JP2011215017A - Aspheric surface measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring apparatus constituted of a structure preventing a breakdown of an application end of an interference optical system due to a collision between a sample stage for holding a sample and an application end of the optical system when measuring an aspheric surface of a measured surface with high accuracy.SOLUTION: A sample holder mechanism A and an interference optical mechanism B are installed so as to allow relative movement severally, with the holder mechanism A for holding the sample 10 while the optical mechanism B composed of the interference optical system 2 for performing optical interference measurement by emitting measurement light. A breakdown of the optical system 2 is prevented by providing a low-strength part 64 on the sample stage 6 for holding the measured object 10 on its end in the holder mechanism A, the strength part 64 absorbing a shock in colliding with the application end 2a of the optical system 2.

Description

  The present invention irradiates measurement light onto a measurement surface (test surface) having an aspherical shape of a measurement object, and measures the measurement based on interference fringes obtained by interference between return light from the measurement surface and reference light. More particularly, the present invention relates to a structure of a sample stage that holds a measurement object.

  Conventionally, a method for identifying a local shape of a measurement surface based on interference fringes formed by interference between return light from the measurement surface and reference light by irradiating aspherical measurement surface with a spherical wave However, it is difficult to obtain interference fringes corresponding to the entire surface to be measured by such a method.

  Therefore, by sequentially moving the interferometer or the surface to be measured in the measurement optical axis direction, interference fringes corresponding to each partial region in the radial direction of the surface to be measured are sequentially generated. A technique is known in which the shape of each partial region in the radial direction of the measurement surface is obtained and the shape of the entire surface to be measured is specified by connecting them (see Patent Document 1 below).

  On the other hand, the interferometer or the surface to be measured is sequentially moved in a plane perpendicular to the measurement optical axis, and the interference fringes corresponding to each partial region of the surface to be measured are enlarged and imaged to the extent that the fringe analysis can be performed for each movement. A technique is also known in which each interference fringe is analyzed to determine the shape of each partial region of the surface to be measured, and the shape of the entire surface to be measured is specified by connecting them (see Patent Document 2 below).

JP-A-62-126305 US Pat. No. 6,956,657

  In recent years, the shape of an aspheric lens has become complicated. For example, in one lens surface (surface to be measured), a concave portion (concave surface portion) and a convex shape centered on the central axis of the lens surface An aspherical shape having a portion (convex surface portion) that is formed is used. It is considered difficult to measure the shape of the surface to be measured having such a concave portion and a convex portion by optical interference measurement, and until now, shape measurement has been performed by three-dimensional shape measurement using an optical stylus. It was.

  That is, in a general optical interference measurement method, an appropriate interference fringe is obtained only in the region where the measurement light irradiated on the measurement surface is retroreflected from the measurement surface (the return light travels backward in the original optical path). However, the measurement light applied to the surface to be measured is fixed to either a spherical wave that travels while diverging along the measurement optical axis or a spherical wave that travels while converging along the measurement optical axis In the methods described in Patent Documents 1 and 2, since the traveling direction of the return light from the measured surface is completely different between the concave surface portion and the convex surface portion, appropriate interference fringes are obtained in both the concave surface portion and the convex surface portion. It cannot be done.

  From the above points, the inventors of the present invention, for example, relatively measure the object to be measured and the interference optical system in three axes in the measurement of the aspherical shape having the concave surface and the convex surface as described above. In addition to being able to move in the direction, the optical interference measurement is performed while rotating the object to be measured around its central axis, and the angle formed between the central axis of the object to be measured and the measuring optical axis of the interference optical system is sequentially changed. Similarly, repeat the optical interference measurement while rotating the object to be measured about its central axis, analyze each interference fringe to find the shape of each partial area of the surface to be measured, and connect them together As a result of research, we have found that the method of identifying the shape of the entire surface to be measured is effective.

  At that time, the measurement object holding mechanism that holds the measurement object as described above and rotates around the central axis of the aspherical shape, and the interference optical system is held and the direction of the measurement optical axis is moved. When a measuring device is installed in which the mechanism is moved so that the relationship between the surface to be measured and the interference optical system has a predetermined relative orientation, the movement locus of the sample stage that holds the object to be measured, and the interference optical system Since the movement trajectory of the irradiation tip intersects, when setting the measurement object on the sample stage for measurement or when moving the sample stage to remove the measurement object after measurement, or When the relative posture of the two is adjusted to a predetermined state, the sample stage and the irradiation tip of the interference optical system may collide with each other and damage may occur.

  In particular, expensive optical elements such as an objective lens or a reference plate for obtaining reference light for interference are disposed at the irradiation tip of the interference optical system, and these optical elements are damaged due to the influence of a collision. Then, the parts are expensive, and high parts accuracy and mounting accuracy are required to ensure high measurement accuracy. Therefore, a lot of time and cost are required for the repair, and there is a problem in terms of measurement efficiency.

  The present invention has been made in view of such circumstances, and when measuring the aspherical shape of the surface to be measured with high accuracy, the sample stage that holds the object to be measured and the irradiation tip of the interference optical system. It is an object of the present invention to provide an aspherical shape measuring apparatus that prevents damage to the irradiation tip of an interference optical system due to collision.

  In order to achieve the above object, the aspherical shape measuring apparatus of the present invention is configured as follows.

That is, an aspherical shape measuring apparatus according to the present invention includes a measured object holding mechanism that holds a measured object having an aspherical measured surface, and irradiates the measured surface of the measured object with measurement light. An interference optical mechanism having an interference optical system for performing an optical interference measurement for obtaining an interference fringe due to interference between return light from the surface to be measured and reference light, and measuring the shape of the surface to be measured based on the interference fringe An aspherical shape measuring device,
The measured object holding mechanism and the interference optical mechanism are installed to be relatively movable,
The object holding mechanism includes a sample stage that holds the object to be measured at the tip, and the sample stage is provided with a low-strength portion that absorbs an impact when the sample stage collides with the irradiation tip of the interference optical system. It is characterized by that.

  In addition, the low-strength portion in the present invention can be configured with a notch structure.

  The sample stage includes a rotation stage unit that can rotate around the measurement surface axis of the object to be measured together with the object to be measured, and an adjustment unit that holds the rotation stage unit so that the rotation center position can be changed. It is preferable that the rotating stage unit is configured to be rotationally driven by a measured object rotating mechanism, and the low-strength unit is installed on the rotating stage unit.

Further, the measurement object holding mechanism in the present invention includes a measurement object rotation mechanism that rotates the measurement object about a measurement surface axis, and a measurement object rotation mechanism that is mounted and orthogonal to the measurement surface axis. A first slide mechanism that linearly moves in a direction or parallel direction,
The interference optical mechanism holds the interference optical system and rotates the interference optical system so that the measurement angle between the measurement optical axis and the axis of the surface to be measured can be changed, and the optical system rotation mechanism And a second slide mechanism that linearly moves in a direction orthogonal to the moving direction of the first slide mechanism.

  It is preferable that the first slide mechanism and the second slide mechanism are constituted by air slides.

  It is preferable that the object rotation mechanism and the optical system turning mechanism are constituted by an air spindle.

  The “measurement surface axis” refers to the central axis of the aspherical shape on the measurement surface of the object to be measured.

  The aspherical shape measuring apparatus according to the present invention has the following configuration and effects as follows.

  That is, in the aspherical shape measuring apparatus of the present invention, the measured object holding mechanism for holding the measured object having the aspherical measured surface, and the measurement surface of the measured object are irradiated with the measurement light and the measured object is irradiated. An interference optical mechanism having an interference optical system for performing optical interference measurement for obtaining an interference fringe due to interference between the return light from the measurement surface and the reference light is installed so as to be relatively movable. A sample stage for holding the object to be measured in the holding mechanism is provided with a low-strength part that absorbs an impact when it collides with the irradiation tip of the interference optical system. When the sample stage is moved in order to remove the object to be measured after measurement, or when the relative posture of the two is adjusted to a predetermined state, the sample step is performed. When the sample collides with the irradiation tip of the interference optical system, the low-strength part of the sample stage holding the object to be measured is deformed or broken to absorb the impact, and the irradiation tip of the interference optical system. Can be prevented from being damaged. Therefore, it takes a lot of time and money to repair the optical elements such as the objective lens and the reference plate arranged at the irradiation tip of the interference optical system without causing damage due to the impact of the collision. Can be prevented.

  In addition, if the low-strength part is configured with a notch structure, the low-strength part can be formed with a simple structure, and the sample stage deformed by a collision can be repaired in a short period of time by replacing parts, and measurement can be resumed early. Is possible.

  In addition, the sample stage according to the present invention includes a rotating stage unit that can rotate around the measurement surface axis together with the object to be measured, and an adjusting unit that holds the rotating stage unit so that the rotation center position can be changed. The stage unit is configured to be rotationally driven by a measured object rotation mechanism. When a low-strength unit is installed on the rotary stage unit, the measured object can be rotated and moved with predetermined characteristics, and the measurement function and It is possible to prevent the irradiation tip of the interference optical system from being damaged by the low-strength part while ensuring measurement accuracy.

  Further, a measured object rotating mechanism that rotates the measured object held about the measured surface axis, and a first slide mechanism that is mounted with the measured object rotating mechanism and moves linearly in a direction perpendicular to or parallel to the measured surface axis. A measurement object holding mechanism, and an interference optical system that performs optical interference measurement by irradiating the measurement surface with measurement light, and measuring the angle between the measurement optical axis and the measurement surface axis. An optical system turning mechanism that turns in a changeable manner and an interference optical mechanism that includes the optical system turning mechanism and that has a second slide mechanism that moves linearly in a direction orthogonal to the moving direction of the first slide mechanism are provided. The first slide mechanism and the second slide mechanism provided in the axial direction are separately operated to reduce the respective movement loads, thereby ensuring the movement accuracy and increasing the measurement accuracy. By arranging them separately, the structure can be made compact compared to the case where they are integrated, and it is not necessary to improve accuracy by increasing the rigidity of the peripheral members required in the integrated structure. Measurement accuracy can be ensured, and the rotational motion in two axes is separated into the measured object rotation mechanism and the optical swivel mechanism and operated separately to reduce the respective movement load and ensure the movement accuracy. As a result, the measurement accuracy can be increased, and the shape measurement of a minute aspheric lens or the like can be realized with high accuracy.

  Further, when the first slide mechanism and the second slide mechanism are constituted by air slides, wear due to use is not generated by using a gas as a lubricating film, and the movement accuracy of the measured object and the interference optical system, that is, the measurement accuracy is improved. It can be maintained well over a long period of time.

  Similarly, if the measured object rotation mechanism and the optical system turning mechanism are configured with an air spindle, wear due to use does not occur, and the measured object rotation accuracy and measurement angle change accuracy, that is, measurement accuracy is good over a long period of time. Can be maintained.

It is a principal part top view which shows the front-end | tip collision state of the to-be-measured object holding | maintenance mechanism and interference optical mechanism in the aspherical surface shape measuring apparatus which concerns on one Embodiment of this invention. It is a perspective view which shows schematic structure of the aspherical surface shape measuring apparatus which concerns on one Embodiment of this invention. It is the schematic front view which abbreviate | omitted the cover of FIG. FIG. 4 is a plan view in which the surface plate of FIG. 3 is omitted. It is a top view which shows the movement state of an example of FIG. FIG. 3 is a mechanism diagram showing configurations of an optical system and a control system in the embodiment of FIG. 2. It is an operation | movement flowchart which shows an example measurement operation | movement.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the mechanism diagram of FIG. 6, the size of each member, the distance between the members, and the like are appropriately changed with respect to FIGS. 1 to 5, and the detailed shape and structure are not shown.

  The aspherical shape measuring apparatus 1 of the present embodiment shown in FIGS. 2 to 6 measures and analyzes the aspherical shape of the rotationally symmetric measured surface 10a (see FIG. 6) of the measured object 10 (aspherical lens). The interference optical system 2 that irradiates the measurement surface 10a with measurement light and combines the return light from the measurement surface 10a with reference light to obtain interference light, and interference formed by the obtained interference light A first image pickup system 3 and a second image pickup system 4 for picking up the fringes, a measurement analysis system 5 (see FIG. 6) for analyzing the picked-up interference fringes to obtain the shape of the measurement target surface 10a, and the device under test 10 And a sample stage 6 whose holding posture can be manually adjusted.

  Then, a first air spindle 70 (measuring object rotating mechanism) that rotates the object to be measured 10 including the sample stage 6 and whose holding posture is adjusted around the surface axis S to be measured, and an X direction (surface to be measured) A measurement object holding mechanism A including a first air slide 7 (first slide mechanism) that moves in a straight line (slide) in a direction orthogonal to the axis S is configured. In addition, the interference optical system 2, the first imaging system 3, and the second imaging system 4, including a second air spindle 80 (optical system pivoting mechanism) that pivots around the Z direction that is the vertical direction, and the Y direction An interference optical mechanism B including a second air slide 8 (second slide mechanism) that moves in a straight line (slide) in the direction parallel to the measurement surface axis S is configured.

<Measurement holding mechanism A>
As shown in FIGS. 3, 4, and 6, the sample stage 6 includes a base portion 60 that serves as a movement base, an adjustment portion 61 that is attached to the base portion 60, and a rotating shaft that is attached to the adjustment portion 61. A rotary stage unit 62 installed so as to be capable of adjusting the position of E and the surface axis S to be measured (see FIG. 6), and rotatably held via a first air spindle 70 (measuring object rotation mechanism) described later; A measurement object holder 63 installed at the tip of the rotary stage unit 62 is provided, and the measurement object 10 is held by the measurement object holder 63.

  The rotary stage portion 62 in the sample stage 6 is formed in a rod shape by, for example, an aluminum-based material, and a part of the diameter is reduced in the middle of the rotary stage portion 62 as shown in FIG. A low-strength portion 64 having a notch structure is provided. This low-strength portion 64 breaks or deforms when it collides with the irradiation tip portion 2a of the interference optical system 2 and absorbs the impact, thereby preventing the irradiation tip portion 2a from being damaged.

  That is, FIG. 1 shows a state in which the measurement optical axis L of the interference optical system 2 is adjusted to a predetermined angle and moved in the Y direction in FIG. 5 according to the operation of the interference optical mechanism B having a moving mechanism described later. Thus, when the sample stage 6 moves upward, the tip of the rotating stage 62 of the sample stage 6 collides with the irradiation tip 2a of the interference optical system 2. When a force F indicated by an arrow is applied to the tip of the rotary stage unit 62 due to this collision, the low strength portion 64 provided so as to have a small diameter and a low bending strength due to the notch structure is directed downward in the figure. When the amount of deformation increases, it breaks and absorbs the impact, and the optically disposed optical element 2 is particularly arranged so that no deformation or damage occurs on the irradiation tip 2a side of the interference optical system 2. The element is not affected.

  The adjusting unit 61 is capable of manually adjusting the rotation center position of the rotary stage unit 62, that is, the workpiece holder 63, in the X direction and the Z direction within the plane, and the inclination of the rotation center is manually adjusted in the θX direction and the θZ direction. The initial adjustment with the measurement optical axis L of the interference optical system 2 to be described later is performed. By the adjustment, in the initial state, the measurement surface axis S of the DUT 10 and the rotation axis E of the adjustment unit 61 coincide with each other, and further, the measurement optical axis L of the interference optical system 2 coincides. Measurement starts after setting.

  The object to be measured 10 held on the sample stage 6 is rotated during measurement by the first air spindle 70 (measuring object rotation mechanism), and the first air slide 7 ( The position in the X direction is moved by the first slide mechanism. In other words, the first air spindle 70 is attached to the base portion 60 coaxially with the adjusting portion 61, and the rotational driving force is transmitted to the rotary stage portion 62 to rotate the rotary stage portion 62 together with the held object 10 to be measured. It is provided to operate.

  Further, the base portion 60 is mounted on a slide base 73 of the first air slide 7 so that the slide base 73 can slide on a guide 74 laid in the X direction on the surface plate 9 (anti-vibration base). It is placed. The first air slide 7 is a static pressure gas bearing, and pressurized air is introduced into the slide base 73, a gas lubricating film is generated in the gap with the guide 74, and the slide base 73 floats from the guide 74. The sliding base 73 is provided so as to be movable along the guide 74 by driving a motor (not shown). The position of the guide 74 is detected by an encoder (not shown), and the position in the X direction is controlled by the analysis control device 50.

  The first air spindle 70 is not shown in the figure, but a rotary shaft is rotatably held in the case through a gas lubrication film, and a servo motor is installed on the rotary shaft and is driven to rotate. The rotational position (rotation amount) is detected by the encoder, and the rotational position is controlled by the analysis control device 50.

<Interference optical mechanism B>
As shown in FIG. 6, the interference optical system 2 has a Fizeau type optical system arrangement, and includes a light source unit 20 that outputs a highly coherent light beam, and a beam diameter of output light from the light source unit 20. A beam diameter enlarging lens 21, a beam branching optical element 22 for reflecting interference light described later upward in the figure, a collimator lens 23 for collimating the light beam transmitted through the beam branching optical element 22, and the collimator A part of the plane wave from the lens 23 is retroreflected on the reference standard plane 24a to form reference light, and the rest is irradiated as measurement light traveling along the measurement optical axis L, and these optical elements. And a lens barrel 25 in which is stored. The plane reference plate 24 is held by a fringe scan adapter 28 provided with a piezo element 29, and is configured to finely move in the direction of the measurement optical axis L when performing fringe scan measurement or the like.

  At the irradiation tip 2a of the interference optical system 2, the flat reference plate 24 is installed as described above, and an optical element such as an objective lens is installed as necessary.

  Note that FIG. 6 shows the size changed for explanation. In particular, the diameter of the light beam applied to the measurement surface 10a as measurement light is very small with respect to the outer diameter of the measurement surface 10a. The measurement range is partial, and the measurement surface 10a is set in a measurement region that is concentrically divided into a plurality of annular zones (ring shapes having different diameters) as will be described later.

  The second imaging system 4 is mainly configured so that the measured surface 10a is in an initial posture (the measurement optical axis L and the rotation axis E coincide with each other and the measured surface axis S is parallel to the measurement optical axis L). A light beam for reflecting the interference light toward the first image pickup system 3 by being reflected upward by the light beam branching optical element 22 of the interference optical system 2. An imaging lens 40 for condensing the interference light transmitted through the branch optical element 34, an imaging camera 41 having a two-dimensional image sensor 42 composed of an area CCD, a CMOS, and the like, and a lens barrel containing these optical elements 45, and is configured to acquire image data of interference fringes formed on the two-dimensional image sensor 42 by the imaging lens 40.

  The first image pickup system 3 picks up an image when the surface to be measured 10a rotates, and forms an imaging lens 30 that collects the interference light reflected by the light beam splitting optical element 34 and traveling rightward in the drawing. And an imaging camera 31 having a one-dimensional image sensor 32 composed of a line CCD, a CMOS, and the like, and a lens barrel 35 housing these optical elements. It is configured to acquire image data of the interference fringes formed on the top.

  The lens barrel 25 of the interference optical system 2 is arranged in the horizontal direction (Y direction in the initial measurement state), and the lens barrel 45 of the second imaging system 4 is arranged in the vertical direction (Z direction) above the lens barrel 25. The lens barrel 35 of the first imaging system 3 is installed in parallel with the lens barrel 25, and the lens barrels 25, 35, and 45 are fixed to each other and moved integrally.

  The interference optical system 2 (the first imaging system 3 and the second imaging system 4) is turned when the measurement angle is changed by the second air spindle 80 (optical system turning mechanism), and when the measurement angle is changed. The position in the Y direction is moved by the second air slide 8 (second slide mechanism). That is, the lens barrel 25 of the interference optical system 2 is mounted on the upper end of the second air spindle 80 that is installed vertically so that the rotation axis is in the Z direction. The second air spindle 80 is held by the holding portion 81, and its rotational driving force is transmitted to the lens barrel 25, and the interference optical system 2 (the first imaging system 3 and the second imaging system 4) is moved along the Z axis. It is provided so as to be pivoted (θZ) as the center.

  Further, the holding portion 81 is mounted at an intermediate position of the base portion 82 of the second air slide 8 (see FIG. 4). The upper end of the base 82 in FIG. 4 is mounted on a slide base 83 of the second air slide 8, and the slide base 83 is installed in the Y direction (the first direction) installed on the surface plate 9 (vibration isolation base). It is slidably mounted on a guide 84 laid in a direction orthogonal to the moving direction of the air slide 7. The other lower end of the base 82 in FIG. 4 is held at a predetermined height by the air bush 86 so that the slide base 83 is horizontal. The air bushing 86 is configured such that the bottom surface of the air bushing 86 is floated with respect to the upper surface of the surface plate 9 through a gas lubrication film by the introduced compressed air, and slides on the surface plate 9 in a low friction state.

  Then, in the second air slide 8, the pressurized air is introduced into the sliding table 83 in the same manner as the first air slide 7, and a gas lubrication film is generated in the gap between the guide 84 and the sliding table 83 becomes the guide 84. The sliding table 83 is provided so as to be movable along the guide 84 by driving a motor (not shown). The position of the guide 84 is detected by an encoder (not shown), and the position in the Y direction is controlled by the analysis control device 50.

  Although the second air spindle 80 is not shown, a rotating shaft is rotatably held in the case through a gas lubrication film in the same manner as the first air spindle 70, and a servo motor is attached to the rotating shaft. It is a known structure that is installed and rotationally driven. The rotational position (rotation amount) is detected by an encoder, and the rotational position is controlled by the analysis control device 50. In the second air spindle 80, the portion of the interference optical system 2 that holds the lens barrel 25 can be moved up and down with respect to the base 82 and the slide base 83. It is moved up and down by the drive, its lift position is detected by the encoder, and the position in the Z direction is controlled by the analysis control device 50.

  Due to the operations of the measurement object holding mechanism A and the interference optical mechanism B, the measurement target surface 10a is positioned relative to the measurement optical axis L of the interference optical system 2 (inclination angle with respect to the measurement optical axis L and X, Y, and Z directions). (Position) can be changed freely.

  As shown in FIG. 2, the measurement object holding mechanism A and the interference optical mechanism B are installed on a surface plate 9, and the surface plate 9 is placed on a vibration isolation table 92 installed on a support leg 91. The upper space is covered with a cover 95 to prevent a decrease in measurement accuracy due to a sudden temperature change and humidity change in the measurement part. The cover 95 is provided with a front door 95a and an upper door 95b, which are opened when the object to be measured 10 is exchanged, etc., and can be operated by a measurer.

  The lifting actuator 87 in the interference optical mechanism B is installed extending downward from the surface plate 9, and in this case, a long hole (not shown) through which the lifting actuator 87 can move on the surface plate 9. Is formed so as to allow the interference optical system 2 to move in the Y direction.

<Measurement analysis system 5>
The measurement analysis system 5 receives the signal of the interference fringe image data acquired by the one-dimensional image sensor 32 and the two-dimensional image sensor 42, and based on the image data, the shape data of the measured surface 10a and the measured surface 10a. In order to calculate and analyze the surface eccentricity and to control a measurement operation as will be described later based on FIG. 7, the first air slide 7, the first air spindle 70 and the interference optical mechanism B of the measured object holding mechanism A are used. Drive signals a to f (see FIG. 6) are output to the second air slide 8, the second air spindle 80, and the lift actuator 87 to control the drive thereof, and the analysis control device 50 including a computer or the like, It comprises a display device 51 for displaying the analysis results and images by the analysis control device 50, and an input device 52 such as a keyboard or a mouse.

  The measured object 10 has a measured surface 10a that is rotationally symmetric about the measured surface axis S, and the measured surface 10a is a concave surface that is concave on the interference optical system 2 side. And a convex surface portion that is convex, and an off-axis stationary point portion that is located at the boundary portion between the concave surface portion and the convex surface portion, and based on the design data of the measured surface 10a, the measured device On the surface 10a, a plurality of measurement regions are set by dividing the surface 10a to be measured into a ring shape (concentric ring shape with different diameters) in the radial direction.

  Based on the interference fringe image captured by the two-dimensional image sensor 42 of the second imaging system 4 when the measured surface 10a assumes the initial posture, the measurement optical axis L and the measured surface axis S are adjusted to coincide with each other. The unit 61 is manually adjusted.

  In addition, the analysis control device 50 allows the measurement optical axis L at the intersection position so that the intersection position of the measurement optical axis L with the measurement target surface 10a sequentially moves on the plurality of set measurement areas. The relative orientation of the measurement optical axis L with respect to the surface to be measured 10a is set so that the moving portion does not interfere with each other so that the moving portion does not interfere with each other so that the tangent plane of the surface to be measured 10a intersects perpendicularly. (2) The drive of the air spindle 80 and the lifting actuator 87 is controlled. Further, by the operation of the first air spindle 70, the interference fringes for each measurement region imaged by the one-dimensional image sensor 32 of the first imaging system 3 while the surface to be measured 10a is rotated are imaged. A plurality of measurement regions divided by joining the shape information together with the shape information corresponding to each of the plurality of measurement regions based on the posture and rotation angle data of the measured surface 10a Are combined with each other to obtain shape information of the entire surface to be measured.

  Next, the measurement procedure of the aspheric surface shape measuring apparatus 1 in the present embodiment will be described based on FIG.

  First, after the power is turned on, an initial movement operation is performed in order to set the DUT 10. In step S1, the first air slide 7 on the left side is operated, and the slide stage 73 is moved in the vicinity of the measurer (operator) with the sample stage 6 on the near side so that the work for setting the object to be measured 10 can be easily performed. Subsequently, the second air slide 8 is operated to move the interference optical system 2 to the right side in a direction away from the sample stage 6 so as not to interfere with the work of setting the object to be measured 10. The work space is expanded (step S2).

  Thereafter, the front door 95 a and the upper door 95 b of the cover 95 are opened, and the measurer manually sets the device under test 10 to the device under test holder 63 at the tip of the rotary stage unit 62. Specifically, the measurer takes out the object to be measured 10 (a lens having an aspherical shape, etc.) from the storage position, carries it to the object holder 63 at the tip of the sample stage 6, and holds the object to be measured 10 in a predetermined posture. (Step S3). Then, the front door 95a and the upper door 95b of the cover 95 are closed, and after waiting for a predetermined time until the atmosphere (temperature and humidity) inside the cover 95 is stabilized, measurement is started.

  Next, measurement preparation is performed. In step S4, the first air slide 7 and the second air slide 8 are operated to bring the interference optical system 2 and the measured surface 10a of the measured object 10 into a directly-facing position, that is, The measurement surface axis S and the measurement optical axis L are moved to the directly facing position where they coincide. That is, the slide base 73 of the first air slide 7 is moved backward to move to the initial measurement position, while the second air slide 8 moves the slide base 83 forward to cover the irradiation tip of the interference optical system 2. While making it approach the measurement object 10, it moves to the measurement initial state where the to-be-measured surface axis | shaft S (rotation axis E) and the measurement optical axis L of the interference optical system 2 correspond on a straight line.

  In the initial setting (installation adjustment) of the aspherical surface shape measuring apparatus 1, the center position of the rotary stage unit 62 and the holding center position of the object holder 63, that is, the surface axis S of the object to be measured 10 coincide with each other. In addition, the center position (X position and Z position), angle (θX, θZ), and the like of the rotary stage 62 are set with respect to the rotation axis E of the first air spindle 70 by manual adjustment of the adjustment unit 61. At that time, the surface axis S to be measured using image data (interference fringes) of the two-dimensional image sensor 42 that captures the interference light at the center of the device under test 10 held in the device holder 63 to be measured by optical interference measurement described later. And the above-mentioned position adjustment can be performed.

  Further, in step S5, the second air spindle 80 is rotationally driven to adjust the measurement angle of the interference optical system 2 (the angle formed by the measured surface axis S and the measurement optical axis L) to a set angle. At this time, if the measurement angle is 0 degree and the position is directly facing (on a straight line), this operation is not necessary.

  Next, driving of the first air spindle 70 is started, rotation of the DUT 10 is started to enable measurement (step S6), and optical interference measurement is performed (step S7). In this measurement, the measurement light from the light source unit 20 is transmitted through the flat reference plate 24 to irradiate the measurement target surface 10a, and the reflected return light and the reference light from the reference reference plane 24a of the flat reference plate 24 are used. Image data of interference light formed by interference, that is, interference fringes (having reflection surface shape information) is captured using the one-dimensional image sensor 32 and the two-dimensional image sensor 42, and the image data is subjected to image processing. Then, measurement data is calculated by shape analysis, displayed on the display device 51, and stored. In the case of performing fringe scan measurement, the position of the flat reference plate 24 in the measurement optical axis L direction is appropriately changed using the fringe scan adapter 28, and measurement is performed for each change.

  When the optical interference measurement at the predetermined measurement angle is completed, the rotation of the object to be measured 10 by the first air spindle 70 is stopped in step S8, while the first air slide 7 is moved in step S9 for the next measurement. The slide table 73 is moved, and the DUT 10 is moved to a position in the X direction corresponding to the next measurement angle. At the same time, the second air spindle 80 is operated to rotate the measurement optical axis L of the interference optical system 2 by a predetermined angle (step S10), and the slide table 83 of the second air slide 8 is moved to cause interference optical. The Y direction position of the system 2 is changed.

  For example, when the measurement angle is changed from the directly-facing position in FIG. 4 to the orthogonal position in FIG. 5, the irradiation tip 2 a of the interference optical system 2 is in front of the X direction according to the turning operation of the second air spindle 80. As the Y direction moves to the right side (forward side) and to the right side (backward side), the first air slide 7 moves the object to be measured 10 forward in the X direction, while the second air slide 8 moves to the interference optical system. By moving 2 forward, the object to be measured 10 and the interference optical system 2 are adjusted so as to have a relative attitude of a predetermined distance and angle.

  After changing the measurement angle as described above, the measurement angle is changed while returning to step S6 and starting the rotation operation of the first air spindle 70 to rotate the DUT 10 about the measurement surface axis S. In step S7, the optical interference measurement is performed in the same manner.

  These measurement operations are sequentially repeated as many times as necessary for one object 10 to be measured, that is, the measurement for each predetermined angle set corresponding to the aspherical shape of the object 10 is completed. In this case, the process proceeds to step S12 to return the object to be measured 10 to the initial position. The first air slide 7 and the second air slide 8 are actuated to set the object 10 to be measured in step S3. The measured object 10 after measurement is removed from the measured object holder 63 in step S13, the next unmeasured object 10 is set, and the process returns to step S4. In the same manner as described above, the measurement angle corresponding to the newly set object 10 is set.

  When the above measurement operation is repeated for the number of objects to be measured 10 and all measurements are completed, the final object to be measured 10 is removed from the object holder 63 in step S13, and the power is turned off to stop. is there.

  As described above, the image data obtained by sequentially changing the measurement angle and performing the optical interference measurement is subjected to analysis processing on the annular zone shape information carried by the analysis control device 50, and the shape information of the entire surface to be measured 10a is obtained. Ask.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the above-mentioned embodiment, A various aspect can be changed.

  For example, in the above-described embodiment, the low-strength portion 64 is formed in a notch structure so that the bending area is reduced by reducing the cross-sectional area, and at the time of collision with the irradiation tip portion 2a of the interference optical system 2 However, the strength reduction structure can be modified such as using a low-strength material in addition to the cross-sectional area reduction structure. However, from the viewpoint of ensuring measurement accuracy, it is necessary to ensure the holding accuracy of the DUT 10, and it is inappropriate to form the material with flexibility or flexibility.

  In the above-described embodiment, the first air slide 7 is installed in the X direction and the second air slide 8 is installed in the Y direction. Conversely, the first air slide 7 is installed in the Y direction. The two air slides 8 may be installed in the X direction.

  In the above-described embodiment, the elevating actuator 87 is installed in the interference optical mechanism B. However, it may be configured to be provided in at least one of the measured object holding mechanism A.

  Moreover, in the above-mentioned embodiment, although the to-be-measured surface 10a is made into the shape which has a concave surface part and a convex surface part, a measuring object is not limited to the to-be-measured surface of such a shape. The aspherical shape measuring apparatus of the present invention can be used for measuring various measurement surfaces having various aspherical shapes that are rotationally symmetric.

DESCRIPTION OF SYMBOLS 1 Aspherical surface shape measuring apparatus 2 Interference optical system 2a Irradiation front-end | tip part 3 1st imaging system 4 2nd imaging system 5 Measurement analysis system 6 Sample stage 7 1st air slide (1st slide mechanism)
8 Second air slide (second slide mechanism)
DESCRIPTION OF SYMBOLS 9 Surface plate 10 Measured object 10a Measured surface 20 Light source part 21 Beam diameter expansion lens 22 Beam splitting optical element 23 Collimator lens 24 Plane reference plate 24a Reference reference plane 25 Lens barrel 28 Fringe scan adapter 29 Piezo element 30 Imaging lens 31 Imaging camera 32 One-dimensional image sensor 34 Beam splitting optical element 35 Lens barrel 40 Imaging lens 41 Imaging camera 42 Two-dimensional image sensor 45 Lens barrel 50 Analysis control device 51 Display device 52 Input device 60 Base unit 61 Adjustment unit 62 Rotation stage Part 63 Device holder 64 Low strength part 70 First air spindle (Measuring object rotating mechanism)
73 Slide base 74 Guide 80 Second air spindle (optical system turning mechanism)
81 Holding portion 82 Base portion 83 Slide table 84 Guide 86 Air bush 87 Lifting actuator (lifting mechanism)
91 Support leg 92 Anti-vibration table 95 Cover 95a Front door 95b Upper door A Measuring object holding mechanism B Interference optical mechanism E Rotating axis L Measuring optical axis S Measuring surface axis

Claims (6)

An object holding mechanism for holding an object to be measured having an aspherical surface to be measured, and interference between a return light from the surface to be measured and a reference light by irradiating the surface to be measured of the object to be measured An interference optical mechanism having an interference optical system for performing an optical interference measurement for obtaining an interference fringe, and an aspherical shape measuring apparatus for measuring the shape of the surface to be measured based on the interference fringe,
The measured object holding mechanism and the interference optical mechanism are installed to be relatively movable,
The object holding mechanism includes a sample stage that holds the object to be measured at the tip, and the sample stage is provided with a low-strength portion that absorbs an impact when the sample stage collides with the irradiation tip of the interference optical system. An aspherical shape measuring apparatus characterized by the above.   The aspherical shape measuring apparatus according to claim 1, wherein the low-strength portion has a notch structure.   The sample stage includes a rotation stage unit that can rotate around the measurement surface axis of the object to be measured together with the object to be measured, and an adjustment unit that holds the rotation stage unit so that the rotation center position can be changed. 3. The aspherical shape according to claim 1, wherein the rotary stage portion is configured to be rotationally driven by a measured object rotating mechanism, and the low-strength portion is installed on the rotary stage portion. measuring device. The measurement object holding mechanism includes a measurement object rotation mechanism that rotates the measurement object about a measurement surface axis, and a measurement object rotation mechanism that is mounted in a direction orthogonal or parallel to the measurement surface axis. A first slide mechanism for linear movement,
The interference optical mechanism holds the interference optical system and rotates the interference optical system so that the measurement angle between the measurement optical axis and the axis of the surface to be measured can be changed, and the optical system rotation mechanism The aspherical shape measuring apparatus according to any one of claims 1 to 3, further comprising: a second slide mechanism that is mounted and moves linearly in a direction orthogonal to the moving direction of the first slide mechanism.   The aspherical shape measuring apparatus according to claim 4, wherein the first slide mechanism and the second slide mechanism are constituted by air slides. The aspherical shape measuring apparatus according to claim 4, wherein the object rotation mechanism and the optical system turning mechanism are constituted by an air spindle.

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