. (Claim 5). By doing so, it is possible to effectively reduce the spread of the spot diameter of the reflected light formed on the light receiving surface of the light receiving means.

  In the shape measuring method according to any one of claims 1 to 5, "the wavefront of the beam irradiated on the optical surface of the test object can be an anamorphic wavefront" (claim 6).

  An “anamorphic wavefront” is a wavefront that is orthogonal to the beam direction and has different curvature radii in the directions orthogonal to each other.

  In this way, even when the optical surface is an anamorphic surface, it is possible to effectively reduce the spread of the spot diameter of the reflected light formed on the light receiving surface of the light receiving means in both directions orthogonal to each other. Become.

  In the shape measuring method according to any one of claims 1 to 6, the inclination angle of the optical surface of the test object may be measured by measuring the distribution of inclination angles in only one direction at a time. It is also possible to measure an "independent inclination angle distribution with respect to the axial direction" (claim 7).

  As described above, the optical surface of the test object is a lens surface or a reflection surface.For example, the design data of the optical surface is often known in advance, as in the case where the test object is a prototype, In such a case, it is possible to "calculate and calculate the shape error of the optical surface by comparing the design data of the optical surface of the test object with the actual measurement result" (claim 8).

  The “shape error” in this case is the difference between the designed optical surface shape and the actual optical surface shape.

  In the shape measuring method of the present invention, when the reflected light reflected by the optical surface of the test object is incident on the light receiving surface of the light receiving means in a wide spot shape, the reflected light is incident on the light receiving surface. Can be calculated by calculating the center of gravity of the reflected light received by the light receiving means and calculating the position of the center of gravity.

  The shape measuring method according to any one of claims 1 to 9, wherein "the optical surface of the test object, an optical system for irradiating the optical surface with a beam, and a light receiving means for receiving reflected light from the optical surface; Can be automatically controlled by the control means ”(claim 10).

  A shape measuring apparatus according to an eleventh aspect is an apparatus for carrying out the shape measuring method according to the first aspect, wherein the holding means, the light source, the optical unit, the light receiving means, the displacing means, and the calculating means are provided. Have.

“Holding means” is means for holding a test object.
The “light source” emits a beam that irradiates the optical surface of the test object.
The “optical unit” irradiates the optical surface of the test object with the beam emitted from the light source.

The “light receiving means” receives the reflected light reflected by the optical surface.
“Displacement means” is means for relatively displacing the incident position of the beam on the optical surface of the test object.

  The “calculation unit” calculates and calculates the inclination angle distribution of the optical surface based on the position of the reflected light received by the light receiving unit, the positional relationship between the optical surface and the beam.

  A shape measuring apparatus according to a twelfth aspect is an apparatus for carrying out the shape measuring method according to the second aspect, wherein the “light receiving means” in the above-mentioned claim 11 directly reflects the reflected light reflected by the optical surface. It is characterized by receiving light. That is, in the shape measuring apparatus according to the twelfth aspect, “an optical element having an imaging function” is not provided on the optical path from the optical surface to the light receiving surface of the light receiving means.

  In the shape measuring apparatus according to claim 11 or 12, the displacement means can "displace the position of the light receiving means while displacing the incident position of the beam on the optical surface" (claim 13). That is, in this case, the light receiving surface of the light receiving means is displaced to a position where the reflected light can be favorably received according to a change in the incident position on the optical surface.

  In the shape measuring apparatus according to claim 11, 12 or 13, the optical unit can have “a function of changing a beam diameter and / or a wavefront curvature radius at an optical surface position of a beam irradiated on an optical surface” ( Claim 14).

  In the shape measuring apparatus according to any one of claims 11 to 14, “the beam from the optical unit is irradiated onto the optical surface of the object via the beam splitter, and the reflected light from the optical surface is passed through the beam splitter. To the light receiving means ”(Claim 15). As in the case of the twelfth aspect, when the light receiving means receives the reflected light directly, a beam splitter that does not affect the luminous flux form of the reflected light is used.

  The shape measuring apparatus according to any one of claims 11 to 14, wherein the holding means has a function of tilting the optical surface of the test object by a desired angle with respect to the incident direction of the irradiated beam. (Claim 16).

According to the fifteenth and sixteenth aspects, the reflected light from the optical surface can be reliably incident on the light receiving surface of the light receiving means without returning to the optical unit side.
The light receiving means in the shape measuring apparatus according to any one of claims 11 to 16 may be configured to "measure the position coordinates of the reflected light from the optical surface of the test object at at least two places". (Claim 17).

  Further, the optical unit in the shape measuring apparatus according to any one of claims 11 to 17 can be configured such that “anamorphic optical elements for generating an anamorphic wavefront in an irradiation beam can be used” ( Claim 18).

  The calculation means in the shape measuring apparatus according to any one of claims 11 to 18 has a "function of calculating a curvature radius distribution and / or a curvature distribution of an optical surface by calculation based on a measured inclination angle distribution". (Claim 19).

  The calculation means in the shape measuring apparatus according to any one of claims 11 to 19 has a "function of calculating an average curvature radius distribution and / or an average curvature distribution of an optical surface by calculation based on a measured inclination angle distribution". (Claim 20).

  The calculation means in the shape measuring apparatus according to any one of claims 11 to 20, wherein the calculation means calculates and calculates an optical surface shape error by comparing the design data of the optical surface of the test object inputted in advance with the actual measurement result. It is possible to have a function to perform (claim 21).

  A recording medium according to claim 22 is a recording medium in which a program for controlling the shape measuring apparatus according to claim 11 or 12 is recorded, and “a start step, a measurement step, and a display step” are recorded as a program. Has been. The form of the medium is an optical information recording medium such as a compact disk, or a magnetic recording medium such as a floppy disk or a magnetic tape.

The “start step” is a step for realizing a measurement start state for the set specimen.
In the “measurement step”, a beam is emitted from the light source, a predetermined calculation is performed according to the light reception output of the light receiving means, an inclination angle is calculated and calculated, and the realization of the next measurement state for the test object is repeated. This is a step of obtaining a tilt angle distribution in a desired measurement region.

“Display step” is a step of displaying the result obtained in the measurement step.
The measurement step in the recording medium according to claim 22 can include a “step of calculating the curvature radius distribution and / or the curvature distribution of the optical surface based on the tilt angle distribution by calculation” (claim 23).

  The measurement step in the recording medium according to claim 22 or 23 can include a step of calculating an average curvature radius distribution and / or an average curvature distribution of an optical surface based on an inclination angle distribution by calculation (claim 24). .

  The measurement step in the shape measuring method according to any one of claims 22 to 24 is “calculating the shape error of the optical surface by comparing the design data of the optical surface of the test object inputted in advance with the actual measurement result”. (Calculating step) ”(Claim 25).

As described above, according to the present invention, a novel shape measuring method / shape measuring apparatus and recording medium can be realized. Unlike the conventional three-dimensional coordinate measurement, the measurement method / apparatus of the present invention measures the inclination angle distribution directly related to the optical performance of the optical surface and calculates and calculates the curvature distribution, etc. Is possible.
Further, in the measuring method of claim 2 and the measuring apparatus of claim 12, the reflected light from the optical surface is received by the light receiving surface of the light receiving means while preserving the form of the light beam. Unlike the case where there is a lens or the like on the optical path, measurement accuracy does not depend on the performance of the lens or the like, and accurate measurement is possible.
In addition, since the steps for carrying out the shape measuring method of the present invention are programmed and recorded on the recording medium of the present invention, if the hardware of the shape measuring apparatus is prepared, this hardware can be used as the recording medium. The shape measurement method of this method can be implemented only by controlling with a recorded program.

Embodiments of the invention will be described below.
In FIG. 1, reference numeral 0 is a test object, reference numeral 10 is a light source, reference numeral 12 is an optical unit, reference numeral 14 is a moving stage, reference numeral 16 is a light receiving device, reference numeral 18 is a moving stage, and reference numeral 20 is a control calculation means. Yes.

The test object 0 shown in the figure is a lens, and the shape of the optical surface SF is a measurement target.
For convenience of explanation, the x, y, and z directions are determined as shown in the figure. The y direction is a direction orthogonal to the drawing. The test object 0 is held on the moving stage 14. The moving stage 14 is a three-dimensional stage, and is capable of displacing the test object 0 in the x, y, and z directions under the control of the control calculation means 20.

  The light source 10 is a laser light source in this embodiment, but since this measuring apparatus does not use light interference, an LED or a white light source can be used in an appropriate form.

  A beam (laser light) emitted from the light source 10 is applied to the optical surface SF of the test object 0 via the optical unit 12. The optical unit 12 is used to adjust the beam form of the beam irradiated to the optical surface SF.

  The reflected light (regularly reflected light) reflected by the optical surface SF enters the light receiving surface of the light receiving device 16. In this embodiment, the light receiving device 16 is an area sensor using a CCD, but a position sensor or a divided photodiode can also be used.

  The light receiving device 16 is driven and controlled by the control arithmetic unit 20, and its output is input to the control arithmetic unit 20. The light receiving element 16 and the control calculation means 20 constitute a “light receiving means” in this embodiment.

  The moving stage 18 that holds the light receiving device 16 is a two-dimensional stage, and the light receiving surface of the light receiving device 16 is displaced within the “xy plane” under the control of the control calculation means 20.

  The moving stages 14 and 18 and the control calculation means 20 constitute “displacement means” in this embodiment.

  Based on the input information from the light receiving device 16, the control calculation means 20 calculates and calculates the tilt angle θ of the optical surface SF as described later. That is, in this embodiment, the control calculation means 20 constitutes “calculation means”. The control calculation means 20 is specifically a computer or the like.

That is, the shape measuring apparatus shown in FIG. 1 includes a holding unit 14 that holds the test object 0, a light source 10, an optical unit 12 that irradiates the optical surface SF of the test object with a beam emitted from the light source, and Light receiving means 16 and 20 for receiving the reflected light reflected by the optical surface, displacement means 14 and 20 for relatively displacing the incident position of the beam on the optical surface of the test object, and light received by the light receiving means. Based on the position of the reflected light, the optical surface, and the positional relationship between the beams, the calculation means 20 calculates and calculates the distribution of the inclination angle θ of the optical surface SF.
Further, the light receiving means 16 and 20 “directly receive the reflected light reflected by the optical surface” (claim 12).

  Hereinafter, measurement of the inclination angle distribution by the apparatus of FIG. 1 will be described. The optical surface SF generally has a three-dimensional shape, but a shape in the xz plane: z = z (x) will be considered below for the sake of simplicity.

  Since the reflected light from the optical surface SF is incident on the light receiving surface of the light receiving device 16 with “two-dimensional spread”, it is first necessary to specify the incident position of the reflected light on the light receiving surface. In this embodiment, since the light receiving device is a two-dimensional area sensor using a CCD, the incident position is specified as follows.

That is, the “coordinates of the reference position (for example, the center position of the light receiving surface)” of the light receiving surface of the light receiving device 16 that is two-dimensionally displaced by the two-dimensional stage 18 are parallel to X _S , Y _S (x, y direction). Yes).
Since the movement of the moving stage 18 is controlled by the control calculation means 20, the coordinates: X _S and Y _S exist as data in the control calculation means 20.

With the reference position of the light receiving surface as the origin, ξ coordinates are set in the x direction and η coordinates are set in the y direction. Since the light receiving surface is a “dense set of minute light receiving surfaces”, the coordinates of each minute light receiving surface are given by (ξ _i , η _j ).

  At this time, the incident position of the reflected light on the light receiving surface is assumed to be “the center of gravity of the light beam incident on the light receiving surface”. That is, the coordinates of the incident position are obtained by the well-known “centroid analysis”.

To explain an example, if the intensity of the reflected light incident on the coordinates: (ξ _i , η _j ) is P _ij , the ξ coordinates of the center of gravity: ξ _G
ξ _G = [Σ _i ξ _i {Σ _j P _ij η _j }] / Σ _ij P _ij
Given in. In this equation, “Σ _i ” means the sum for i, “Σ _j ” means the sum for j, and “Σ _ij ” means the sum for i and j.

Similarly, the η coordinate of the center of gravity: η _G
η _G = [Σ _i η _i {Σ _j P _ij ξ _j }] / Σ _ij P _ij
Given in.

When the center of gravity is determined in this way, the x coordinate of the “incident position on the light receiving surface” of the reflected light beam shown in FIG. 1: x (the reference is the principal ray position of the irradiation beam as shown in the figure) is x = X It is given by _S + _{ξ G.}

  That is, in this embodiment, the center of gravity of the reflected light received by the light receiving means is calculated, and the calculated position of the center of gravity is set as the incident position of the reflected light to the light receiving means.

  Further, the distance L in the figure represents the distance in the z direction between the light receiving surface position of the light receiving device 16 and the beam irradiation position on the optical surface SF. If this distance L is appropriately set at the time of measurement, the control calculation means 20 is stored as data.

Now, if the inclination angle (in the xz plane) at the beam irradiation position of the optical surface SF is “θ” as shown in the figure, the reflection angle of the reflected light is “2θ” according to the law of reflection. As is clear from the relationship between the incident position of the reflected light: x, the distance: L, and the angle: 2θ:
tan2θ = x / L (1)
Holds.

from now on,
2θ = arctan (x / L) (2)
Is obtained, the inclination angle: θ is calculated:
θ = 0.5 × arctan (x / L) (3)
Can be calculated. That is, the arithmetic means as the control operation unit 20 of obtains the "xi] _G" by the center of gravity analysis, calculates the x by the sum of the X _S, further, the inclination angle by the equation (3): calculates a theta. That is, the inclination angle: θ is the inclination angle at the beam irradiation position on the optical surface SF.

  The moving stage 14 is controlled by the control calculation means 20 to displace the test object 0 stepwise in the x direction by a predetermined minute distance: Δx, and the reflected light is incident on the light receiving surface of the light receiving device 16 at each step. By repeating the step of obtaining the position: x and obtaining the inclination angle: θ, the “inclination angle distribution in a cross section parallel to the xz plane” of the optical surface SF can be obtained. That is, in this case, what is obtained is a set of tilt angles at each beam irradiation position displaced by a minute distance: Δx in the cross section.

  When the height difference in the z direction of the optical surface is “somewhat large”, when the test object 0 is displaced in the x direction by the moving stage 14, simultaneously, the test object 0 is also displaced in the z direction, Distance: L should be kept unchanged. Since the data of the optical surface of the test object 0 is generally known as design data, the design data is stored in the control calculation means 20 in advance, so that the x-direction of the test object 0 is stored in the x direction. It is only necessary to calculate the minute change: Δz in the z direction with respect to the minute distance change: Δx, and to control the displacement distance of the test object 0 in the z direction by the moving stage 14.

  As another method, the displacement of the test object 0 by the moving stage 14 is only in the x direction, and instead of displacing the test object 0 in the z direction, the calculation is performed by correcting the distance: L with the above Δz. May be.

  After the “tilt angle distribution with respect to a certain cross section” of the optical surface is obtained as described above, the object 0 is moved to the y direction (direction orthogonal to the drawing) by the moving stage 14 as necessary. When the above process is repeated with the displacement, the tilt angle distribution (x, y, θ) can be known for the entire optical surface or a desired portion.

If the incident position of the reflected light on the light receiving device 16 changes greatly due to a change in the tilt angle: θ at the beam irradiation position and the incident position protrudes from the light receiving surface (based on the design data described above). It is preferable to control the moving stage 18 by the control calculation means 20 to displace the light receiving device 16 in the x and y directions so as to follow the change in the incident position of the reflected light.
In this case, the “displacement means” displaces the position of the light receiving means (by the moving stage 18) while displacing the incident position of the beam on the optical surface SF (by the moving stage 14) (claim 13). .

  That is, in the shape measuring apparatus shown in FIG. 1, the beam emitted from the light source 10 is irradiated onto the optical surface SF of the test object 0 and the reflected light from the optical surface SF is applied to the light receiving surface of the light receiving means 16. A shape measuring method (claim 1) for measuring the inclination angle distribution of the optical surface SF is performed by making the light incident, receiving the light by the light receiving means, and measuring the reflection angle: θ of the reflected light. At this time, the reflected light from the optical surface SF “enters the light receiving surface of the light receiving means 16 while preserving the form of the light flux” (claim 2).

Here, the shape measuring method will be specifically evaluated. L = 200 mm, position detection resolution: Δx = 1 μm, maximum inclination angle of optical surface SF of test object 0: θ _MAX is 30 degrees, minimum resolution: 0.5 seconds, dynamic range (= maximum inclination angle / minimum Resolution) = 2.2 × 10 ⁵ , and measurement with high accuracy and high dynamic range is possible.

  The case where the inclination angle distribution in the xy plane of the optical surface SF is measured has been described above. However, the coordinate in the y direction where the reflected light from the optical surface SF enters the light receiving surface of the light receiving device 16 is detected. By doing so, the inclination angle distribution in the yz plane can be measured in the same manner as described above. Since the moving stage 18 is a two-dimensional stage, it is easy to detect the incident position of the reflected light in the y direction (obtained by centroid analysis).

  Therefore, as described above, by independently measuring the x position and the y position of the incident position of the reflected light, an independent inclination angle distribution with respect to the biaxial direction of the optical surface SF of the test object 0 is measured ( Claim 7).

  As described above, if the inclination angle distribution of the optical surface can be measured, based on this result, the curvature distribution and the curvature radius distribution, and further the average curvature distribution and the average curvature radius distribution can be calculated. This will be described below.

  The coordinates specifying the surface position of the optical surface SF are X (parallel to the x direction in FIG. 1) and Y (parallel to the y direction in FIG. 1). These coordinates: X, Y are positions where the optical surface SF is irradiated by the beam from the optical unit 12 in FIG. 1 and are specified as data of the control calculation means 20 that controls the moving stage 14.

The inclination angles at the coordinates: X and Y are θ _X (X, Y) in the X direction and θ _Y (X, Y) in the Y direction.

The three-dimensional shape of the optical surface SF is “Z (X, Y)”, the curvature radius of the optical surface in the XZ plane at coordinates: X, Y is “R _X (X, Y)”, and the radius of curvature in the YZ plane is As “R _Y (X, Y)”, these are well known,
_{R X (X, Y) =} {1+ (∂Z / ∂X) 2} 3/2 / (∂ 2 Z / ∂X 2) (4)
_{R Y (X, Y) =} {1+ (∂Z / ∂Y) 2} 3/2 / (∂ 2 Z / ∂Y 2) (5)
Defined by

In the equation (4),
∂Z / ∂X = tan θ _X (X, Y) (6)
∂ ² Z / ∂ _X ² = ∂ tan θ _X (X, Y) / ∂ X (7)
And in equation (5):
∂Z / ∂Y = tan θ _Y (X, Y) (8)
∂ ² Z / ∂ _Y ² = ∂ tan θ _Y (X, Y) / ∂ Y (9)
Since it is, the inclination angle distribution was measured as described above: theta _X (X, Y) based on, (6) and (7) ∂ as "∂Z / ∂X by formula ^{2 Z} / ∂X ² ”And the right side of the equation (4) is calculated using the result, the radius of curvature of the optical surface to be measured: X, Y curvature radius; R _X (X, Y) can be calculated. Therefore, the curvature radius distribution: R _X (X, Y) can be obtained by performing such calculation for each position: X, Y.

Similarly, the inclination angle distribution: theta _Y (X, Y) based on, (8) and (9) calculating the "∂Z / ∂Y and ∂ ² Z / ∂Y ^2" by equation using the result If the right side of equation (5) is calculated, the radius of curvature at any surface position: X, Y of the optical surface: R _Y (X, Y) can be calculated. Is performed, it is possible to obtain a curvature radius distribution: R _Y (X, Y).

Since the curvature: C is the reciprocal of the radius of curvature: R, the curvature distribution in the XZ plane: C _X (X, Y) and the curvature distribution in the YZ plane: C _Y (X, Y) are respectively calculated:
_{C X (X, Y) =} 1 / R X (X, Y) = (∂ 2 Z / ∂X 2) / {1+ (∂Z / ∂X) 2} 3/2 (10)
C _Y (X, Y) = 1 / R _Y (X, Y) = (∂ ² Z / ∂ Y ² ) / {1+ (∂ Z / ∂ Y) ² } ^3/2 (11)
Can be calculated.

  That is, in the shape measuring apparatus whose embodiment has been described with reference to FIG. 1, the control calculation means 20 is configured to perform the calculations of the equations (4) to (9) or the equations (6) to (11). This is an embodiment of the shape measuring apparatus according to claim 19.

  And in such a shape measuring apparatus, the shape measuring method (Claim 3) which calculates the curvature radius distribution and / or curvature distribution of an optical surface based on the measured inclination-angle distribution is implemented.

As described above, measuring the inclination angle distributions θ _X (X, Y) and θ _Y (X, Y) independent of each other in the two X and Y axis directions means that the optical surface SF of the test object 0 is measured. This is particularly effective when the curvatures of are different in the biaxial directions.

  The tilt angle of the lens surface is optically “an important factor for determining the traveling direction of the emitted light”, but can be directly measured as described above according to the measuring method and apparatus of the present invention. Further, if the entire optical surface is decentered, the measurement result of the inclination angle distribution has a bias component with respect to the design value. As described above, the “decenter amount of the entire lens with respect to the reference” can also be measured.

  By the way, when the test object 0 is a scanning lens such as an fθ lens used in an optical scanning device, the most straight-line scale representing the optical performance is “the curvature or radius of curvature of the optical surface averaged within the incident beam diameter. “Average curvature or distribution of average curvature radius, ie, average curvature distribution or average curvature radius distribution”.

  Such an average curvature distribution or average curvature radius distribution can be obtained by performing an averaging operation on the above-described curvature distribution and curvature radius distribution if they are known. However, it is also possible to calculate directly from the inclination angle distribution without following such a procedure.

  When calculating the curvature distribution or the radius of curvature distribution from the inclination angle distribution and calculating the average curvature distribution from these curvature distributions, etc., the calculation scan is repeated for the actually measured inclination angle distribution, so errors in the calculation process are accumulated. However, if the average curvature distribution or the like can be calculated directly from the tilt angle distribution, such an accumulation of errors can be avoided.

For the sake of simplicity, the shape of the optical surface will be described as coordinates: X-only function: Z (X). The average curvature in the section of coordinates: X: [a, b]: <C (a: b)> is , By definition
<C (a: b)> = ∫ ab C (X) dX / (b-a) (12)
It is. “∫ _ab ” represents that the upper limit of integration is b and the lower limit is a.

Simplify equation (10) to a variable of X only,
C (X) = 1 / R (X) = (d ² Z / dX ² ) / {1+ (dZ / dX) ² } ^3/2 (13)
As a result of substituting into the above equation (12) and executing integration, the following equation (14) is obtained.

<C (a: b)>
= [{Z ′ (b) / √ (1 + Z ′ (b) ² )} − {Z ′ (a) / √ (1 + Z ′ (a) ² )}] / (b−a) (14 )
Here, Z ′ (a) = (dZ / dX) _{X = a} and Z ′ (b) = (dZ / dX) _{X = b} .

  Since dZ / dX = tan θ (X), by using the equation (14), the mean curvature in the section: [a, b]: <C (a: b)> is the inclination angle distribution: θ (X ) Can be easily calculated.

Here, if a = X ₀ −B / 2, b = X ₀ + B / 2, and the parameter: B is “beam diameter of the deflected beam incident on the optical surface of the scanning optical system”, the light enters the optical surface. The surface position of the beam to be calculated: “average curvature” at X = X ₀ is obtained. If X ₀ is changed over the incident area of the deflected beam, an “average curvature distribution” is obtained as a set of average curvatures for each surface position.

  The average curvature radius corresponding to <C (a: b)>: <R (a: b)> is defined as <R (a: b)> = 1 / <C (a: b)> by definition. Can be calculated. In the case of Z = Z (X, Y), the average curvature distribution and the average curvature radius distribution can be calculated in the same manner as described above.

  That is, in the shape measuring apparatus whose embodiment has been described with reference to FIG. 1, the control calculation means 20 calculates and calculates the average curvature distribution and the average curvature radius distribution of the shape measuring apparatus according to claim 20. This is one embodiment. In such an embodiment, the shape measuring method according to claim 4 is carried out, wherein “the average curvature radius distribution and / or the average curvature distribution of the optical surface is calculated based on the measured inclination angle distribution”. The

  When the test object 0 is a prototype lens, the shape data of the optical surface to be measured is known in advance as a design value. Therefore, in such a case, the optical surface shape data from the design data is input to the control calculation means 20 in advance, and the actual optical surface shape obtained from the inclination angle distribution measured as described above is used. By calculating the difference, it is possible to easily know the shape error of the optical surface in the prototype lens.

For simplicity, when the shape of the optical surface of the test object is Z (X), if the tilt angle distribution: θ (X) is known, this tilt angle distribution is expressed by the first derivative of the optical surface: dZ / dX. Since the relationship: dZ / dX = tan θ (X), tan θ (X) is obtained from the inclination angle distribution: θ (X), and the corresponding design dZ ₀ / dX (from the design data) Obtained): ΔZ ′ (X) = dZ / dX−dZ ₀ / dX was integrated with variable: X
ΔZ = ∫ΔZ '(X) dX (15)
This gives a “shape error”. In this way, it is possible to measure “waviness of the optical surface (shape error having spatial periodicity)” with an accuracy of the order of μm.

  Based on the known shape error, for example, it is possible to easily form the “optical surface closer to the design data” by correcting the surface of the lens surface molding die. . By measuring the shape as described above using the optical surface of the object to be measured as the measurement object and determining the shape error, the difference between the design mold surface and the actual mold surface can be calculated. You can also know directly.

  That is, in the embodiment of FIG. 1, the control calculation means 20 that can calculate the “shape error” is an embodiment of the shape measuring apparatus according to claim 19. The shape measuring method according to claim 8, wherein the measuring device calculates and calculates the shape error of the optical surface by comparing the design data of the optical surface of the test object with the actual measurement result.

  Further, in the measurement by the shape measuring apparatus whose embodiment is shown in FIG. 1, the optical surface SF of the test object 0, the optical systems 10 and 12 for irradiating the optical surface with the beam, and the reflection by the optical surface. The relative positional relationship with the light receiving means 16 for receiving light is automatically controlled by the control means 20 (claim 10).

  FIG. 2 is a diagram for explaining only a characteristic part of an embodiment of the shape measuring apparatus according to claim 14.

  In the embodiment described with reference to FIG. 1, in order to detect the position where the reflected light is incident on the light receiving surface of the light receiving device 16, the size of the spot formed by the reflected light on the light receiving surface of the light receiving device 16. However, it must be smaller than the size of the light receiving surface.

  If the optical surface is “a shape close to a flat surface” or “a loose concave surface or a loose convex surface”, even if the optical surface is irradiated with a substantially parallel light beam as an irradiation beam, the degree of divergence of the reflected light is small, and the light receiving device 16 However, when the optical surface is convex, the degree of divergence of the reflected light increases as the radius of curvature decreases, and the reflected light is received by the light receiving surface of the light receiving device 16. The case where it cannot be done will arise.

  In the shape measuring apparatus according to claim 14, in order to appropriately cope with such a situation, the optical unit is provided with “the beam diameter and / or the wavefront curvature radius at the optical surface position of the beam irradiated on the optical surface”. It has a function to change. In this way, by adjusting the beam diameter and the wavefront curvature radius according to the curvature of the optical surface, the degree of divergence of the reflected light can be controlled, and the reflected light can always be properly received by the light receiving surface of the light receiving device 16. It becomes possible.

  In the embodiment shown in FIG. 2, the optical unit 12A has a “function of changing the beam diameter and the wavefront curvature radius at the optical surface position of the beam irradiated on the optical surface”.

  In FIG. 2A, when the laser beam (parallel beam) emitted from the light source 10 enters the optical unit 12A, it is first condensed by the positive lens 121 and passes through the pinhole 122. Next, the light is collimated into a parallel beam by passing through the collimating lens 123. The collimating lens 123 has a zoom mechanism with a variable focal length, and can change the beam diameter of the exit beam.

  The parallel beam emitted from the collimating lens 123 passes through the opening of the aperture 124, is converted into a condensed beam by the lens 125, and is irradiated onto the optical surface SF of the test object 0.

  A desired wavefront curvature radius can be generated on the optical surface SF by adjusting the illustrated distance: 13 (the distance between the lens 125 and the optical surface SF) with respect to the focal length: f of the lens 125.

  In the drawing, a single lens 125 is shown. However, if a plurality of types of lenses (positive lens and negative lens) having different focal lengths can be switched together with the lens 125 to, for example, a revolver type, the test object An appropriate positive lens can be selected according to a wide range of 0 optical surface shape (curvature).

  In the example of FIG. 2, since the optical surface SF of the test object 0 is a convex surface, the wavefront of the beam that irradiates the optical surface is “a convex wavefront in the same direction as the optical surface SF”. When the optical surface is a concave surface, it is preferable to use a “wavefront convex toward the optical surface”. In this case, the lens 125 is arranged so as to satisfy l3> f, or the lens 125 is negative. A lens may be used.

  In the embodiment of FIG. 2, the spot diameter of the light spot formed by the reflected light on the light receiving surface of the light receiving device 16 can be obtained as follows.

(a) The wavefront curvature radius of the beam immediately before entering the lens 125: R and the focal length of the lens 125: f From the formula:
(1 / R ') = (1 / R)-(1 / f) (16)
To calculate the wavefront curvature radius R ′ of the beam “immediately after passing through the lens 125”.

(B) From this wavefront radius of curvature: R ′ and the beam radius of the Gaussian beam: w, the beam waist radius: w ₀ is given by the formula:
w ₀ = w / √ {1+ (πw ² / λR ′) ² } (17)
The beam waist position z ₀ is calculated by the following formula:
z ₀ = R ′ / {1+ (λR ′ / πw ² ) ² } (18)
Calculated by Note that λ is the wavelength of the beam.

Then, the beam radius: w (z) at the position away from the beam waist position: z ₀ by the distance: z is expressed by the following formula:
w (z) ² = w ₀ ² [1+ (λz / πw ₀ ² ) ² ] (19)
Is satisfied, and the wavefront radius of curvature R (z) at a position away from the beam waist position: z ₀ by a distance z is represented by the formula:
R (z) = z {1+ (πw ₀ ² / λz) ² } (20)
Satisfied. Accordingly, w (z) is obtained from (19), and the wavefront radius of curvature: R (z) can be obtained from equation (20).

In this R (z), the z coordinate of the position of the optical surface SF given as z is the wavefront curvature radius at the position of the optical surface SF of the beam incident on the optical surface SF, and this wavefront curvature radius is expressed as “ Rin "will be written (see FIG. 2B). Further, as shown in the figure, when the curvature radius (at the beam incident position) of the optical surface SF is “Rm” and the wavefront curvature radius immediately after reflection of the reflected light reflected by the optical surface SF is “Rout”, Between these radii of curvature: Rin, Rm, Rout:
(1 / Rin) + (1 / Rout) = 1 / Rm (21)
Therefore, according to this equation, the wavefront curvature radius Rout of the reflected light can be calculated. Once this wavefront radius of curvature: Rout is known, the size of the spot of the reflected light on the light receiving surface can be known if the distance: 14 between the optical surface SF and the light receiving surface of the light receiving device 16 is known.

  As an example, when the beam irradiation position portion of the optical surface SF is a “convex surface having a radius of curvature: Rm = 200 mm”, a parallel beam having a wavelength: λ = 633 nm is incident on the lens 125 at a beam radius: w = 0.5 mm. Assuming that the focal length of the lens 125 is f = 120 mm and the distance between the lens 125 and the optical surface SF is l3 = 50 mm, the wavefront curvature radius of the beam incident on the optical surface SF: Rin = 70 mm, the beam radius: w = When the distance to the light receiving surface of the light receiving device 16 is 14 mm (= L) = 200 mm, the spot diameter of the reflected light is 0.29 mm.

  The incident position of the light spot of the reflected light formed in this way is calculated and determined as a gravity center position by a control calculation means (computer). Since the CCD pitch of the light receiving device is several μm, it is possible to obtain a resolution of about 1/10, that is, submicron by calculating the position of the center of gravity.

  If the wavefront curvature radius: Rout is equal to the distance l4 between the optical surface SF and the light receiving surface, the spot diameter of the reflected light on the light receiving surface is the smallest and best. However, since the curvature radius of the optical surface: Rm and the distance: 14 may vary during the measurement, the light spot may be of a size that does not “extend” from the light receiving surface.

In order to obtain the incident position of the reflected light from the intensity distribution of the light spot on the light receiving surface by centroid analysis, the light spot radius on the light receiving surface is desirably 0.5 mm or less, for example. In this case, from equation (19), when the beam waist radius: w ₀ is 0.01 mm, the allowable range for the position of the light receiving surface (the allowable range for the distance: 14) is ± 25 mm, and the beam waist radius: w ₀ is 0.1 mm. when the allowable range ± 243mm, the beam waist radius: _{w 0} is allowable range when 0.2mm is ± 455 mm, and the long as to position the light receiving surface within the permissible range, the light spot radius: 0.5mm The following can be achieved:

In order to perform “positioning of the incident position of the reflected light” with higher accuracy, if the light spot radius on the light receiving surface is 0.25 mm or less, the allowable range is ± 12 mm when the beam waist radius: w ₀ is 0.01 mm. When the beam waist radius: w ₀ is 0.1 mm, the allowable range is ± 114 mm, and when the beam waist radius: w ₀ is 0.2 mm, the allowable range is ± 149 mm.

  If the distance between the lens 125 and the optical surface SF: l3 changes within a range of 45 to 60 mm, the beam waist position changes greatly within a range of −74 mm to 21 mm from the light receiving surface, but the range of change of the beam diameter is as follows. It is about 0.29 to 0.35 mm, and hardly affects the accuracy of determining the incident position. Therefore, if the range of fluctuation of the distance: l3 is within 15 mm, there is no substantial influence on the accuracy of the inclination angle distribution.

  According to the above explanation, for example, when “the beam radius immediately before entering the lens 125 is about 0.5 mm”, this beam radius corresponds to the beam diameter immediately after emission of a gas laser such as a He—Ne laser, and so on. In this case, the lenses 121 and 123 in the optical unit 12A in FIG. Therefore, since the optical unit can be realized only by the lens 125, the optical unit can be constituted by at least one lens (FIG. 1 shows this case).

  Accordingly, in the shape measuring apparatus described above with reference to FIG. 2, the optical unit 12A has the function of “changing the wavefront curvature radius at the position of the optical surface of the beam irradiated to the optical surface SF” (claim 14). The measurement method according to claim 5 is performed.

  As a next example, consider a case where the optical surface SF of the test object 0 is a convex surface with a radius of curvature: Rm = 25 mm. In this case, no matter how the distance 13 is changed, the spot diameter on the light receiving surface cannot be reduced to 1 mm or less. This is because a small wavefront curvature radius: Rin cannot be created.

  The following two methods can be considered as a method for dealing with this case. The first method is a method of changing the radius of the beam irradiated onto the optical surface SF to 3 mm in the optical surface shape. In this case, if the distance: l3 = 108 mm, the wavefront radius of curvature: Rout is 11.8 mm, and the spot diameter on the light receiving surface is 0.34 mm.

  The second method is a method using a lens 125 having a focal length of f = 25 mm. When the distance: l3 = 13.2 mm, the wavefront curvature radius: Rout is 12.0 mm, and the spot diameter on the light receiving surface is 0.34 mm.

  That is, in this case, the optical unit has a function of changing the beam diameter at the position of the optical surface of the beam irradiated on the optical surface (claim 14), and the method according to claim 5 Will be implemented.

  If the curvature of the optical surface that is the object of shape measurement is different between the X direction and the Y direction, the spot shape of the reflected light incident on the light receiving surface is, for example, an elliptical shape as shown in FIG. Become. In this case, the optical system is adjusted so that “the beam is thin” in one direction, the measurement is performed in one direction (for example, the X direction), and the measurement of the radius of curvature in the Y direction is performed by adjusting the optical system again. The measurement should be performed so that the spot diameter in the direction becomes smaller.

  Instead of doing this, an “anamorphic lens such as a cylinder lens” may be added to the optical unit 12A so that the spot diameter on the light receiving surface is “substantially circular”. Biaxial directions can be measured simultaneously (claims 18, 6 and 7).

  Specifically, the focal length: f and the distance: l3 are designed as described above for the lens 125 in one direction (X direction), and in the Y direction for the other direction (Y direction). A correction may be made by additionally arranging a cylinder lens having a curvature. When it is desired to change the diameter of the irradiation beam in the X and Y directions, a rectangular opening may be used as the opening of the aperture 124.

  In the case of the embodiment shown in FIG. 1 described above, when the tilt angle: θ of the optical surface SF is close to 0, the reflection angle of reflected light by the optical surface SF: 2θ is also small, and the position of the light receiving device and the light source / optical unit Since these positions interfere with each other, it is necessary to separate them from each other.

  For this purpose, for example, as in the embodiment shown in FIG. 3, the beam from the optical unit 12 is applied to the optical surface SF of the test object 0 via the beam splitter 30 such as a half mirror. The reflected light from the optical surface SF may be guided to the light receiving device 16 of the light receiving means via the beam splitter 30 (Claim 15), or as shown in the embodiment shown in FIG. As the holding means 14A, one having “a function of tilting the optical surface SF of the test object 0 by a desired angle with respect to the incident direction of the irradiated beam” may be used.

  As shown in FIG. 4, when the optical surface SF of the test object 0 is tilted relative to the irradiation beam, the value of the tilt angle itself changes. Ultimately, the “change amount of the tilt angle” is the curvature. There is no practical problem because it is a factor that affects the optical performance. The case described above is the case where the tilt angle on the optical surface is very small. Conversely, if the tilt angle of the optical surface exceeds 45 degrees, the reflected light does not enter the light receiving surface of the light receiving device. Even in such a case, it is effective to measure by tilting the optical surface of the test object.

  FIG. 5 is a view for explaining the characteristic part of the first embodiment of the shape measuring apparatus according to claim 17. The shape measuring apparatus according to claim 17 is characterized in that the light receiving means measures the position coordinates of the reflected light from the optical surface SF of the test object 0 in at least two places.

  In the embodiment of FIG. 5, (a) is an optical arrangement viewed in the xz plane, and (b) is an optical arrangement viewed in the yz plane. In order to measure the reflected light at two locations, a second light receiving device 17 is disposed in the light receiving means in addition to the light receiving device 16. Both the light receiving devices 16 and 17 can be displaced in the xy plane by a displacement means (not shown). In FIG. 5, reference numeral HM indicates a half mirror, and reference numeral BM indicates an irradiation beam incident on the half mirror.

  In the embodiment of FIG. 5, the second light receiving device 17 is a “transmissive photosensor”. For this reason, the reflected light from the optical surface SF passes through the light receiving device 17 and enters the light receiving device 17. The transmission position of the light receiving device 17 is determined by analyzing the center of gravity. Thus, by measuring the coordinates of two points on the optical path of the reflected light, the direction vector of the reflected light can be uniquely specified. When applied to the embodiment of FIG. 1, the lens 125, the optical surface SF, and Distance: The tilt angle can be measured even if L is unknown.

  In the embodiment of FIGS. 3 to 5 as well, the beam diameter at the optical surface irradiation position of the beam irradiated to the optical surface of the test object is the same as in the case of the embodiment described with reference to FIG. It goes without saying that the wavefront curvature radius can be adjusted and / or the wavefront of the beam applied to the optical surface of the test object can be an anamorphic wavefront.

  6 and 7 show examples of actual measurement values. FIG. 6 shows a “curvature radius distribution in a cross section” obtained by (virtually) cutting the optical surface along the XZ plane. FIG. 7 shows a two-dimensional curvature radius distribution as a three-dimensional overhead view for a certain optical surface.

  The radius-of-curvature distribution shown in FIG. 6 is a physical quantity directly linked to the optical performance, particularly the imaging position, and it can be seen at a glance how this radius of curvature is distributed. By the way, in this optical surface, it can be seen that the curvature is loose at the periphery. FIG. 7 shows an overview of the radius of curvature distribution of the entire optical surface. In this example, it can be seen at a glance that the radius of curvature changes greatly in the X direction with respect to the Y direction.

  In the embodiment described above, control and calculation of each part of the shape measuring apparatus are performed by the control calculation means 20, and the control calculation means 20 is specifically a computer or the like.

  In such a case, each control in the control arithmetic means 20 realized as a computer can be programmed and recorded on a recording medium such as a CD.

  As shown in FIG. 8, in this recording medium, a start step ST1 for realizing a measurement start state for the set specimen: a beam is emitted from the light source, and a predetermined calculation is performed according to the light reception output of the light receiving means. The step of calculating the inclination angle and the realization of the next measurement state for the test object are repeated to obtain the inclination angle distribution in the desired measurement region: ST2, and the result obtained in the measurement step The display step of displaying: ST3 is recorded as a program.

  Start step: In ST1, a message indicating that the test object should be set on the holding means is displayed. When the test object is set accordingly, design data on the optical surface of the test object should be input. When the display is performed and the design data is input, the step of positioning the test object at the measurement start position is recorded as a control program.

  Measurement step: ST2 includes processes as described in the above embodiments, that is, the displacement of the test object with respect to the irradiation beam, the displacement of the light receiving device, the blinking of the light source, the center of gravity analysis based on the output from the light receiving device, Calculation of tilt angle, adjustment of wavefront curvature radius and beam diameter of irradiation beam, calculation calculation of curvature radius distribution and curvature distribution, calculation of average curvature distribution and average curvature radius distribution, calculation of optical surface shape error, etc. The process is programmed and recorded.

  The display step ST3 includes a step of displaying various measurement results calculated in the measurement step ST2 in a predetermined output format (numerical data, image data as shown in FIGS. 6 and 7). , Programmed and recorded.

  Therefore, for example, if a computer is used as the control arithmetic device, the hardware as shown in FIG. 1 is configured, and the program recorded on the recording medium is read into the computer, the shape measuring device of the present invention can be configured. The shape measuring method of this invention can be implemented.

It is a figure for demonstrating one Embodiment of a shape measuring apparatus. It is a figure for demonstrating only another characteristic part of another form of implementation of a shape measuring apparatus. It is a figure for demonstrating only another feature part of another form of implementation of a shape measuring apparatus. It is a figure for demonstrating only another feature part of another form of implementation of a shape measuring apparatus. It is a figure for demonstrating only another feature part of another form of implementation of a shape measuring apparatus. It is a figure which shows one example of curvature radius distribution measured with the shape measuring apparatus of this invention. It is a figure which shows one example of the curvature radius distribution measured with the shape measuring apparatus of this invention as a three-dimensional bird's-eye view. It is a figure for demonstrating the step recorded on a recording medium.

Explanation of symbols

0 Test object SF Optical surface 10 Light source 12 Optical unit 16 Light receiving device

Claims (25)

  The beam emitted from the light source is irradiated onto the optical surface of the object to be measured, the reflected light from the optical surface is incident on the light receiving surface of the light receiving means, and is received by the light receiving means to measure the reflection angle of the reflected light. By measuring the inclination angle distribution of the optical surface, a method for measuring the shape of the optical surface is provided.   The beam emitted from the light source is irradiated onto the optical surface of the test object, and the reflected light from the optical surface is incident on the light receiving surface of the light receiving means while preserving the form of the light beam. A method for measuring the shape of an optical surface, comprising measuring an inclination angle distribution of the optical surface by measuring a reflection angle of light. In the shape measuring method according to claim 1 or 2,
A shape measuring method characterized by calculating a radius of curvature distribution and / or a curvature distribution of an optical surface based on a measured inclination angle distribution. The shape measuring method according to claim 1, 2 or 3,
A shape measuring method characterized by calculating an average curvature radius distribution and / or an average curvature distribution of an optical surface based on a measured inclination angle distribution. In the shape measuring method according to claim 1 or 2 or 3 or 4,
A shape measuring method comprising adjusting a beam diameter and / or a wavefront curvature radius at an optical surface irradiation position of a beam irradiated on an optical surface of a test object. In the shape measuring method according to any one of claims 1 to 5,
A shape measuring method, wherein a wavefront of a beam irradiated on an optical surface of a test object is an anamorphic wavefront. The shape measuring method according to any one of claims 1 to 6,
A shape measuring method comprising measuring an independent inclination angle distribution with respect to a biaxial direction of an optical surface of a test object. In the shape measuring method according to any one of claims 1 to 7,
A shape measuring method, comprising: calculating and calculating a shape error of the optical surface by comparing design data of the optical surface of the test object with an actual measurement result. In the shape measuring method according to any one of claims 1 to 8,
A shape measuring method characterized by calculating the center of gravity of reflected light received by the light receiving means, and setting the calculated position of the center of gravity as the incident position of the reflected light to the light receiving means. In the shape measuring method according to any one of claims 1 to 9,
The relative positional relationship between the optical surface of the test object, the optical system that irradiates the optical surface with the beam, and the light receiving means that receives the reflected light from the optical surface is automatically controlled by the control means. A characteristic shape measurement method. An apparatus for carrying out the shape measuring method according to claim 1,
Holding means for holding the test object;
A light source;
An optical unit for irradiating the optical surface of the test object with the beam emitted from the light source;
A light receiving means for receiving the reflected light reflected by the optical surface;
Displacement means for relatively displacing the incident position of the beam on the optical surface of the test object;
A shape having an arithmetic means for calculating and calculating a tilt angle distribution of the optical surface based on a position of reflected light received by the light receiving means, a positional relationship between the optical surface and the beam. measuring device. An apparatus for carrying out the shape measuring method according to claim 2,
Holding means for holding the test object;
A light source;
An optical unit for irradiating the optical surface of the test object with the beam emitted from the light source;
A light receiving means for directly receiving the reflected light reflected by the optical surface;
Displacement means for relatively displacing the incident position of the beam on the optical surface of the test object;
A shape having an arithmetic means for calculating and calculating a tilt angle distribution of the optical surface based on a position of reflected light received by the light receiving means, a positional relationship between the optical surface and the beam. measuring device. The shape measuring apparatus according to claim 11 or 12,
A shape measuring apparatus characterized in that the displacement means displaces the position of the light receiving means while displacing the incident position of the beam on the optical surface. The shape measuring apparatus according to claim 11, 12 or 13,
An optical unit has a function of changing a beam diameter and / or a wavefront curvature radius at an optical surface position of a beam irradiated on an optical surface. In the shape measuring apparatus according to any one of claims 11 to 14,
A shape measuring apparatus for irradiating an optical surface of a test object with a beam from an optical unit via a beam splitter, and guiding reflected light from the optical surface to a light receiving means via the beam splitter. In the shape measuring apparatus according to any one of claims 11 to 14,
The shape measuring apparatus, wherein the holding means has a function of tilting the optical surface of the test object by a desired angle with respect to the incident direction of the irradiated beam. In the shape measuring apparatus according to any one of claims 11 to 16,
A shape measuring apparatus, wherein the light receiving means measures the position coordinates of the reflected light from the optical surface of the test object at at least two locations. The shape measuring apparatus according to any one of claims 11 to 17,
An optical unit can use an anamorphic optical element for generating an anamorphic wavefront in an irradiation beam. In the shape measuring apparatus according to any one of claims 11 to 18,
A shape measuring apparatus, wherein the calculation means has a function of calculating a curvature radius distribution and / or a curvature distribution of an optical surface based on a measured inclination angle distribution. In the shape measuring apparatus according to any one of claims 11 to 19,
A shape measuring apparatus, wherein the calculation means has a function of calculating an average curvature radius distribution and / or an average curvature distribution of an optical surface based on a measured inclination angle distribution. In the shape measuring apparatus according to any one of claims 11 to 20,
A shape measuring apparatus, wherein the calculating means has a function of calculating and calculating the shape error of the optical surface by comparing the design data of the optical surface of the test object inputted in advance with the actual measurement result. A recording medium recording a program for controlling the shape measuring apparatus according to claim 11 or 12,
A start step for realizing a measurement start state for the set specimen;
A beam is emitted from the light source, a predetermined calculation is performed according to the light reception output of the light receiving means, and the step of calculating the tilt angle and the realization of the next measurement state for the test object are repeated, and in a desired measurement region A measurement step for obtaining a tilt angle distribution;
A recording medium in which a display step for displaying a result obtained in the measurement step is recorded as a program. The recording medium according to claim 22, wherein
A recording medium comprising a step of calculating a curvature radius distribution and / or a curvature distribution of an optical surface by calculation based on an inclination angle distribution. The recording medium according to claim 22 or 23,
A recording medium comprising a step of calculating an average curvature radius distribution and / or an average curvature distribution of an optical surface by calculation based on an inclination angle distribution. In the shape measuring method according to any one of claims 22 to 24,
A recording medium characterized in that the measuring step includes a step of calculating and calculating the shape error of the optical surface by comparing the design data of the optical surface of the test object inputted in advance with the actual measurement result.

Images