JP5670664B2 - Displacement detector - Google Patents

Description

  The present invention relates to a displacement detection device that uses light emitted from a light source to detect displacement of a surface to be measured by a non-contact sensor.

  Conventionally, displacement detectors have been widely used as devices for measuring the displacement and shape of a surface to be measured. In the conventional displacement detection device, the light emitted from the light source is condensed on the surface to be measured by the objective lens, and the reflected light reflected by the surface to be measured is condensed by the astigmatic optical element and incident on the light receiving element. A focus error signal is generated by the point aberration method. Then, the servo mechanism is driven using the focus error signal, and the objective lens is displaced so that the focal position of the objective lens becomes the surface to be measured. At this time, the displacement of the surface to be measured is detected by reading the scale of the linear scale that is integrally attached to the objective lens via the connecting member (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 5-89480

  However, the focus error signal indicating the amount of displacement of the objective lens may cause ringing-like waveform disturbance due to stray light or the like, and a plurality of zero-cross points indicating that the objective lens is at the reference position are generated. As a condition for driving the servo mechanism, the SUM (sum) signal of the amount of light received by each light receiving element when the objective lens is driven in the optical axis direction is larger than a certain value, and the focus error signal is at the zero cross point. In order to apply focus servo to the position of the objective lens that satisfies the two conditions, if the section in which the SUM signal is larger than a certain value (hereinafter referred to as the rising section of the SUM signal) is long, the focus error signal described above is included in the range. Many zero cross points occur, and in the worst case, there is a problem in that the servo mechanism is driven based on an erroneous zero cross point and the objective lens is displaced to an incorrect position.

  In addition, when the rising section of the SUM signal is long, there is a problem that the processing time until the servo mechanism is driven becomes long.

  On the other hand, if the rising edge of the SUM signal is long, a disturbance such as an impact is applied during the focus servo lock on the surface to be measured, and even if the focus servo is released and the objective lens moves slightly in the optical axis direction, the SUM signal is Since it is difficult to deviate from the signal rise interval, the number of processes required on the system side at the time of focus servo return can be reduced, and there is an advantage that the time until the focus servo return can be shortened. As described above, it is necessary to optimize the rising section of the SUM signal according to specifications such as a use environment and an operation state.

  In order to optimize the rising section of the SUM signal, it is conceivable to change the area of the light receiving element by replacing the light receiving element. However, there arises a problem that the light receiving element itself must be replaced.

  The present invention has been made in consideration of the above, and an object of the present invention is to provide a displacement detection device having an appropriate SUM signal rising section without changing the light receiving element.

  In order to achieve the above object, a displacement detection device of the present invention includes a light source, an objective lens, a separation optical system, a condensing unit, an astigmatism generating unit, a light receiving unit, a light amount adjusting unit, and positional information. And a generation unit. The objective lens condenses the light emitted from the light source toward the surface to be measured, and the separation optical system separates the optical path of the reflected light from the surface to be measured from the optical path of the light emitted from the light source. The condensing means condenses the reflected light separated from the optical path of the outgoing light by the separation optical system, and the astigmatism generating means generates astigmatism in the reflected light collected by the condensing means.

  The light receiving unit detects the light amount of the reflected light in which astigmatism is generated by the astigmatism generating unit, and the incident light beam diameter adjusting unit adjusts the light beam diameter of the reflected light from the measurement surface incident on the light receiving unit. The position information generation unit generates position information of the surface to be measured using a focus error signal obtained from the amount of light detected by the light receiving unit.

  In the displacement detection device having the above-described configuration, the incident beam diameter adjusting means can adjust the beam diameter of the reflected light from the surface to be measured incident on the light receiving unit, and set the rising section of the SUM signal to an arbitrary length. . Therefore, even when the length of the SUM signal rising section of the displacement detection device is changed, it is not necessary to replace the light receiving element itself. Also, by setting the rising edge of the SUM signal to be short, the possibility that the focus servo is applied to the erroneous zero cross point of the focus error signal is reduced. As a result, the objective lens can be displaced to an accurate position by the servo mechanism, and high-precision measurement can be performed. The incident light beam diameter adjusting means is preferably installed near the light receiving section, and can accurately adjust the light beam diameter of the reflected light from the surface to be measured incident on the light receiving element. It can be set more accurately.

  According to the displacement detection device of the present invention, it is possible to accurately measure the object lens by accurately displacing the objective lens.

It is a block diagram which shows embodiment of the displacement detection apparatus of this invention. It is explanatory drawing which shows the example of the irradiation image of the light-receiving part which concerns on embodiment of the displacement detection apparatus of this invention. It is a figure which shows the characteristic of the focus error signal and SUM signal obtained from the light quantity detected by the light-receiving part which concerns on embodiment of the displacement detection apparatus of this invention. It is a top view which shows the relative positional relationship of the aperture and light receiving element which concern on embodiment of the displacement detection apparatus of this invention.

  Hereinafter, the form for implementing the displacement detection apparatus of this invention is demonstrated with reference to FIGS. In each figure, the same code | symbol is attached | subjected to the common member.

First, an embodiment of a displacement detection device will be described with reference to FIG.
FIG. 1 is a block diagram showing an embodiment of a displacement detection device.

  As shown in FIG. 1, the displacement detection apparatus 1 includes a light source 2, an objective lens 3, a separation optical system 4, a mirror 5, two collimator lenses 6 and 7, an astigmatism generation unit 8, and a light reception. Unit 9, position information generation unit 10, housing 11, and light amount adjustment means 12. The light source 2, the objective lens 3, the separation optical system 4, the mirror 5, the two collimator lenses 6 and 7, the astigmatism generation unit 8, the light receiving unit 9, the position information generation unit 10, and the light amount adjustment unit 12 are each in a housing 11. It is arranged.

  The light source 2 is composed of, for example, a semiconductor laser diode or a super luminescence diode. The light source 2 is detachably attached to the housing 11. By detachably attaching the light source 2 to the housing 11, the deteriorated light source 2 can be replaced with a new light source without removing the housing 11 from the installation location. Thereby, there is no fear that the installation position of the housing 11 is shifted every time the light source 2 is replaced, which is advantageous when the displacement detection device 1 is used for a measurement or manufacturing device that requires reliability.

  The objective lens 3 condenses the emitted light from the light source 2 toward the surface to be measured 101. The objective lens 3 is fixed to a lens holding portion (not shown), and the lens holding portion can be moved in the optical axis direction of the objective lens 3 by an actuator (not shown). As an actuator for moving the lens holding portion, for example, a moving coil and a permanent magnet can be used.

  A linear scale (not shown) is fixed to the lens holding portion. The scale of this linear scale is arranged coaxially with the optical axis of the objective lens 3. As this linear scale, for example, an optical scale (hologram scale) recorded with light interference fringes as a scale, a magnetic scale, or the like can be used. In the linear scale, an origin (reference point) is preferably formed at a substantially central position of the scale.

  The separation optical system 4 includes a polarizing beam splitter 15 and a phase plate 16, and separates the optical path of reflected light from the surface to be measured 101 from the optical path of outgoing light from the light source 2. The polarization beam splitter 15 reflects the light emitted from the light source 2 and transmits the reflected light reflected by the surface to be measured 101. The phase plate 16 is disposed between the polarizing beam splitter 15 and the mirror 5 and changes the polarization state of the outgoing light reflected by the polarizing beam splitter 15 and the reflected light reflected by the surface to be measured 101.

  The mirror 5 changes the optical axis direction of the outgoing light reflected by the polarization beam splitter 15 and the reflected light reflected by the surface to be measured 101. Specifically, the optical axis of the outgoing light reflected by the polarization beam splitter 15 is directed to the objective lens 3, and the optical axis of the reflected light reflected by the surface to be measured 101 and passed through the objective lens 3 is changed to the phase plate 16 (polarized light). Directed to the beam splitter 15).

  A metal film is applied to the surface of the mirror 5. As a result, changes in polarization and wavelength characteristics due to changes in humidity caused by a general dielectric multilayer film can be suppressed, and stable position detection becomes possible.

  The collimator lens 6 is disposed between the light source 2 and the polarization beam splitter 15, and makes the emitted light from the light source 2 parallel light. The collimator lens 7 is disposed between the polarization beam splitter 15 and the astigmatism generation means 8. The collimator lens 7 is a specific example of a condensing unit, and condenses the reflected light that has passed through the polarization beam splitter 15 and guides it to the light receiving unit 9.

  It should be noted that the objective lens 3 and the collimator lenses 6 and 7 may be provided with an achromatic measure (chromatic aberration correction) that makes it difficult to receive the focal length variation due to the wavelength variation of the light source 2. By doing so, it is not necessary to monitor the wavelength and temperature of the light source 2, and it is not necessary to correct the measured value obtained by measuring the displacement amount of the surface to be measured 101.

  Further, in the present embodiment, the collimator lens 6 is disposed in the optical path of the emitted light emitted from the light source 2, and the collimator lens 7 is disposed in the optical path of the reflected light reflected by the surface to be measured 101. This makes it possible to arbitrarily set the optical path length of the emitted light and the optical path length of the reflected light. As a result, the degree of freedom in design can be improved, and optimal component placement can be realized. Furthermore, the collimator lens 6 can optimize the coupling efficiency and the angle of the intensity distribution of the light source to be used. The collimator lens 7 can change the characteristics of a focus error signal, which will be described later. The range (servo pull-in range) driven by the servo mechanism for displacing the lens 3 can be optimized.

  The astigmatism generation means 8 is disposed between the collimator lens 7 and the light receiving unit 9 and generates astigmatism in the reflected light from the surface to be measured 101 collected by the collimator lens 7. The astigmatism generating means 8 is composed of an optical component including a cylindrical surface disposed in the optical path of the reflected light from the collimator lens 7 to the light receiving unit 9. As the astigmatism generating means, a cylindrical lens is generally used, but in this embodiment, a multi-lens that combines a spherical surface and a cylindrical surface is employed. As a result, astigmatism can be generated and the output signal waveform can be adjusted, and the number of parts can be reduced.

  Note that the astigmatism generating means 8 of the present embodiment can also be configured by a transparent substrate disposed obliquely in the optical path of the reflected light from the collimator lens 7 to the light receiving unit 9.

  The light receiving unit 9 detects the amount of reflected light in which astigmatism is generated by the astigmatism generating means 8. The light receiving unit 9 includes four light receiving elements 21 to 24 arranged on a plane orthogonal to the optical axis of the reflected light (see FIG. 2). The irradiation images of the reflected light incident on these four light receiving elements 21 to 24 change depending on the distance from the objective lens 3 to the measured surface 101 because astigmatism occurs in the reflected light. The shape of this irradiation image (irradiation spot) will be described later.

  The incident light beam diameter adjusting means 12 is disposed in the optical path of the reflected light from the objective lens 3 to the light receiving unit 9 and adjusts the light beam diameter of the reflected light from the measurement surface incident on the light receiving unit 9. In the present embodiment, the incident beam diameter adjusting means 12 is disposed between the collimator lens 7 and the light receiving unit 9 and in the immediate vicinity of the light receiving unit 9. The incident light beam diameter adjusting means 12 is preferably arranged on or near the light receiving unit in order to accurately adjust the size and position of the light beam diameter irradiated on the light receiving unit. The incident light beam diameter adjusting means 12 of the present embodiment is constituted by an aperture 13 that blocks the reflected light from the surface to be measured incident on the light receiving unit 9. The aperture 13 has a frame portion 13 a that blocks the reflected light from the measurement surface incident on the light receiving unit 9, and an opening 13 b that allows the reflected light from the measurement surface to enter the light receiving unit 9. When the aperture 13 is used, when the distance between the surface to be measured and the objective lens is greatly deviated and the diameter of the light beam irradiated onto the light receiving portion increases, the light that has fallen on the upper portion of the aperture 13a does not enter the light receiving portion. Compared to the case where the signal decreases and no aperture is used, the rising edge of the SUM signal can be shortened.

  The aperture 13 may be a fixed type or a variable type. Since the aperture of the variable aperture can be changed by a shutter function or the like, the diameter of the reflected light beam from the surface to be measured incident on the light receiving unit 9 according to the specifications such as the environment and operating conditions of the displacement detection device. Can be adjusted.

  The position information generation unit 10 generates position information of the measured surface 101 using the focus error signal and the SUM signal obtained by the light receiving unit 9. The position information generator 10 reads a focus error signal generator and a SUM signal generator (not shown), a servo control circuit (not shown), the actuator, the linear scale, and the scale of the linear scale. It comprises a detection head (not shown).

  When the value of the focus error signal is “0”, the focal position of the emitted light condensed by the objective lens 3 is the light from the collimator lens 7 as the condensing means, the astigmatism generating means 8, and the light receiving unit 9. Determined by axial position. In the present embodiment, the collimator lens 7 generates astigmatism so that the value of the focus error signal becomes “0” when the focus position of the emitted light condensed by the objective lens 3 is on the measurement surface 101. The position of the means 8 or the light receiving unit 9 on the optical axis is set.

Next, the measurement of the displacement amount of the measurement target surface 101 by the displacement detection device 1 will be described with reference to FIGS.
FIG. 2 is an explanatory diagram showing an example of an irradiation image irradiated on the light receiving unit 9 of the displacement detection device 1. FIG. 3 is a diagram illustrating the characteristics of the focus error signal and the SUM signal obtained from the light amount detected by the light receiving unit 9.

  As shown in FIG. 1, the emitted light emitted from the light source 2 is converted into parallel light by the collimator lens 6 and reflected by the polarization beam splitter 15. The outgoing light from the light source 2 reflected by the polarization beam splitter 15 passes through the phase plate 16 to become circularly polarized light, is reflected by the mirror 5 and guided to the objective lens 3. Thereafter, the emitted light is condensed toward the measurement surface 101 by the objective lens 3 and imaged on the measurement surface 101.

  The reflected light reflected by the measurement surface 101 is reflected by the mirror 5 and guided to the phase plate 16. The reflected light that has passed through the phase plate 16 becomes linearly polarized light that is orthogonal to the outgoing light before passing through the phase plate 16 and passes through the polarization beam splitter 15. Thereafter, the reflected light is collected by the collimator lens 7, is in a state in which astigmatism is generated by the astigmatism generation means 8, passes through the inside of the incident light beam diameter adjustment means 12, and is irradiated to the light receiving unit 9.

As illustrated in FIG. 2, the light receiving unit 9 includes four light receiving elements 21 to 24 arranged on a plane orthogonal to the optical axis of the reflected light. These four light receiving elements 21 to 24 are arranged at a predetermined interval around the optical axis of the reflected light, and the light receiving element 21 and the light receiving element 23 face each other with the optical axis of the reflected light interposed therebetween. The light receiving element 22 and the light receiving element 24 face each other across the optical axis of the reflected light.

  The region (irradiation spot P) in which the reflected light in which astigmatism occurs is irradiated onto the four light receiving elements 21 to 24 (irradiation spot P) varies depending on the distance from the objective lens 3 to the measured surface 101. In the present embodiment, when the focal position f of the emitted light collected by the objective lens 3 is on the measurement surface 101, the irradiation spot becomes a small circle (see FIG. 2D). Here, the position of the objective lens 3 when the irradiation spot becomes a small circle is defined as a reference position.

  In the present embodiment, when the objective lens 3 is closer to the measurement surface 101 than the reference position, the irradiation spot becomes an ellipse extending toward the light receiving elements 22 and 24 (see FIG. 2C). When the objective lens 3 further approaches the surface to be measured 101, the irradiation spot becomes circular on the light receiving elements 21, 22, 23, and 24 that are light receiving portions (see FIG. 2B), and the objective lens 3 is measured. As the surface 101 is further approached, the irradiation spot becomes more blurred and larger than the light receiving unit. (See FIG. 2 (a)). When the objective lens 3 moves away from the measurement surface 101 from the reference position, the irradiation spot becomes an ellipse extending toward the light receiving elements 21 and 23 (see FIG. 2E), and the objective lens 3 is covered. As the distance from the measurement surface 101 further increases, the irradiation spot becomes a large circle on the light receiving elements 21, 22, 23, and 24 (see FIG. 2F), and when the objective lens 3 is further away from the measurement surface 101, the irradiation spot is irradiated. The spot is further blurred and larger than the light receiving portion. (See FIG. 2 (g)).

  Each of the light receiving elements 21 to 24 converts the detected light into electric energy (photoelectric conversion), generates an output signal, and outputs the output signal to the focus error signal generation unit and the SUM signal generation unit of the position information generation unit 10.

Focus error signal generating unit generates a focus error signal S _FE from the output signal of the light receiving elements 21 to 24 is output. The focus error signal _SFE represents a shift in the optical axis direction with respect to the reference position of the objective lens 3.

When the output signals of the light receiving elements 21, 22, 23, 24 are output signals A, B, C, D, the focus error signal _SFE is calculated by the following equation.
(Equation 1) _SFE = (A + C)-(B + D)

SUM signal generating unit generates a SUM signal _{S SUM} from the output signal of the light receiving elements 21 to 24 is output. The SUM signal _SSUM represents the total amount of reflected light from the surface to be measured that is incident on the light receiving elements 21, 22, 23, and 24.

Assuming that the output signals of the light receiving elements 21, 22, 23, 24 are output signals A, B, C, D, the SUM signal _SSUM is calculated by the following equation.
(Expression 2) S _SUM = (A + C) + (B + D)

Characteristics of the calculated SUM signal _{S SUM} by the calculated focus error signal _{S FE} and was (Equation 2) by the above equation (1) is as shown in FIG.

In the characteristic of the focus error signal _SFE indicated by the solid line in FIG. 3, the origin O indicates the reference position of the objective lens 3.
The focus error signal generation unit of the position information generation unit 10 performs analog-to-digital conversion on the generated focus error signal _SFE and outputs it to the servo control circuit. The servo control circuit outputs a drive signal such that the value of the focus error signal SFE is “0” to the actuator, and performs drive control of the actuator. Thereby, the linear scale fixed to the lens holding part moves in the optical axis direction of the objective lens 3. Then, when the detection head reads the scale of the linear scale, the displacement amount of the measured surface 101 is measured.

In FIG. 3, the characteristic of the SUM signal when the conventional incident beam diameter adjusting means is not used is indicated by a dotted line.
In the characteristics of the SUM signal _SSUM shown by the dotted line in FIG. 3, when the light beam diameter on the light receiving surface of the reflected light from the surface to be measured is reduced and the amount of light incident on each light receiving element 21, 22, 23, 24 is increased. , rises SUM signal as shown in _{S 1.} On the other hand, when the amount of light incident on the beam diameter becomes large and the light receiving elements 21, 22, 23, 24 on the light receiving surface of the light reflected from the measured surface is reduced, it falls SUM signal as shown in S _3. Leading edge S ₂ of the SUM signal, the SUM signal is formed until the fall from the rise. When the irradiation spot is in the state of FIGS. 2A and 2G, the diameter of the light beam reflected from the surface to be measured is very large, and the amount of light incident on each light receiving element 21, 22, 23, 24. Is so small that the value of the SUM signal S _SUM is “almost 0”.

FIG. 4 is a plan view showing a relative positional relationship between an aperture which is an incident light beam diameter adjusting unit and a light receiving element according to the embodiment of the displacement detection device.
In the present embodiment, the aperture 13 that covers the light receiving elements 21, 22, 23, 24 is used as the incident light beam diameter adjusting means. An opening 13 b is formed at the center of the aperture 13. The size of the opening 13b is appropriately set according to the specification form of the displacement detection device.

In FIG. 3, the characteristic of the SUM signal _SSUM when the aperture 13 is used is indicated by a solid line.
When the irradiation spot is in the state shown in FIGS. 2A and 2B, most of the reflected light from the surface to be measured is blocked by the frame portion 13a of the aperture 13, so that the incident beam diameter adjusting means is not used. , The total amount of reflected light from the measurement surface incident on the light receiving element through the opening 13b is reduced, the value of the SUM signal _SSUM is reduced, and the reflected light from the measurement surface incident on the aperture 13 is reduced. As the magnitude increases, the value of the SUM signal _SSUM becomes closer to “0”.

  When the irradiation spot is in the state shown in FIGS. 2C, 2D, and 2E, there is almost no reflected light from the surface to be measured that is blocked by the frame portion 13a of the aperture 13, and most of the measurement is performed. Reflected light from the surface enters the light receiving element through the opening 13b. For this reason, the total amount of reflected light from the measurement surface incident on the light receiving element is large, and the SUM signal rises.

When the irradiation spot is in the state of FIGS. 2 (f) and 2 (g), most of the reflected light from the surface to be measured is blocked by the frame portion 13a of the aperture 13, so that the incident beam diameter adjusting means is not used. , The total amount of reflected light from the measurement surface incident on the light receiving element through the opening 13b is reduced, the value of the SUM signal _SSUM is reduced, and the reflected light from the measurement surface incident on the aperture 13 is reduced. As the magnitude increases, the value of the SUM signal _SSUM becomes closer to “0”.

  As described above, when the aperture 13 is not used, even in the state of FIG. 2B, the total amount of reflected light from the surface to be measured incident on the light receiving element increases, and the SUM signal rises. As in this embodiment, by using the aperture 13, the diameter of the light beam that can be reflected from the surface to be measured can enter the light receiving element can be reduced, the total amount of light can be reduced, and the rise of the SUM signal can be delayed. . Further, when the aperture 13 is not used, even in the state of FIG. 2 (f), the total amount of reflected light from the surface to be measured incident on the light receiving element is large, and the SUM signal remains rising. As in this embodiment, by using the aperture 13, the diameter of the light beam that can be reflected from the surface to be measured can be reduced to reduce the total light amount, and the fall of the SUM signal can be accelerated. it can. Thus, if the rise of the SUM signal is delayed, the fall of the SUM signal is advanced, and the rise interval of the SUM signal is shortened, the range of the focus error signal existing in that interval is also shortened. Therefore, even when a plurality of ringing-like erroneous zero cross points due to stray light or the like are generated in the focus error signal, the number of zero cross points existing in the rising section of the SUM signal is reduced. Thus, the possibility of driving the servo mechanism can be reduced.

  The rising interval of the SUM signal and the falling interval of the SUM signal can be controlled by changing the size of the opening 13b of the aperture 13. That is, when the opening 13b is enlarged, the beam diameter of the reflected light from the measurement surface incident on the light receiving element is increased, the rise of the SUM signal is accelerated, the fall of the SUM signal is delayed, and the SUM signal is delayed. The rising interval of becomes longer. On the other hand, when the opening 13b is made small, the beam diameter of the reflected light from the surface to be measured incident on the light receiving element is reduced, the rise of the SUM signal is delayed, and the fall of the SUM signal is accelerated. The rising interval of becomes shorter. Note that the size of the opening may be changed by a shutter function provided in the aperture 13 or may be replaced with an aperture having a different opening.

  In the displacement detection apparatus of the present embodiment, the incident light beam diameter adjusting means adjusts the amount of reflected light from the surface to be measured that is incident on the light receiving unit, thereby appropriately adjusting the rising section of the SUM signal. It is possible to prevent the servo mechanism from displacing the objective lens based on the zero cross point. As a result, the objective lens can be displaced to an accurate position to perform highly accurate measurement. Even when the specification of the displacement detection device is changed, it is not necessary to replace the light receiving element itself. Furthermore, the processing time until the servo mechanism is driven can be shortened by shortening the rising edge of the SUM signal. In addition, if the rising edge of the SUM signal is lengthened, even if a disturbance such as an impact is applied during the focus servo lock on the surface to be measured and the objective lens moves slightly in the optical axis direction and the focus servo is released, the SUM signal is Since it is difficult to deviate from the signal rising section, the number of processes required for the focus servo return is reduced, and there is an advantage that the time until the focus servo return can be shortened. As described above, it is necessary to optimize the rising section of the SUM signal according to specifications such as a use environment and an operation state.

  The present invention is not limited to the embodiment described above and shown in the drawings, and various modifications can be made without departing from the scope of the invention described in the claims. For example, in the above-described embodiment, the emitted light emitted from the light source 2 is collimated by the collimator lens 6, but the emitted light from the light source 2 that has passed through the collimator lens 6 is divergent light or convergent light. Also good. Further, although the aperture 13 is used as the light amount adjusting means 12, a member such as a mask may be used.

In the embodiment described above, the light source 2 is detachably attached to the housing 11. However, in the displacement detection device of the present invention, the light source 2 is not disposed in the housing 11 but is disposed at a position away from the housing 11 and light is supplied into the housing 11 through an optical fiber. You may do it.
Thereby, the light source 2 used as a heat source can be separated from the casing 11, and a temperature rise in the casing 11 can be prevented. Further, by adopting a structure in which the light source 2 is detachably attached to the optical fiber, the light source 2 can be exchanged at a place away from the housing 11, and the maintainability can be improved.

Moreover, as a displacement detection apparatus of this invention, the light source 2 is arrange | positioned in the position away from the housing | casing 11, and the emitted light from the light source 2 is supplied in the housing | casing 11 through gas, a liquid, or a vacuum space. You may do it.
As a result, the light source 2 serving as a heat source can be separated from the housing 11, and members connected to the housing 11 such as an optical fiber can be removed so that vibration is not transmitted to the housing 11.

In the displacement detection device of the present invention, two light sources having the same wavelength may be provided via a half mirror or the like.
Thereby, since two light sources can emit light alternately, even when one light source cannot be used due to its lifetime, the displacement detection device can be used for a long time by switching to another light source. be able to.

In the above-described embodiment, the light receiving unit 9 directly detects the reflected light in which astigmatism is generated by the astigmatism generating means 8. However, as the displacement detection device of the present invention, the reflected light in which astigmatism has occurred may be guided to the light receiving unit 9 by an optical fiber.
As a result, the installation position of the light receiving unit 9 can be freely set, so that the light receiving unit 9 and the position information generating unit 10 can be arranged close to each other. As a result, the telecommunication distance can be shortened and the response speed can be increased.

Moreover, as a displacement detection apparatus of this invention, you may arrange | position light-scattering bodies, such as cloudy glass, on the optical path between the polarization beam splitter 15 and the light-receiving part 9, for example.
Thereby, a uniform light intensity distribution can be obtained in a cross section perpendicular to the optical axis direction of the reflected light incident on the light receiving unit 9, and the influence of the surface roughness of the measured surface 101 can be further reduced.
In addition, when such a light scatterer is vibrated at, for example, 1 KHz or more and the scattering direction is changed variously, speckles on the light receiving elements 21 to 24 are averaged, and speckle contrast is reduced.

Further, the measurement target surface 101 may be subjected to mirror processing for reflecting the emitted light emitted from the light source 2. Thereby, position information can be obtained from a signal having a high S / N ratio.
In addition, a diffraction grating that reflects light having the same wavelength as the emitted light emitted from the light source 2 may be formed on the measurement object having the measurement surface. For such a surface to be measured, it is possible to configure a displacement detection device that combines the displacement detection device of the above-described embodiment and a so-called linear scale that receives the diffracted light and detects the position in the surface direction. preferable. Thereby, displacement detection in a three-dimensional direction is possible.

  When a diffraction grating is formed on the object to be measured, a reflection film that reflects light emitted from the light source 2 may be formed on the surface of the diffraction grating to form a surface to be measured. The displacement detection device of the above-described embodiment detects displacement in the height direction by detecting reflected light from the surface to be measured formed by the reflective film. At this time, since the emitted light emitted from the light source 2 is not diffracted by the diffraction grating, accurate displacement detection can be performed. The linear scale detects diffracted light and the like by using a light source that passes through the reflective film.

  Further, the surface to be measured formed by the reflective film may be formed on the base side of the diffraction grating. In this case, the light emitted from the light source 2 passes through the material forming the diffraction grating, and the light used for the linear scale becomes diffracted light by the diffraction grating.

  Further, in the displacement detection device of the present invention, the diameter of the emitted light (beam) on the measured surface is assumed as a state in which the focal point of the emitted light collected by the objective lens is imaged in front of or behind the measured surface. The diameter may be a predetermined size. Thereby, it can suppress detecting the surface roughness of a to-be-measured surface, dirt, fine dust, etc. as a displacement amount. The diameter of the emitted light on the surface to be measured is desirably 50 μm or more.

  DESCRIPTION OF SYMBOLS 1 ... Position detection apparatus, 2 ... Light source, 3 ... Objective lens, 4 ... Separation optical system, 5 ... Mirror, 6 ... Collimator lens, 7 ... Collimator lens (collection) Light means), 8 astigmatism generating means, 9 light receiving part, 10 position information generating part, 11 casing, 12 light incident beam diameter adjusting means, 13. Aperture, 13a ... frame, 13b ... opening, 15 ... polarizing beam splitter, 16 ... phase plate, 21, 22, 23, 24 ... light receiving element, 101 ... covered Measuring surface, P ... irradiation spot

Claims (1)

A light source;
An objective lens that focuses the emitted light from the light source toward the surface to be measured;
A separation optical system that separates an optical path of reflected light from the measurement surface from an optical path of light emitted from the light source;
Condensing means for condensing the reflected light separated from the optical path of the outgoing light by the separation optical system;
Astigmatism generating means for generating astigmatism in the reflected light collected by the light collecting means;
A light receiving unit for detecting the amount of the reflected light in which astigmatism is generated by the astigmatism generating unit;
A surface to be measured which is on the optical path of the reflected light and which is provided between the objective lens and the light receiving unit and between the astigmatism generating means and the light receiving unit. Incident light beam diameter adjusting means for adjusting the light beam diameter of the reflected light from
A position information generation unit that generates position information of the surface to be measured using a focus error signal obtained from a light amount detected by the light receiving unit, and
The incident light beam diameter adjusting means includes a rectangular frame portion that blocks light reflected from the surface to be measured incident on the light receiving portion, and the frame portion for causing the reflected light from the surface to be measured to enter the light receiving portion. And a rectangular opening provided at the center of the displacement detecting device.

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