JP2009300236A - Displacement detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement detecting device reducing a measurement error by an influence of surface roughness of a surface to be measured, and detecting a displacement of the surface to be measured with an accuracy suitable for a measurement purpose. <P>SOLUTION: A displacement detecting device 10A is provided with: an irradiating optical system 103a for converging a light emitted from a light source 102 with a first objective lens 114 to form an image on a surface to be measured TG; and a non-contact sensor 100A having a light receiving optical system 103b for converging a light reflected in the surface to be measured TG and making it enter a light receiving device 120. The non-contact sensor 100A is provided with a diffraction grating 130A between the light source 102 and the first objective lens 114, for dispersing the light irradiated on the surface to be measured TG to form an image at plural points. By irradiating plural beams on the surface to be measured TG, displacements in the surface to be measured TG are averaged, and thereby the measurement is less influeced by the surface roughness. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention detects whether or not the measurement target surface is at the focal position of the objective lens by using the optical astigmatism method, and when the objective lens is displaced so that the focal position of the objective lens becomes the measurement target surface The present invention relates to a displacement detection apparatus that can measure a surface to be measured from the amount of displacement of the objective lens. Specifically, by disposing a spectroscopic element between the light source and the objective lens, the surface accuracy of the surface to be measured can be accurately measured.

  Conventionally, displacement detectors have been widely used as devices for measuring the displacement and shape of a surface to be measured. In the displacement detector, the light emitted from the light source is condensed on the surface to be measured by the objective lens, the reflected light reflected by the surface to be measured is condensed by the astigmatic optical element and incident on the light receiving element, and astigmatism A non-contact sensor that generates a focus error signal by a method. Then, servo is applied using the focus error signal generated by the non-contact sensor, the objective lens is displaced so that the focal position of the objective lens becomes the surface to be measured, and the objective lens is integrally attached to the objective lens via the connecting member. The displacement of the surface to be measured is detected by reading the scale of the linear scale.

  However, the above-described displacement detection device has a problem in that high linearity of the focus error signal itself is poor and thus high detection accuracy cannot be obtained. Thus, a displacement detection device has been proposed in which a calibrated output signal corresponding to a focus error signal of a non-contact sensor is output from a calibration table (see, for example, Patent Document 1). In this displacement detection apparatus, in order to increase the accuracy of displacement detection, the numerical aperture (NA: Numerical Aperture) of the objective lens is increased to reduce the diameter of the light beam focused on the surface to be measured. By setting the beam diameter of light imaged on the surface to be measured to about 2 μm, for example, the detection accuracy of the linear scale is about several nm to several hundred nm.

Japanese Patent Laid-Open No. 5-89480

  However, in the displacement detection device disclosed in Patent Document 1 described above, the light imaged on the surface to be measured is reduced by reducing the beam diameter of the light imaged on the surface to be measured to achieve high resolution. Is scattered by the surface roughness of the surface to be measured, resulting in a measurement error. Further, there is a case where fine dust attached to the surface of the measurement surface is detected, and there is a problem that displacement information such as the displacement and shape of the measurement surface that is originally required cannot be obtained accurately.

  The present invention has been made in order to solve such problems, and can reduce measurement errors due to the influence of surface roughness of a surface to be measured, and detect displacement of the surface to be measured with accuracy suitable for the measurement purpose. An object of the present invention is to provide a displacement detection device capable of performing the above.

  In order to solve the above-mentioned problems, the present invention condenses light emitted from a light source by an objective lens and irradiates the surface to be measured, and forms an image on the surface to be measured by the irradiation optical system. A non-contact sensor that has a light receiving optical system that collects light reflected from the measurement surface and enters the light receiving device, and detects displacement information of the surface to be measured by a change in the image of the light incident on the light receiving device; A control unit that displaces the objective lens based on the displacement information of the measurement surface detected by the contact sensor and aligns the focal position of the objective lens with the measurement surface, and is attached to the objective lens of the non-contact sensor via a connecting member. A linear scale, and a displacement amount measuring unit that measures the amount of displacement of the linear scale when the objective lens is displaced by the control unit based on the displacement information of the surface to be measured. Measured between the objective lens Spectroscopic element that splits light irradiated to the surface a displacement detecting device is disposed.

  In the displacement detection device of the present invention, the light emitted from the light source by the non-contact sensor is dispersed by the spectral element of the irradiation optical system, and the dispersed light is condensed by the objective lens to obtain a desired range of the surface to be measured. For example, images are formed at a plurality of points. The light imaged at a plurality of points on the surface to be measured is reflected by the surface to be measured, collected by the light receiving optical system, and incident on the light receiving element.

  In the non-contact sensor, the light image incident on the light receiving element changes according to the distance of the surface to be measured from the objective lens, and the displacement information on the surface to be measured depends on the light image incident on the light receiving element. Is detected.

  In the non-contact sensor, reflected light of the light imaged at a plurality of points on the surface to be measured is incident on the light receiving element, whereby averaged displacement information of the surface to be measured is obtained. Then, in the displacement detection device, when the objective lens is displaced so that the focal position of the objective lens becomes the measurement target surface according to the averaged displacement information of the measurement target surface detected by the non-contact sensor. By measuring the amount of displacement of the linear scale, the shape of the surface to be measured is detected.

  According to the displacement detection device of the present invention, the image of the light incident on the light receiving element is displaced in the range where the light is irradiated on the surface to be measured by forming light in a desired range on the surface to be measured. It becomes an averaged shape. Thereby, since the displacement information averaged on the surface to be measured can be detected by the non-contact sensor, the displacement of the surface to be measured can be detected with the optimum detection accuracy according to the measurement purpose.

Hereinafter, embodiments of a displacement detection device of the present invention will be described with reference to the drawings.
<Configuration and Operation Example of Displacement Detection Device of First Embodiment>
FIG. 1 is a block diagram showing an example of a displacement detection apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the displacement detection apparatus 10A includes a non-contact sensor 100A, a control unit 200, a servo control unit 210, an actuator 300, a displacement amount measurement unit 400, a signal processing unit 404, and a display unit 140. With. In FIG. 1, the configurations of the non-contact sensor 100A, the actuator 300, and the displacement measuring unit 400 are simplified for convenience.

  FIG. 2 is a perspective view illustrating an example of the configuration of the non-contact sensor according to the first embodiment. As shown in FIG. 2, the non-contact sensor 100A includes a light source 102, a collimating lens 104, a diffraction grating 130A, a polarizing beam splitter 108, a λ / 4 plate 110, a mirror 112, and a first objective lens 114. A second objective lens 116, an astigmatism generation lens 118, and a light receiving element 120.

  In the non-contact sensor 100A, the collimating lens 104, the diffraction grating 130A, the polarization beam splitter 108, the λ / 4 plate 110, the mirror 112, and the first objective lens 114 constitute an irradiation optical system 103a. Further, the non-contact sensor 100A includes a first objective lens 114, a mirror 112, a λ / 4 plate 110, a polarization beam splitter 108, a second objective lens 116, and an astigmatism generation lens 118. A system 103b is configured.

  The light source 102 includes, for example, a semiconductor laser diode, a super luminescence diode, a light emitting diode, or the like. The light source 102 emits light such as laser light toward the collimating lens 104. The collimating lens 104 converts the light emitted from the light source 102 into parallel light. The light converted into parallel light is incident on the diffraction grating 130A.

  The diffraction grating 130A is an example of a spectroscopic element and is disposed between the light source 102 and the first objective lens 114. In this example, a transmissive diffraction grating is used as the diffraction grating 130A, and the light converted into parallel light by the collimating lens 104 is transmitted to obtain 0th-order and ± mth-order (m = integer) diffracted light. It is done. Here, as the diffraction grating 130 </ b> A, a transmission type sheet-like diffraction grating may be attached to the first objective lens 114, or a reflection type diffraction grating may be disposed on the mirror 112.

  The polarization beam splitter 108 transmits the irradiation light La, which is diffracted light diffracted by the diffraction grating 130A, and makes it incident on the λ / 4 plate 110. The λ / 4 plate 110 converts the incident irradiation light La, which is linearly polarized light, into circular (elliptical) polarized light that rotates clockwise, for example. The irradiation light La that has passed through the λ / 4 plate 110 is reflected by the mirror 112 toward the measurement target surface TG of the measurement object, and is incident on the first objective lens 114.

  The first objective lens 114 is an optical element composed of a lens having a predetermined numerical aperture, and the first objective lens 114 is placed on the surface to be measured TG so that the focal position of the first objective lens 114 can be adjusted to the surface to be measured TG. It is configured to be movable in the approaching and separating directions. The irradiation light La incident on the first objective lens 114 is condensed on the measurement surface TG. Irradiation light La, which is 0th-order and ± mth-order diffracted light obtained by the diffraction grating 130A, is focused by the first objective lens 114, thereby forming images at a plurality of points on the measurement surface TG.

  FIG. 3 is a diagram showing an example of an irradiation pattern by an irradiation optical system having a diffraction grating. The irradiation light La, which is the 0th-order and ± mth-order diffracted light obtained by the diffraction grating 130A, is condensed on the surface to be measured TG by the first objective lens 114. Thus, a light beam spot B is formed.

  By adjusting the focal position of the first objective lens 114 to the surface to be measured TG, each of the irradiation light La, which is the 0th order and ± mth order diffracted light obtained by the diffraction grating 130A, is coupled to the surface to be measured TG. In accordance with the pattern of the diffraction grating 130A and the like, light is imaged in a desired pattern within a range of, for example, several mm on the measurement surface TG.

  The irradiation light La collected on the measurement surface TG is reflected by the measurement surface TG. The reflected light Lr reflected by the measurement surface TG passes through the first objective lens 114, is converted into parallel light, is reflected by the mirror 112, and enters the λ / 4 plate 110.

  The λ / 4 plate 110 further rotates incident reflected light, such as clockwise circular (elliptical) polarized light, further clockwise, and converts it into linearly polarized light whose linear polarization direction is rotated by 90 degrees with respect to the irradiation light La. To do. The reflected light Lr that has passed through the λ / 4 plate 110 enters the polarization beam splitter 108 again.

  The polarization beam splitter 108 reflects the reflected light Lr in the direction of the second objective lens 116 because the linearly polarized light direction of the incident reflected light Lr is rotated 90 degrees with respect to the irradiation light La. The reflected light Lr reflected by the polarization beam splitter 108 is incident on the second objective lens 116.

  The second objective lens 116 is an optical element composed of a lens having a predetermined numerical aperture, and condenses incident reflected light on the astigmatism generation lens 118 with a predetermined beam diameter. The astigmatism generation lens 118 has a shape obtained by dividing a cylinder into two in the axial direction, condenses light in a section having curvature, and transmits light as it is in a plane section. The reflected light Lr incident on the astigmatism generation lens 118 is condensed on the light receiving element 120.

The light receiving element 120 is supplied to the servo controller 210 generates a focus error signal (displacement information) S _FE based on the reflected light Lr is focused by an astigmatic generating lens 118. The light receiving element 120 is configured by a four-divided diode.

  4A to 4C are diagrams illustrating images of the reflected light Lr collected on the four-divided diodes. In the non-contact sensor 100A, as shown in FIG. 3, the reflected light of the light imaged at a plurality of points on the measurement surface TG is incident on the four-divided diodes constituting the light receiving element 120, so that the light receiving element 120 The incident light image has a shape in which the displacement in the range irradiated with light on the measurement surface TG is averaged.

When in the focal position of the measurement surface TG is the first objective lens 114 f1 (see FIG. 1), as shown in FIG. 4 (A), the condensed light becomes circular light spot L _R. Further, when the first objective lens 114 is moved away from the focus position f1 with respect to the measurement surface TG, as shown in FIG. 4B, an elliptical light spot L _RX spreading laterally is formed, and the focus position f1. When approaching further, as shown in FIG. 4C, an elliptical light spot _LRY spreads vertically.

Here, if the output signals output from each of the divided photodiodes are A, B, C, and D, a focus error signal S _FE representing a deviation from the focal position f1 is given by the following equation (1). .
S _FE = (A + C)-(B + D) (1)

FIG. 5 is a diagram illustrating characteristics of the focus error signal. The focus error signal S _FE given by equation (1) has characteristics as shown in the graph of FIG. In the characteristics shown in FIG. 5, when the origin O is the in-focus position and the distance between the first objective lens 114 and the measured surface TG is d, the focal length and the distance d are equal at the origin O.

Returning to FIG. 1, the servo control unit 210 is an example of a control unit, and adjusts the focal position of the first objective lens 114 to the measured surface TG based on the focus error signal _SFE output from the light receiving element 120. Take control. The servo control unit 210 includes a servo amplifier (not shown) and a comparison circuit. The servo amplifier amplifies the supplied focus error signal _SFE and supplies it to the comparison circuit. The comparison circuit compares a preset reference value with the focus error signal _SFE . The reference value is set within a range in which an error with respect to the focal position f1 is allowable, and is stored in, for example, the ROM of the comparison circuit. The servo control unit 210, as a result of comparing the reference value and the focus error signal S _FE, if the value of the focus error signal S _FE is above the permissible range of the reference value, such as a focus error signal S _FE is zero-value driving A signal (current signal) S _d is generated and supplied to the actuator 300.

The actuator 300 includes a movable coil 302, a permanent magnet 304, and a connecting member 500. A connecting member 500 is attached to the movable coil 302. A first objective lens 114 is attached to the connecting member 500. Moving coil 302 moves the connecting member 500 as a focus error signal S _FE in accordance with the drive signal S _d supplied from the servo control unit 210 becomes zero values in the arrow D1, D2 directions. In conjunction with this movement, the first objective lens 114 integrally attached to the connecting member 500 also moves in the directions of arrows D1 and D2, and the focal position f1 of the first objective lens 114 is moved to the measurement surface TG. At the same time, feedback control is performed so that the distance d between the surface to be measured TG is always equal to the focal length of the first objective lens 114.

  Since a voice coil motor is used as the actuator 300, the linearity with respect to the displacement of the surface to be measured TG is high. This is because the voice coil motor is a motor that is linearly displaced with respect to the current supplied to the movable coil 302. Therefore, the displacement amount can be easily detected by measuring the current supplied to the movable coil 302. The actuator 300 is not limited to a voice coil motor, and may be replaced with a DC servo motor, a stepping motor, a piezoelectric element, or the like.

  The displacement measuring unit 400 includes a linear scale 408 and a lattice interferometer 402. The linear scale 408 has a scale 406 formed at a predetermined pitch, and is attached to a predetermined position of the connecting member 500. The linear scale 408 is provided with an origin 410 at a substantially central position of the scale 406. Here, the scale 406 of the linear scale 408 is attached on the extension line Oa of the optical axis Lo of the first objective lens 114. In other words, the linear scale 408 is arranged on the same axis (inline) with respect to the optical axis Lo of the first objective lens 114. As the linear scale 408, for example, an optical scale (hologram scale) in which light interference fringes are recorded as a scale 406 can be used. Instead of an optical scale, a magnetic scale or a capacitive scale may be used.

Grating interferometer 402 is secured to a chassis or the like (not shown), to generate a memory read signal S _v reads the scale 406 of the linear scale 408, and supplies the generated scale read signal S _v to the signal processing unit 404. When the measured surface TG is displaced, the first objective lens 114 and the linear scale 408 are displaced by the same distance in the same direction so that the focal position f1 of the first objective lens 114 is held on the measured surface TG. The grating interferometer 402 reads this displacement amount from the scale 406 of the linear scale 408.

The signal processing unit 404 calculates the displacement amount of the measurement target TG based on the scale reading signal S _v output from the grating interferometer 402. Then, the signal processing unit 404 performs predetermined image signal processing based on the control signal S _S from the control unit 200, generates an image signal S _i based on the calculated displacement amount, and outputs it to the display unit 140. The image signal S _i generated by the signal processing unit 404 may be stored in a data logger (not shown).

The display unit 140 includes, for example, an LCD (Liquid Crystal Display), a PDP (Plasma Display Panel), or an EL (Electro Luminescence). The display unit 140 performs display based on the image signal S _i output from the signal processing unit 404 and displays the displacement of the measurement target surface TG on the screen of the display unit 140. Thereby, automatic measurement can be easily performed.

  The control unit 200 controls operations of the servo control unit 210 and the signal processing unit 404, and includes, for example, a CPU (Central Processing Unit), a ROM (Read-Only Memory), and a RAM (Random Access Memory). .

  As described above, according to the displacement detection apparatus 10A of the first embodiment, since the diffraction grating 130A is disposed between the light source 102 and the first objective lens 114, the diffraction grating 130A has zero-order and ± Irradiation light La, which is m-th order diffracted light, is obtained, and the surface to be measured TG can be irradiated.

  By adjusting the focal position of the first objective lens 114 that collects the irradiation light La to the surface to be measured TG, each of the irradiation light La that is the 0th order and ± mth order diffraction light obtained by the diffraction grating 130A. Are imaged on the measurement surface TG in an arbitrary pattern according to the grating pattern of the diffraction grating 130A, etc., at a plurality of points within a range of, for example, several mm on the measurement surface TG.

  Thereby, in the irradiation optical system 103a having the diffraction grating 130A, an effect equivalent to expanding the beam diameter of the light irradiating the measurement surface TG from the μm unit to the mm unit without reducing the resolution can be obtained.

  That is, in the non-contact sensor 100A, as shown in FIG. 3, the reflected light of the light imaged at a plurality of points on the surface to be measured TG is incident on the four-divided diodes constituting the light receiving element 120. The image of the light incident on 120 has a shape that averages the displacement in the range in which light is irradiated on the measurement target surface TG.

  In this way, the non-contact sensor 100A detects the averaged displacement information of the measurement surface TG, and sets the number of irradiation light La and the range irradiated with the irradiation light La according to the measurement purpose. The displacement of the measured surface TG can be detected with the optimum detection accuracy.

  Therefore, by irradiating the surface to be measured TG with a plurality of beams, it is possible to optically average the displacement of the range to be irradiated with the plurality of beams on the surface to be measured TG, and to be hardly affected by the surface roughness. Thus, the displacement of the measurement surface TG can be detected with high accuracy.

  As a result, displacement information that reacts sensitively to fine foreign matters attached to the surface of the measurement surface TG is not detected, and displacement information obtained by measuring the surface roughness of the measurement surface TG larger than the original is not detected. Without being detected, it is possible to detect displacement information obtained by measuring the original planar state of the surface to be measured TG.

  Further, the displacement amount obtained by the displacement detection device 10A described above is such that the linear scale 408 that moves integrally with the first objective lens 114 is coaxial with the optical axis Lo of the first objective lens 114. Since it is arranged on the so-called inline, Abbe error does not occur. For this reason, since the displacement amount of the linear scale 408 and the displacement amount of the first objective lens 114 correspond to 1: 1, the displacement amount can be detected with extremely high accuracy.

  Moreover, if it is within the detection range of the linear scale 408 (full scale of the scale 406), a wide detection range can be obtained without impairing the detection accuracy.

Further, since feedback control is used, no measurement error occurs even if the sensitivity of the focus error signal _SFE changes due to the reflectivity of the surface to be measured TG, and errors due to variations and drifts in the elements of the servo system and the actuator 300 occur. Therefore, the adjustment and calibration can be omitted, and stable detection can be performed over a long period of time.

  Further, by forming the origin 410 on the linear scale 408, there is an advantage that the amount of displacement of the measurement surface TG can be detected with the position of the origin 410 as the reference position.

<Configuration and Operation Example of Displacement Detection Device of Second Embodiment>
FIG. 6 is a block diagram illustrating an example of a displacement detection device according to the second embodiment of the present invention, and FIG. 7 is a perspective view illustrating an example of the configuration of the non-contact sensor according to the second embodiment. In addition, the same number is attached | subjected to the component which is common in the displacement detection apparatus 10A and non-contact sensor 100A which were demonstrated in 1st Embodiment mentioned above, and detailed description is abbreviate | omitted.

  The displacement detection device 10B according to the second embodiment includes a light scatterer 130B in the non-contact sensor 100B. The light scatterer 130B is an example of a spectroscopic element, and is disposed between the light source 102 and the first objective lens 114. The light scatterer 130B is a transmissive optical element having a random pattern shape and is intended to scatter light, and may be ground glass, a soft filter, a white resin material mixed with an emulsifying material, or the like.

  The displacement detection device 10 </ b> B according to the second embodiment converts light emitted from the light source 102 into parallel light by the collimator lens 104. The light converted into parallel light is incident on the light scatterer 130B and scattered.

  Irradiation light Lb, which is scattered light scattered by the light scatterer 130B, passes through the polarization beam splitter 108, is converted into circular (elliptical) polarized light by the λ / 4 plate 110, and is directed toward the measurement surface TG by the mirror 112. And is incident on the first objective lens 114.

  The irradiation light Lb incident on the first objective lens 114 is condensed on the measurement surface TG. In the irradiation optical system 103a having the light scatterer 130B, the light travels in various directions by being scattered by the light scatterer 130B. Therefore, the light is condensed by the first objective lens 114 and connected to the measurement surface TG. The imaged beam diameter is expanded compared to the case where the light scatterer 130B is not provided.

  The irradiation light Lb collected on the measurement surface TG is reflected by the measurement surface TG. The reflected light Lr reflected by the surface to be measured TG passes through the first objective lens 114, is converted into parallel light, is reflected by the mirror 112, is incident on the λ / 4 plate 110, and is applied to the irradiation light Lb. The linearly polarized light direction is converted into linearly polarized light rotated by 90 degrees. The reflected light Lr that has passed through the λ / 4 plate 110 enters the polarization beam splitter 108 again.

  The polarization beam splitter 108 reflects the reflected light Lr in the direction of the second objective lens 116 because the linearly polarized light direction of the incident reflected light Lr is rotated 90 degrees with respect to the irradiation light Lb. The reflected light Lr reflected by the polarization beam splitter 108 is incident on the second objective lens 116 and is collected on the astigmatism generation lens 118 with a predetermined beam diameter. In the astigmatism generation lens 118, the light is condensed in a section having curvature, and the light is transmitted as it is in a plane section, and the reflected light Lr is condensed on the light receiving element 120.

  In the non-contact sensor 100B, the reflected light of the irradiation light Lb irradiated on the measurement target surface TG by the irradiation optical system 103a having the light scatterer 130B is incident on the four-divided diode constituting the light receiving element 120 by the light receiving optical system 103b. As a result, the image of the light incident on the light receiving element 120 has a shape in which the displacement in the range of the beam diameter irradiated on the measurement target surface TG is averaged.

  The image of the light incident on the light receiving element 120 has the shape shown in FIG. 4A when the measurement target surface TG is at the focal position of the first objective lens 114, and the first objective lens 114 has the measurement target surface. When moving away from the focal position with respect to TG, the shape shown in FIG. 4B is obtained, and when approaching from the focal position, the shape shown in FIG. 4C is obtained.

In the light receiving element 120, a focus error signal (displacement information) _SFE is generated based on an image of incident light that changes in accordance with the distance between the first objective lens 114 and the measurement target surface TG. Based on the focus error signal _SFE output from the light receiving element 120, the servo control unit 210 performs feedback control for adjusting the focal position of the first objective lens 114 to the surface to be measured TG.

  A linear scale 408 is attached to the first objective lens 114 via a connecting member 500, and the first objective lens 114 when the first objective lens 114 follows the displacement of the surface TG to be measured. The amount of displacement is detected by reading the scale 406 of the linear scale 408 with the grating interferometer 402, and the amount of displacement of the measured surface TG is calculated by the signal processing unit 404.

  A high resolution can be achieved by reducing the beam diameter of the light focused on the measurement surface TG. On the other hand, if the diameter of the beam focused on the measurement surface TG is reduced, surface irregularities may be detected excessively due to factors such as a large surface roughness of the measurement surface TG.

  The irradiation optical system 103a having the light scatterer 130B is an optical system in which the beam diameter when there is no light scatterer is reduced to, for example, about 2 μm, and the beam diameter is expanded to, for example, about 4 μm by including the light scatterer 130B. be able to.

  As a result, even if the surface roughness is excessively detected when the beam diameter for irradiating the surface to be measured TG is reduced due to factors such as a large surface roughness of the surface to be measured TG, the influence of the surface roughness is affected. It is possible to detect the displacement of the surface to be measured TG with high accuracy.

  That is, by providing the irradiation optical system 103a with the light scatterer 130B, the beam diameter formed on the surface to be measured TG can be changed according to the surface degree of the surface to be measured TG, and the surface to be measured TG. Displacement information obtained by measuring the original planar state of the surface to be measured TG can be detected without detecting displacement information obtained by measuring the surface roughness of the surface to be larger than the original. Further, it is possible to easily cope with changing the measurement range, that is, changing the measurement resolution, and the displacement of the measurement surface TG can be detected with the optimum detection accuracy corresponding to the measurement purpose.

<Configuration and Operation Example of Displacement Detection Device of Third Embodiment>
FIG. 8 is a block diagram showing an example of a displacement detection device according to the third embodiment of the present invention, and FIG. 9 is a perspective view showing an example of the configuration of the non-contact sensor according to the third embodiment. In addition, the same number is attached | subjected to the component which is common in the displacement detection apparatus 10A and non-contact sensor 100A which were demonstrated in 1st Embodiment mentioned above, and detailed description is abbreviate | omitted.

  The displacement detection device 10C according to the third embodiment includes a microprism 130C in the non-contact sensor 100C. The microprism 130C is an example of a spectroscopic element, and is disposed between the light source 102 and the first objective lens 114.

  FIG. 10 is a perspective view showing an example of a microprism. The microprism 130C is a transmission optical element in which a plurality of prisms 131 are formed in a regular pattern shape, and incident light is split according to the number of surfaces of the prisms 131.

  The displacement detection device 10 </ b> C according to the third embodiment converts light emitted from the light source 102 into parallel light by the collimator lens 104. The light converted into the parallel light is incident on the microprism 130C and dispersed according to the number and orientation of the surfaces of the prism 131.

  The irradiation light Lc dispersed by the microprism 130C is transmitted through the polarization beam splitter 108, converted to circular (elliptical) polarization by the λ / 4 plate 110, reflected by the mirror 112 toward the measurement surface TG, 1 is incident on one objective lens 114.

  The irradiation light Lc incident on the first objective lens 114 is condensed on the measurement surface TG. In the irradiation optical system 103a having the microprism 130C, the irradiation light Lc dispersed by the microprism 130C is condensed by the first objective lens 114, thereby forming an image at a plurality of points on the measurement surface TG.

  The irradiation light Lc condensed on the measurement surface TG is reflected by the measurement surface TG. The reflected light Lr reflected by the surface to be measured TG passes through the first objective lens 114, is converted into parallel light, is reflected by the mirror 112, is incident on the λ / 4 plate 110, and is applied to the irradiation light Lc. The linearly polarized light direction is converted into linearly polarized light rotated by 90 degrees. The reflected light Lr that has passed through the λ / 4 plate 110 enters the polarization beam splitter 108 again.

  The polarization beam splitter 108 reflects the reflected light Lr in the direction of the second objective lens 116 because the linearly polarized light direction of the incident reflected light Lr is rotated 90 degrees with respect to the irradiation light Lc. The reflected light Lr reflected by the polarization beam splitter 108 is incident on the second objective lens 116 and is collected on the astigmatism generation lens 118 with a predetermined beam diameter. In the astigmatism generation lens 118, the light is condensed in a section having curvature, and the light is transmitted as it is in a plane section, and the reflected light Lr is condensed on the light receiving element 120.

  In the non-contact sensor 100C, the reflected light of the irradiation light Lc irradiated on the measurement target surface TG by the irradiation optical system 103a having the micro prism 130C is incident on the four-divided diode constituting the light receiving element 120 by the light receiving optical system 103b. Thus, the image of the light incident on the light receiving element 120 has a shape that averages the displacement in the range where the light is irradiated on the surface to be measured TG.

  The image of the light incident on the light receiving element 120 has the shape shown in FIG. 4A when the measurement target surface TG is at the focal position of the first objective lens 114, and the first objective lens 114 has the measurement target surface. When moving away from the focal position with respect to TG, the shape shown in FIG. 4B is obtained, and when approaching from the focal position, the shape shown in FIG. 4C is obtained.

In the light receiving element 120, a focus error signal (displacement information) _SFE is generated based on an image of incident light that changes in accordance with the distance between the first objective lens 114 and the measurement target surface TG. Based on the focus error signal _SFE output from the light receiving element 120, the servo control unit 210 performs feedback control for adjusting the focal position of the first objective lens 114 to the surface to be measured TG.

  A linear scale 408 is attached to the first objective lens 114 via a connecting member 500, and the first objective lens 114 when the first objective lens 114 follows the displacement of the surface TG to be measured. The amount of displacement is detected by reading the scale 406 of the linear scale 408 with the grating interferometer 402, and the amount of displacement of the measured surface TG is calculated by the signal processing unit 404.

  A high resolution can be achieved by reducing the beam diameter of the light focused on the measurement surface TG. On the other hand, if the diameter of the beam focused on the measurement surface TG is reduced, surface irregularities may be detected excessively due to factors such as a large surface roughness of the measurement surface TG.

  In the irradiation optical system 103a having the micro prism 130C, by irradiating the measurement target surface TG with a plurality of beams, the displacement of the range in which the plurality of beams are irradiated on the measurement target surface TG can be optically averaged. It is possible to detect the displacement of the surface to be measured TG with high accuracy without being affected by the surface roughness.

  The number and range of the irradiation light Lc imaged on the measurement surface TG can be set according to the number, direction, size, etc. of the surface of the prism 131 of the microprism 130C, and with the optimum detection accuracy according to the measurement purpose. The displacement of the measured surface TG can be detected.

<Configuration and Operation Example of Displacement Detection Device of Fourth Embodiment>
FIG. 11 is a block diagram illustrating an example of a displacement detection device according to a fourth embodiment of the present invention, and FIG. 12 is a perspective view illustrating an example of the configuration of a non-contact sensor according to the fourth embodiment. In addition, the same number is attached | subjected to the component which is common in the displacement detection apparatus 10A and non-contact sensor 100A which were demonstrated in 1st Embodiment mentioned above, and detailed description is abbreviate | omitted.

As shown in FIG. 12, the displacement detection device 10D of the fourth embodiment includes a spectral element switching member 130D in the non-contact sensor 100D. The spectroscopic element switching member 130 </ b _> D includes a plurality of types of spectroscopic elements 130 </ b _> D _{1 to} 130 </ b _> D _n that vary the light pattern formed on the surface TG to be measured, the beam diameter, and the like, and the light source 102 and the first objective lens 114. Arranged between.

The plurality of spectroscopic elements 130D _{1 to} 130D _n of the spectroscopic element switching member 130D include, for example, different diffraction gratings such as a grating pattern as the diffraction gratings of the first embodiment. In addition, as the transmission optical element having the random pattern shape of the second embodiment, transmission optical elements having different pattern shapes are provided. Alternatively, transmission optical elements having different pattern shapes are provided as the transmission optical elements having a regular pattern shape according to the third embodiment. Note that a transmission optical element having a diffraction grating and a random shape may be combined with a transmission optical element having a regular pattern shape.

Spectral element switching member 130D, a plurality of the spectral element 130D ₁ ~130D _n are coaxially arranged with respect to the axis O _R, by being driven to rotate around the axis O _R, the light source 102 by the irradiation optical system 103a Any of the spectroscopic elements 130D _{1 to} 130D _n is arranged on the optical axis to the surface to be measured TG.

  As shown in FIG. 11, the displacement detection device 10 </ b> D of the fourth embodiment includes the above-described non-contact sensor 100 </ b> D, the control unit 200, the servo control unit 210, the actuator 300, the displacement amount measurement unit 400, A signal processing unit 404, a display unit 140, and an operation unit 142 are provided.

The operation unit 142 includes, for example, a keyboard, a remote controller, and the like, and is used to select _one of the plurality of spectral elements 130D _{1 to} 130D _{n of} the spectral element switching member 130D. When a predetermined operation is performed by the user, the operation unit 142 generates an operation signal _So corresponding to the predetermined operation and outputs it to the control unit 200.

The control unit 200 generates a drive signal S _C for rotationally driving the drive unit 122 based on the operation signal S _o output from the operation unit 142 and outputs the drive signal S _C to the drive unit 122. When the spectroscopic element 130D _i is selected by the operation of the operation unit 142 by the user, the control unit 200 generates a drive signal S _C such that the spectroscopic element 130D _i is positioned on the optical axis Lo of the irradiation light L. .

Driver 122, on the basis of the drive signal S _C supplied from the control unit 200, a spectroscopic element switching member 130D which is connected through a shaft O _R to the driving unit 122 are rotationally driven to stop at a predetermined position. For example, when the drive signal S _C corresponding to the spectroscopic element 130D _i is supplied, the spectroscopic element switching member 130D is rotated and stopped so that the spectroscopic element 130D _i is positioned on the optical axis Lo.

According to the displacement detection device 10D of the fourth embodiment, by operating the operation unit 142, the spectroscopic elements 130D _{1 to} 130D _n adapted to these, for example, according to the characteristics, shape, and the like of the surface to be measured TG can be obtained. You can choose. Thereby, the displacement of the measurement surface TG can be measured with the optimum detection accuracy corresponding to the measurement surface TG, and the displacement information of the measurement surface TG suitable for the measurement purpose can be obtained. Therefore, it becomes possible to deal with various measurement objects.

<Experimental data comparison example>
Next, measurement results when the measurement surface TG is measured using a conventional displacement detection device and when the measurement surface TG is measured using the displacement detection devices 10A to 10D according to the embodiments of the present invention. explain.

  FIG. 13 is a graph showing an example of a measurement result obtained by a conventional displacement detection apparatus, and FIG. 14 is a graph showing an example of a measurement result obtained by a displacement detection apparatus to which the present invention is applied. Here, FIG. 14 is an example of measurement results using the light scatterer 130B described in FIGS. 6 and 7 as the spectroscopic element. FIGS. 13 and 14 show examples of measurement results displayed on the screens of the display units 140 of the displacement detection devices 10A to 10D, where the vertical axis is the surface roughness and the horizontal axis is the measurement position of the surface to be measured TG. is there. In FIGS. 13 and 14, it is assumed that the irradiation light L is scanned in a predetermined direction from the reference position (0 mm) of the measurement surface TG.

  In the conventional displacement detection device, the light emitted from the light source is irradiated onto the surface to be measured TG with a reduced beam diameter, so the surface roughness of the surface to be measured TG is measured to be larger than the original by increasing the resolution. As shown in the graph of FIG. 13, the uneven waveform appears greatly, and the original planar state of the measured surface TG cannot be measured.

  On the other hand, the displacement detection device to which the present invention is applied has an effect of averaging and measuring the displacement due to the surface roughness of the surface TG to be measured. As a result of measuring the same sample as before, the graph of FIG. It can be seen that the unevenness of the waveform is reduced as shown in FIG. 5 and the result of measuring the original planar state of the surface to be measured TG can be output.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention.

For example, in the embodiments, utilizes the astigmatism method to obtain a focus error signal S _FE, not limited to this, the critical angle method, it may be replaced by a knife edge method or the like. In any method, since the focus error signal _SFE is controlled to be zero, the displacement can be detected with high accuracy even if the reflectance of the surface to be measured TG is different.

  Further, the optical system composed of the light source 102, the polarization beam splitter 108, the mirror 112, and the light receiving element 120 may be attached to the connecting member 500 so as to move integrally with the first objective lens 114. It may be fixed to a chassis (not shown). By configuring so as to move integrally with the first objective lens 114, the displacement detection range is expanded to the full scale of the linear scale 408. When fixed to the chassis, that is, when configured in a distributed type, the actuator 300 can be made relatively small, and the weight of the displacement detection device including the first objective lens 114 and the like can be reduced. it can. This makes it possible to detect the displacement amount at a higher speed.

It is a block diagram which shows an example of the displacement detection apparatus of the 1st Embodiment of this invention. It is a perspective view which shows an example of a structure of the non-contact sensor of 1st Embodiment. It is a figure which shows an example of the irradiation pattern by the irradiation optical system which has a diffraction grating. It is a figure which shows the image of the reflected light condensed on a light receiving element. It is a figure which shows the characteristic of a focus error signal. It is a block diagram which shows an example of the displacement detection apparatus of the 2nd Embodiment of this invention. It is a perspective view which shows an example of a structure of the non-contact sensor of 2nd Embodiment. It is a block diagram which shows an example of the displacement detection apparatus of the 3rd Embodiment of this invention. It is a perspective view which shows an example of a structure of the non-contact sensor of 3rd Embodiment. It is a perspective view which shows an example of a microprism. It is a block diagram which shows an example of the displacement detection apparatus of the 4th Embodiment of this invention. It is a perspective view which shows an example of a structure of the non-contact sensor of 4th Embodiment. It is a graph which shows an example of the measurement result in the conventional displacement detection apparatus. It is a graph which shows an example of the measurement result in the displacement detection apparatus to which the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10A-10D ... Displacement detection apparatus, 100A-100D ... Non-contact sensor, 102 ... Light source, 108 ... Polarizing beam splitter, 114 ... 1st objective lens, 120 ... Light receiving element , 130A ... diffraction grating, 130B ... light scatterer, 130C ... microprism, 130D ... spectral element switching member, 200 ... control unit, 210 ... servo control unit, 400 ...・ Displacement measurement unit, 408 ... Linear scale, _SFE ... Focus error signal

Claims (5)

An irradiation optical system that condenses light emitted from a light source by an objective lens and irradiates the surface to be measured, and condenses light that is imaged on the surface to be measured by the irradiation optical system and reflected by the surface to be measured A non-contact sensor for detecting displacement information of the surface to be measured by a change in an image of light incident on the light receiving element;
A control unit that displaces the objective lens based on displacement information of the surface to be measured detected by the non-contact sensor, and aligns the focal position of the objective lens with the surface to be measured;
A linear scale attached to the objective lens of the non-contact sensor via a connecting member, and the linear scale when the objective lens is displaced by the control unit based on displacement information of the surface to be measured; A displacement amount measuring unit for measuring the displacement amount,
The non-contact sensor is a displacement detection device in which a spectroscopic element that disperses light irradiated on the surface to be measured is disposed between the light source and the objective lens.   The displacement detector according to claim 1, wherein the spectroscopic element is a diffraction grating that diffracts light emitted from the light source to obtain a plurality of diffracted lights.   The displacement detection apparatus according to claim 1, wherein the spectroscopic element is an optical element having a random pattern shape that scatters light emitted from the light source.   The displacement detection apparatus according to claim 1, wherein the spectroscopic element is an optical element having a regular pattern shape that refracts or reflects light emitted from the light source in different directions.   5. The displacement detection according to claim 1, further comprising: a spectral element switching member that switches a plurality of the spectral elements that change either or both of a light pattern imaged on the measurement target surface and a beam diameter. apparatus.

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