JP6907064B2 - Displacement detector - Google Patents

Description

The present invention relates to a displacement detection device that detects the thickness and position of an object to be measured by a non-contact sensor using light.

Conventionally, a displacement detection device has been widely used as a device 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 focused on the surface to be measured by the objective lens, the reflected light reflected on the surface to be measured is focused by the astigmatic optical element, and is incident on the light receiving element. The focus signal is generated by the astigmatism method.

Then, the actuator is driven using the generated focus signal, and the objective lens is displaced so that the focal position of the objective lens is 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 integrally attached to the objective lens via the connecting member (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-300236

However, in the displacement detection device described in Patent Document 1, the objective lens is moved up and down in the optical axis direction by a drive mechanism such as an actuator using a magnet and a coil. Therefore, the mechanical response frequency of the vertical movement of the objective lens is limited by the structure and mass of the actuator. As a result, the technique described in Patent Document 1 has a problem that a high response speed cannot be obtained.

Further, in order to measure the thickness of the object to be measured, it is necessary to acquire the position information on the front surface side and the position information on the back surface side of the object to be measured. Therefore, in the displacement detection device described in Patent Document 1, it is necessary to drive the actuators when acquiring the position information on the front surface side and the position information on the back surface side, respectively. As a result, the displacement detection device described in Patent Document 1 has a problem that a measurement error occurs due to vibration when driving the actuator, and the thickness of the object to be measured cannot be measured with high accuracy. rice field.

An object of the present invention is to provide a displacement detection device capable of measuring the distance between two surfaces facing each other in the height direction of an object to be measured with high accuracy and capable of high-speed and stable measurement.

In order to solve the above problems and achieve the object of the present invention, the displacement detection device of the present invention includes a light source, an objective lens, a separation optical system, a condenser lens, an astigmatism generating portion, and a split optical system. A first light receiving unit, a second light receiving unit, a first absolute position calculation unit, a second absolute position calculation unit, and a comparer are provided.
The objective lens focuses the light emitted from the light source toward the object to be measured. The separation optical system uses the optical path of the first reflected light reflected by the first surface of the object to be measured and the second reflected light reflected by the second surface facing the first surface of the object to be measured as a light source. It is separated from the optical path of the light emitted from. The condenser lens collects the first reflected light and the second reflected light separated from the optical path of the light emitted from the light source by the separation optical system. The astigmatism generating unit generates astigmatism in the first reflected light and the second reflected light collected by the condenser lens. The split optical system divides the light in which the first reflected light and the second reflected light in which astigmatism is generated by the astigmatism generating portion overlap into two. The first light receiving unit receives the first reflected light from the light divided into two by the split optical system. The second light receiving unit receives the second reflected light from the light divided into two by the split optical system.
The height of the first absolute position calculation unit is the height in which the first surface and the second surface of the first surface of the object to be measured face each other based on the amount of the first reflected light received by the first light receiving unit. Calculate the absolute position information of the direction. The second absolute position calculation unit calculates the absolute position information in the height direction on the second surface of the object to be measured based on the amount of the second reflected light received by the second light receiving unit. The comparator is the first in the object to be measured from the difference between the absolute position information of the first surface calculated by the first absolute position calculation unit and the absolute position information of the second surface calculated by the second absolute position calculation unit. Calculate the distance between the surface and the second surface in the height direction. Then, the first absolute position calculation unit and the second absolute position calculation unit calculate the absolute position information of the first surface and the absolute position information of the second surface in synchronization with each other.

Further, other displacement detection devices of the present invention include a light source, an objective lens, a separation optical system, a condenser lens, a split optical system, a first knife edge, a second knife edge, and a first light receiving unit. A second light receiving unit, a first absolute position calculation unit, a second absolute position calculation unit, and a comparator are provided.
The objective lens focuses the light emitted from the light source toward the object to be measured. The separation optical system uses the optical path of the first reflected light reflected by the first surface of the object to be measured and the second reflected light reflected by the second surface facing the first surface of the object to be measured as a light source. It is separated from the optical path of the light emitted from. The condenser lens collects the first reflected light and the second reflected light separated from the optical path of the light emitted from the light source by the separation optical system. The dividing optical system divides the light in which the first reflected light and the second reflected light collected by the condensing lens overlap into two. The first knife edge blocks a part of the light divided into two by the dividing optical system. The second knife edge blocks a part of the remaining light of the light divided into two by the split optical system.
The height of the first absolute position calculation unit is the height in which the first surface and the second surface of the first surface of the object to be measured face each other based on the amount of the first reflected light received by the first light receiving unit. Calculate the absolute position information of the direction. The second absolute position calculation unit calculates the absolute position information in the height direction on the second surface of the object to be measured based on the amount of the second reflected light received by the second light receiving unit. The comparator is the first in the object to be measured from the difference between the absolute position information of the first surface calculated by the first absolute position calculation unit and the absolute position information of the second surface calculated by the second absolute position calculation unit. Calculate the distance between the surface and the second surface in the height direction. Then, the first absolute position calculation unit and the second absolute position calculation unit calculate the absolute position information of the first surface and the absolute position information of the second surface in synchronization with each other.

According to the displacement detection device of the present invention, the distance between two surfaces facing each other in the height direction of the object to be measured can be measured with high accuracy, and high-speed and stable measurement becomes possible.

It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the thickness detection part of the displacement detection apparatus which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the state of the light which irradiates the object to be measured in the displacement detection apparatus which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the positional relationship of the 1st light receiving part and the 2nd light receiving part in the displacement detection apparatus which concerns on 1st Embodiment of this invention. The characteristics of the focus signal obtained from the amount of light detected by the first light receiving unit in the displacement detection device according to the first embodiment of the present invention, and the irradiation image irradiated on the light receiving surface of the first light receiving unit. It is explanatory drawing which shows an example. The characteristics of the focus signal obtained from the amount of light detected by the second light receiving unit in the displacement detection device according to the first embodiment of the present invention, and the irradiation image irradiated on the light receiving surface of the second light receiving unit. It is explanatory drawing which shows an example. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 2nd Embodiment of this invention. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the thickness detection part of the displacement detection apparatus which concerns on 3rd Embodiment of this invention. It is explanatory drawing which shows the example of the irradiation image which irradiates the light receiving surface of the 1st light receiving part and the 2nd light receiving part in the displacement detection apparatus which concerns on 3rd Embodiment of this invention. It is explanatory drawing which shows the characteristic of the focus signal obtained from the amount of light detected by the 1st light receiving part and the 2nd light receiving part in the displacement detection apparatus which concerns on 3rd Embodiment of this invention. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 4th Embodiment of this invention. It is explanatory drawing which shows the example of the irradiation image which irradiates the light receiving surface of the 1st light receiving side light guide member and the 2nd light receiving side light guide member in the displacement detection apparatus which concerns on 4th Embodiment of this invention. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 5th Embodiment of this invention. It is a schematic block diagram which shows the structure of the displacement detection apparatus which concerns on 6th Embodiment of this invention.

Hereinafter, examples of embodiments of the displacement detection device of the present invention will be described with reference to FIGS. 1 to 15. The common members in each figure are designated by the same reference numerals. Moreover, the present invention is not limited to the following forms.
Further, the various lenses described in the following description may be a single lens or a lens group.

1. 1. First Embodiment Example First, the configuration of the first embodiment example (hereinafter, referred to as “this example”) of the displacement detection device of the present invention will be described with reference to FIGS. 1 to 6.

1-1. Configuration Example of Displacement Detection Device FIG. 1 is a schematic configuration diagram showing a configuration of a displacement detection device.
As shown in FIG. 1, the displacement detection device 1 has a head 2 facing the object T to be measured and a thickness detecting unit 3 for calculating the thickness A1 of the object T to be measured. The head 2 includes a light source 11, a first lens 12, a separation optical system 13, an objective lens 14, a second lens 15, an astigmatism generating unit 16, a split optical system 17, and a first light receiving unit. It has 18 and a second light receiving unit 19. The thickness detection unit 3 may be housed in the head 2, or may be arranged in a portable information processing terminal or a PC (personal computer) provided outside the head 2.

The object T to be measured is formed in a substantially flat plate shape by a material having a property of transmitting light. The object T to be measured has a front surface T1 showing a first surface and a back surface T2 showing a second surface facing the front surface T1. Then, the displacement detection device 1 detects the length in the height direction Z in which the front surface T1 and the back surface T2 of the object to be measured T face each other, that is, the thickness A1 of the object to be measured T.

Examples of the light source 11 include a semiconductor laser diode, a superluminescence diode, a gas laser, a solid-state laser, and a light emitting diode. The light source 11 is detachably attached to the head 2. By attaching the light source 11 to the head 2 detachably, the deteriorated light source 11 can be replaced with a new light source 11 without removing the head 2 from the installation location. As a result, there is no concern that the installation position of the head 2 will shift each time the light source 11 is replaced, which is advantageous when the displacement detection device 1 is used for a measurement or manufacturing device that requires reliability.

The first lens 12 is arranged on the exit side of the light source 11. The first lens 12 is composed of, for example, a collimating lens or the like. The first lens 12 collimates the light L emitted from the light source 11 with parallel light. The light L collimated with the parallel light by the first lens 12 is incident on the separation optical system 13.

The separation optical system 13 is composed of, for example, a beam splitter, a half mirror, and the like. The separation optical system 13 transmits the light L emitted from the light source 11. Further, the separation optical system 13 reflects the first reflected light L1 reflected by the front surface T1 of the object T to be measured and the second reflected light L2 reflected by the back surface T2 of the object T to be measured. That is, the separation optical system 13 separates the optical paths of the first reflected light L1 and the second reflected light L2 from the optical paths of the light L emitted from the light source 11.

An objective lens 14 is arranged between the separation optical system 13 and the object T to be measured. The objective lens 14 collects the light L emitted from the light source 11 and transmitted through the separation optical system 13 toward the object T to be measured. The objective lens 14 is fixed to the head 2 with its focal position f1 aligned in the object T to be measured or in the vicinity of the object T to be measured. As a result, since the objective lens 14 is fixed, it is possible to prevent unnecessary vibration from being generated in the objective lens 14.

In the displacement detection device 1 of this example, an example of fixing the objective lens 14 to the head 2 has been described, but the present invention is not limited to this. For example, the objective lens 14 may be supported so as to be movable in the optical axis direction of the objective lens 14 by using a lens holding portion (not shown). As a result, when the object T to be measured frequently deviates from the focal position f1 of the objective lens 14, only the objective lens 14 can be moved without moving the entire head 2. Then, the objective lens 14 is fixed at a predetermined position by the lens holding portion in a state where the focal position f1 of the objective lens 14 is aligned with the inside of the object to be measured T or the vicinity of the object to be measured T. Therefore, the objective lens 14 is fixed at a predetermined position when detecting the thickness A1 of the object T to be measured.

Further, the first reflected light L1 reflected by the front surface T1 of the object T to be measured and the second reflected light L2 reflected by the back surface T2 of the object T to be measured are collimated with the parallel light again by the objective lens 14. The first reflected light L1 and the second reflected light L2 are incident on the separation optical system 13 again while overlapping, and are reflected by the separation optical system 13 toward the second lens 15.

Like the first lens 12, the second lens 15 showing an example of the condenser lens is composed of a collimator lens and the like. The second lens 15 collects the first reflected light L1 and the second reflected light L2 reflected by the separation optical system 13 toward the astigmatism generating unit 16 and the split optical system 17.

The first lens 12, the objective lens 14, and the second lens 15 may be subjected to achromatic measures (chromatic aberration correction) that make it difficult for the focal length to fluctuate due to the wavelength fluctuation of the light source 11. As a result, it is not necessary to monitor the wavelength and temperature of the light source 11, and it is not necessary to correct the measured value obtained by measuring the thickness A1 of the object T to be measured.

The astigmatism generating unit 16 is arranged between the second lens 15 and the split optical system 17. The astigmatism generating unit 16 generates astigmatism in the first reflected light L1 and the second reflected light L2 collected by the second lens 15. The astigmatism generating unit 16 is composed of, for example, a transparent substrate obliquely arranged in the optical path of the first reflected light L1 and the second reflected light L2 emitted from the second lens 15.

The astigmatism generating unit 16 is not limited to a transparent substrate diagonally arranged in the optical path, and is not limited to, for example, a cylindrical lens, a multi-lens in which a spherical surface and a cylindrical surface are combined, and various other optical components. Can be applied.

The split optical system 17 is composed of, for example, a beam splitter, a half mirror, and the like. The split optical system 17 divides the light that has passed through the astigmatism generating portion 16 into two. The light reflected by the split optical system 17 is incident on the first light receiving unit 18, and the light transmitted through the split optical system 17 is incident on the second light receiving unit 19. Further, the distance h1 between the first light receiving unit 18 and the split optical system 17 (see FIG. 3) and the distance h2 between the second light receiving unit 19 and the split optical system 17 (see FIG. 3) are set to different lengths. ing. The detailed positional relationship between the first light receiving unit 18 and the second light receiving unit 19 will be described later.

At least one of the first light receiving unit 18 and the second light receiving unit 19 is movably supported along the optical axis direction of the light emitted from the split optical system 17. Then, the positions of the first light receiving unit 18 and the second light receiving unit 19 can be adjusted according to the reference thickness of the object T to be measured for thickness measurement.

The first light receiving unit 18 showing the first light receiving unit detects the amount of light of the first reflected light L1 that is reflected by the surface T1 of the object T to be measured and the astigmatism generating unit 16 generates astigmatism. The first light receiving unit 18 is composed of four light receiving elements 31, 32, 33, and 34 arranged on a plane orthogonal to the optical axis of the first reflected light L1 (see FIGS. 2 and 5B). The shape of the irradiation image (irradiation spot) P1 that irradiates the four light receiving elements 31, 32, 33, and 34 will be described later.

The second light receiving unit 19 showing the second light receiving unit detects the amount of light of the second reflected light L2 that is reflected by the back surface T2 of the object T to be measured and the astigmatism generating unit 16 generates astigmatism. The second light receiving unit 19 is composed of four light receiving elements 41, 42, 43, 44 arranged on a plane orthogonal to the optical axis of the second reflected light L2 (see FIGS. 2 and 6B). The shape of the irradiation image (irradiation spot) P2 irradiated on the four light receiving elements 41, 42, 43, 55 will be described later.

The first light receiving unit 18 and the second light receiving unit 19 are connected to the thickness detecting unit 3. Then, the first light receiving unit 18 and the second light receiving unit 19 output the obtained focus signal to the thickness detecting unit 3. The thickness detection unit 3 calculates the thickness A1 of the object T to be measured by using the focus signals obtained by the first light receiving unit 18 and the second light receiving unit 19.

FIG. 2 is a block diagram showing a thickness detection unit 3.
As shown in FIGS. 1 and 2, the thickness detection unit 3 includes a first absolute position calculation unit 21 connected to the first light receiving unit 18 and a second absolute position calculation unit connected to the second light receiving unit 19. It has 22, a first absolute position calculation unit 21, and a comparator 23 connected to the second absolute position calculation unit 22.

As shown in FIG. 2, the first absolute position calculator 21 includes a first adder 51, a second adder 52, a differential amplifier 53, and an absolute position calculator 54. The first adder 51 is connected to the first light receiving element 31 of the first light receiving unit 18 and the second light receiving element 32. Then, the first adder 51 adds the signals photoelectrically converted by the first light receiving element 31 and the second light receiving element 32. The second adder 52 is connected to the third light receiving element 33 of the first light receiving unit 18 and the fourth light receiving element 34. Then, the second adder 52 adds the signals photoelectrically converted by the third light receiving element 33 and the fourth light receiving element 34.

The differential amplifier 53 is connected to the first adder 51 and the second adder 52. The differential amplifier 53 differentially amplifies the signals added by the first adder 51 and the second adder 52. The differential amplifier 53 is connected to the absolute position calculator 54. The absolute position calculator 54 calculates the absolute position information in the height direction Z on the surface T1 of the object T to be measured from the signal calculated by the differential amplifier 53.

The second absolute position calculation unit 22 has a first adder 61, a second adder 62, a differential amplifier 63, and an absolute position calculation unit 64, similarly to the first absolute position calculation unit 21. There is. The first adder 61 is connected to the first light receiving element 41 of the second light receiving unit 19 and the second light receiving element 42. Then, the first adder 61 adds the signals photoelectrically converted by the first light receiving element 41 and the second light receiving element 42. The second adder 62 is connected to the third light receiving element 43 of the second light receiving unit 19 and the fourth light receiving element 44. Then, the second adder 62 adds the signals photoelectrically converted by the third light receiving element 43 and the fourth light receiving element 44.

The differential amplifier 63 is connected to the first adder 61 and the second adder 62. The differential amplifier 63 differentially amplifies the signals added by the first adder 61 and the second adder 62. The differential amplifier 63 is connected to the absolute position calculator 64. The absolute position calculator 64 calculates the absolute position information in the height direction Z on the back surface T2 of the object T to be measured from the signal calculated by the differential amplifier 63.

The detailed calculation method of the absolute position information in the first absolute position calculation unit 21 and the second absolute position calculation unit 22 will be described later.

The comparator 23 is connected to the absolute position calculator 54 of the first absolute position calculator 21 and the absolute position calculator 64 of the second absolute position calculator 22. The comparator 23 is the thickness of the object T to be measured from the difference between the absolute position information of the front surface T1 calculated by the first absolute position calculation unit 21 and the absolute position information of the back surface T2 calculated by the second absolute position calculation unit 22. A1 is calculated and the calculated thickness A1 is output.

1-2. Positional relationship between the first light receiving unit and the second light receiving unit Next, the detailed positional relationship between the first light receiving unit 18 and the second light receiving unit 19 will be described with reference to FIGS. 3 and 4.
FIG. 3 is an explanatory diagram showing a state of light irradiated to the object T to be measured, and FIG. 4 is an explanatory diagram showing a positional relationship between the first light receiving unit 18 and the second light receiving unit 19.

First, as shown in FIG. 3, the object T to be measured reflects the light L indicated by the irradiated solid line on the front surface T1 and the light L transmitted through the front surface T1 on the back surface T2. Therefore, the light L applied to the object T to be measured is reflected by the first reflected light L1 indicated by the alternate long and short dash line reflected by the front surface T1 indicating the first surface and the second reflected light L indicated by the back surface T2 indicating the second surface. It becomes the second reflected light L2 indicated by the dotted line. Further, as described above, the focal position f1 of the objective lens 14 is set so as to be in the object T to be measured or in the vicinity of the object T to be measured. Therefore, the wavefronts of the first reflected light L1 and the second reflected light L2 are slightly different due to the difference in length of the thickness A1 of the object T to be measured.

As shown in FIG. 4, in the first light receiving unit 18, the optical path length from the second lens 15 to the light receiving surface thereof is set to the length that the first reflected light L1 reflected on the surface T1 collects on the light receiving surface. It is set. Therefore, the irradiation image P1 of the first reflected light L1 is formed on the light receiving surface of the first light receiving unit 18. Further, the optical path length from the second lens 15 to the light receiving surface of the first light receiving unit 18 is set to the length at which the second reflected light L2 reflected by the back surface T2 is diverged. Therefore, the optical path length from the second lens 15 to the light receiving surface of the first light receiving unit 18 is within a range in which the focus signal of the first reflected light L1 can be detected by the first light receiving unit 18, and the second reflected light. The focus signal of L2 is set in an undetectable range.

On the other hand, in the second light receiving unit 19, the optical path length from the second lens 15 to the light receiving surface thereof is set at a position where the second reflected light L2 reflected by the back surface T2 is focused on the light receiving surface. Have been placed. Therefore, the irradiation image P2 of the second reflected light L2 is formed on the light receiving surface of the second light receiving unit 19. Further, the optical path length from the second lens 15 to the light receiving surface of the second light receiving unit 19 is set to the length at which the first reflected light L1 reflected by the surface T1 is diverged. Therefore, the optical path length from the second lens 15 to the light receiving surface of the second light receiving unit 19 is within a range in which the focus signal of the second reflected light L2 can be detected by the second light receiving unit 19, and the first reflected light. The focus signal of L1 is set in an undetectable range.

Here, the optical path lengths from the second lens 15 to the split optical system 17 in the first reflected light L1 and the second reflected light L2 are equal. Therefore, by adjusting the distance h1 from the light receiving surface of the first light receiving unit 18 to the split optical system 17 and the distance h2 from the light receiving surface of the second light receiving unit 19 to the split optical system 17, the first light receiving is received. The optical path lengths to the unit 18 and the second light receiving unit 19 are set in the above-mentioned range. The distance h1 from the light receiving surface of the first light receiving unit 18 to the split optical system 17 and the split optical system from the light receiving surface of the second light receiving unit 19 are different due to the difference in the thickness A1 of the object T to be measured. The intervals h2 up to 17 have different lengths.

1-3. Calculation method of absolute position information of the first absolute position calculation unit and the second absolute position calculation unit Next, referring to FIGS. 5 and 6, the absolute position information of the first absolute position calculation unit and the second absolute position calculation unit The calculation method of is described.

FIG. 5A shows the characteristics of the focus signal obtained by the first light receiving unit 18, and FIG. 5B shows an example of an irradiation image applied to the light receiving surface of the first light receiving unit 18. The horizontal axis of FIG. 5A indicates the position of the object T to be measured in the height direction Z orthogonal to the front surface T1 and the back surface T2, and the vertical axis is output from the differential amplifier 53 of the first absolute position calculation unit 21. Shows the focus signal.

As shown in FIG. 5B, in the first light receiving unit 18, the first light receiving element 31, the second light receiving element 32, the third light receiving element 33, and the fourth light receiving element 34 are the optical axes of the first reflected light L1. They are arranged around them at predetermined intervals. The first light receiving element 31 and the second light receiving element 32 face each other with the optical axis of the first reflected light L1 interposed therebetween, and the third light receiving element 33 and the fourth light receiving element 34 are the optical axes of the first reflected light L1. Are facing each other across.

As described above, in the first light receiving unit 18, the optical path length from the second lens 15 to the light receiving surface thereof is such that the first reflected light L1 reflected by the surface T1 is focused on the light receiving surface. It is arranged at a position where the second reflected light L2 reflected by the back surface T2 is diverged. Therefore, as shown in FIG. 5B, the irradiation image P1 of the first reflected light L1 is formed on the four light receiving elements 31 to 34 of the first light receiving unit 18, and the second reflected light L2 is formed around the irradiation image P1. The irradiation image P2 is irradiated. The irradiation image P2 of the second reflected light L2 has an amount of light that cannot be detected by the four light receiving elements 31 to 34 of the first light receiving unit 18.

Further, astigmatism is added to the first reflected light L1 by the astigmatism generating unit 16. Therefore, when the focal position f1 of the objective lens 14 is located near the middle between the front surface T1 and the back surface T2 of the object T to be measured, the irradiation image P1 becomes the smallest. Then, when the absolute position of the surface T1 in the height direction Z changes, the irradiation image P1 of the first reflected light L1 irradiated to the first light receiving unit 18 is moved to the first light receiving element 31 and the second light receiving element 32 side. It changes to an elongated elliptical shape or an elliptical shape extending toward the third light receiving element 33 and the fourth light receiving element 34.

The output signal output from the first light receiving element 31 is A, the output signal output from the second light receiving element 32 is B, the output signal output from the third light receiving element 33 is C, and the output signal output from the fourth light receiving element 34 is output. the output signal is D that the focus signal S _F which is outputted from the differential amplifier 53 of the first absolute position computing section 21 is represented by the following formula 1.
[Equation 1]
_SF = (A + B)-(C + D)

The characteristics of the focus signal S _F which is outputted from the differential amplifier 53 of the first absolute position computing section 21 is as shown in Figure 5A. The value of the focus signal S _F shown in FIG. 5A through "0", a region where the change of the focus signals S _F varies linearly with respect to changes in the height direction Z, that is, the area that can be represented by a linear function, the The focus signal detection range S1 of the light receiving unit 18 of 1.

Then, the absolute position calculator 54 of the first absolute position computing unit 21, converts the focus signal S _F which is outputted from the differential amplifier 53, the absolute position information in the height direction Z of the surface T1 of the object T ( (Calculation) and output to the comparator 23.

Next, a method of calculating the absolute position information of the second absolute position calculation unit 22 will be described with reference to FIGS. 6A and 6B.
FIG. 6A shows the characteristics of the focus signal obtained by the second light receiving unit 19, and FIG. 6B shows an example of an irradiation image applied to the light receiving surface of the second light receiving unit 19. The horizontal axis of FIG. 6A indicates the position in the height direction Z, and the vertical axis indicates the focus signal output from the differential amplifier 63 of the second absolute position calculation unit 22.

As shown in FIG. 6B, the second light receiving unit 19 has the same as the first light receiving unit 18, the first light receiving element 41, the second light receiving element 42, the third light receiving element 43, and the fourth light receiving element. 44s are arranged around the optical axis of the second reflected light L2 at predetermined intervals. The first light receiving element 41 and the second light receiving element 42 face each other with the optical axis of the second reflected light L2 interposed therebetween, and the third light receiving element 43 and the fourth light receiving element 44 are the optical axes of the second reflected light L2. Are facing each other across.

As described above, in the second light receiving unit 19, the optical path length from the second lens 15 to the light receiving surface thereof is such that the second reflected light L2 reflected by the back surface T2 is focused on the light receiving surface. It is arranged at a position where the first reflected light L1 reflected by the surface T1 is diverged. Therefore, as shown in FIG. 6B, the irradiation image P2 of the second reflected light L2 is formed on the four light receiving elements 41 to 44 of the second light receiving unit 19, and the first reflected light L1 is formed around the irradiation image P2. The irradiation image P1 is irradiated. The irradiation image P1 of the first reflected light L1 has an amount of light that cannot be detected by the four light receiving elements 41 to 44 of the second light receiving unit 19.

Further, astigmatism is added to the second reflected light L2 by the astigmatism generating unit 16 as in the case of the first reflected light L1. Therefore, when the focal position f1 of the objective lens 14 is located near the middle between the front surface T1 and the back surface T2 of the object T to be measured, the irradiation image P2 becomes the smallest. Then, when the absolute position of the back surface T2 in the height direction Z changes, the irradiation image P2 of the second reflected light L2 irradiated to the second light receiving unit 19 is moved to the first light receiving element 41 and the second light receiving element 42 side. It changes to an elongated elliptical shape or an elliptical shape extending toward the third light receiving element 43 and the fourth light receiving element 44.

The output signal output from the first light receiving element 41 is A, the output signal output from the second light receiving element 42 is B, the output signal output from the third light receiving element 43 is C, and the output signal output from the fourth light receiving element 44 is output. the output signal is D that the focus signal S _F which is outputted from the differential amplifier 63 of the second absolute position computing section 22 is represented by formula 1 described above.

The characteristics of the focus signal S _F which is outputted from the differential amplifier 63 of the second absolute position computing section 22 is as shown in Figure 6A. The value of the focus signal S _F shown in FIG. 6A through "0", a region where the change of the focus signals S _F varies linearly with respect to changes in the height direction Z, that is, the area that can be represented by a linear function, the It is the focus signal detection range S2 of the light receiving unit 19 of 2.

Then, the absolute position calculator 64 of the second absolute position computing section 22, converts the focus signal S _F which is outputted from the differential amplifier 63, the absolute position information in the height direction Z of the rear surface T2 of the measurement object T ( (Calculation) and output to the comparator 23.

1-4. Operation of Displacement Detection Device Next, an operation example of the displacement detection device 1 having the above-described configuration, that is, a measurement example of the thickness A1 of the object T to be measured using the displacement detection device 1 will be described.

First, the mounting positions of the first light receiving portion 18 and the second light receiving portion 19 are adjusted according to the reference thickness of the object T to be measured for thickness measurement. Specifically, at least one of the first light receiving unit 18 and the second light receiving unit 19 is moved along the optical axis direction of the light emitted from the split optical system 17. By adjusting at least one side of the first light receiving portion 18 and the second light receiving portion 19 according to the thickness of the object to be measured T, it is possible to measure the thickness of a wider variety of objects to be measured.

Further, using a high-precision planar mirror, the comparator 23 may calibrate so that the values detected by the first light receiving unit 18 and the second light receiving unit 19 are the same on the same surface. .. Thus, it is possible to calibrate the position at which the value of the focus signal S _F which is outputted at the first absolute position computing section 21 and the second absolute position computing section 22 becomes "0".

Furthermore, the thickness and refractive index using a reference unit that is controlled with high precision, so that the value of Farkas signal S _F of the reflected light reflected at the surface and the back surface is "0", the first light receiving portion At least one of 18 and the second light receiving unit 19 may be adjusted to calibrate the absolute value of the thickness measured by the displacement detection device 1.

As shown in FIGS. 5A and 6A, the irradiated irradiation images P1 and P2 are located within the focus signal detection ranges S1 and S2 at the positions where the first light receiving unit 18 and the second light receiving unit 19 are arranged. It should fit. Therefore, it is not necessary to precisely adjust the focal position f1 of the objective lens 14, the allowable range of mounting accuracy when installing the objective lens 14 can be widened, and the mounting work of the objective lens 14 can be easily performed. ..

Next, the light L is emitted from the light source 11 of the displacement detection device 1 in which the above-mentioned first light receiving unit 18, the second light receiving unit 19, and the thickness detecting unit 3 are initially set, and the object to be measured is emitted from the head 2. Light L is irradiated toward T. The light L applied to the object T to be measured is collimated with parallel light by the first lens 12 and passes through the separation optical system 13. Then, the light L is focused by the objective lens 14 and irradiated to the object T to be measured. As shown in FIGS. 1 and 3, the light L is reflected by the surface T1 of the object T to be measured, and the light L transmitted through the surface T1 of the object T to be measured is reflected by the back surface T2.

The first reflected light L1 reflected by the front surface T1 and the second reflected light L2 reflected by the back surface T2 are collimated with parallel light by the objective lens 14 in an overlapping state and irradiated to the separation optical system 13. The first reflected light L1 and the second reflected light L2 are reflected by the separation optical system 13 and irradiated to the second lens 15. Then, the first reflected light L1 and the second reflected light L2 are condensed by the second lens, transmitted through the astigmatism generating portion 16, and irradiated to the split optical system 17.

The first reflected light L1 and the second reflected light L2 each pass through the astigmatism generating section 16, so that astigmatism is added by the astigmatism generating section 16. Then, the light in which the first reflected light L1 and the second reflected light L2 overlap is divided into two by the split optical system 17, and is received by the first light receiving unit 18 and the second light receiving unit 19.

The first light receiving unit 18 receives the first reflected light L1, and the second light receiving unit 19 receives the second reflected light L2. The first light receiving unit 18 outputs a signal obtained by photoelectrically converting the received first reflected light L1 to the first absolute position calculation unit 21. Further, the second light receiving unit 19 outputs a signal obtained by photoelectrically converting the received second reflected light L2 to the second absolute position calculation unit 22.

Then, the first absolute position calculation unit 21 calculates the absolute position information of the surface T1 of the object to be measured T1 based on the signal from the first light receiving unit 18, that is, the position in the height direction Z, and causes the comparator 23 to calculate the position. Output. The second absolute position calculation unit 22 calculates the absolute position information of the back surface T2 of the object to be measured T2 based on the signal from the second light receiving unit 19, that is, the position in the height direction Z, and outputs the calculation to the comparator 23. .. Since the method of calculating the absolute position information in the first absolute position calculation unit 21 and the second absolute position calculation unit 22 has been described above, the description thereof will be omitted here. The absolute position information calculation operation by the first absolute position calculation unit 21 and the absolute position information calculation operation by the second absolute position calculation unit 22 are performed in synchronization with each other.

Next, the comparator 23 is the object to be measured from the difference between the absolute position information of the front surface T1 calculated by the first absolute position calculation unit 21 and the absolute position information of the back surface T2 calculated by the second absolute position calculation unit 22. The thickness A1 of T is calculated, and the calculated thickness A1 is output. As a result, the measurement operation of the thickness A1 of the object T to be measured using the displacement detection device 1 is completed.

According to the displacement detection device 1 of this example, the light incident on the front surface T1 and the light incident on the back surface T2 of the object T are emitted from the same light source 11, and are emitted from the same first lens 12, the separation optical system 13, and the objective. It has passed through the lens 14. That is, the light incident on the front surface T1 and the light incident on the back surface T2 share the light source 11, the first lens 12, the separation optical system 13, and the objective lens 14.

Further, the first reflected light L1 reflected from the front surface T1 of the object T to be measured and the second reflected light L2 reflected from the back surface T2 are the same objective lens 14, separation optical system 13, second lens 15, astigmatism. It has passed through the aberration generating section 16 and the split optical system 17. That is, the first reflected light L1 and the second reflected light L2 share the objective lens 14, the separation optical system 13, the second lens 15, the astigmatism generating unit 16, and the split optical system 17.

Therefore, vibrations generated in the light source 11, the first lens 12, the separation optical system 13, the objective lens 14, the second lens 15, the non-point aberration generating portion 16 and the split optical system 17, and the error of the installation position are caused by the object T to be measured. It acts equally on the light incident on the front surface T1 and the light incident on the back surface T2, and the first reflected light L1 and the second reflected light L2.

Further, the absolute position information calculation operation of the front surface T1 by the first absolute position calculation unit 21 and the absolute position information calculation operation of the back surface T2 by the second absolute position calculation unit 22 are performed in synchronization with each other. Therefore, when calculating the absolute position information of the front surface T1 and the absolute position information of the back surface T2, it is possible to cancel the influence of vibration by parts such as the light source 11 and the astigmatism generating portion 16 and the error of the installation position, and it is stable. Can be measured.

Further, in order to calculate the thickness A1 of the object to be measured T by calculating the difference between the absolute position information of the front surface T1 and the back surface T2 of the object to be measured T in the comparator 23, the focal position f1 of the objective lens 14 is set to the object to be measured. It is not necessary to match the front surface T1 and the back surface T2 of T. Therefore, in the displacement detection device 1 of this example, the objective lens 14 can be fixed to the head 2 while the object T to be measured is measured, and the actuator or the like that moves the objective lens 14 in the optical axis direction is moved. There is no need to provide a mechanism. As a result, unlike the conventional displacement detection device, mechanical vibration generated when the objective lens 14 is moved does not occur, so that the thickness A1 of the object to be measured T can be measured with high accuracy, and the speed is high. Stable measurement can be performed with.

Further, when the object T to be measured deviates from the irradiation range of the light L from the head 2, the measurement cannot be performed. However, in the displacement detection device 1 of this example, since it is not necessary to adjust the focal position f1 of the objective lens 14, the object T to be measured again is in the irradiation range of the light L, that is, in the vicinity of the focal position f1 of the objective lens 14. When the object T to be measured is placed, the thickness A1 of the object T to be measured can be measured immediately.

Further, the output values of the differential amplifiers 53 and 63 of the first absolute position calculation unit 21 and the second absolute position calculation unit 22 may change due to a change in the reflectance of the object T to be measured. In this case, the first absolute position calculation unit 21 may divide the absolute position information obtained by the first light receiving unit 18 by the total light receiving amount of the first light receiving unit 18. The total light receiving amount is the total amount of light obtained by the four light receiving elements 31, 32, 33, and 34 of the first light receiving unit 18.

Similarly, the second absolute position calculation unit 22 may divide the absolute position information obtained by the second light receiving unit 19 by the total light receiving amount of the second light receiving unit 19. The total light receiving amount is the total amount of light obtained by the four light receiving elements 41, 42, 43, 44 of the second light receiving unit 19. As a result, the influence of the amount of reflected light from the object T to be measured can be suppressed, and the change in the absolute position information calculated by the first absolute position calculation unit 21 and the second absolute position calculation unit 22 due to the change in the amount of light can be suppressed. be able to.

The second reflected light L2 passes through the surface T1 of the object T to be measured and passes through the object T to be measured. Therefore, for example, the coefficient of the refractive index of the object to be measured T may be substituted in advance into the second absolute position calculation unit 22 or the comparator 23 that calculates the absolute position information of the back surface T2. Further, since the actual thickness A1 of the object T to be measured is close to the value divided by the refractive index of the object T to be measured, the thickness A1 calculated by the comparator 23 may be corrected based on the refractive index.

Further, the information output from the comparator 23 can be selected between digital thickness information corresponding to the thickness A1 of the object T to be measured and information obtained by converting the thickness A1 of the object T to be measured into an analog voltage value. You may. If the information output from the comparator 23 is an analog voltage value, the thickness A1 information of the object T to be measured with a data delay can be output at a higher speed.

2. Example of Second Embodiment Next, the displacement detection device according to the second embodiment will be described with reference to FIG. 7.
FIG. 7 is a schematic configuration diagram showing the configuration of the displacement detection device according to the second embodiment.

The displacement detection device 101 according to the second embodiment is different from the displacement detection device 1 according to the first embodiment in the configuration of the separation optical system. Therefore, here, the separation optical system will be described, and the same reference numerals will be given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

As shown in FIG. 7, the displacement detection device 101 includes a head 102 facing the object T to be measured and a thickness detection unit 103 for calculating the thickness. The head 102 includes a light source 11, a first lens 12, a polarizing beam splitter 113, a phase plate 125, an objective lens 14, a second lens 15, an astigmatism generator 16, a split optical system 17, and the like. It has a first light receiving unit 18 and a second light receiving unit 19.

In the displacement detection device 101, the separation optical system is configured by the polarization beam splitter 113 and the phase plate 125. The first lens 12, the objective lens 14, the second lens 15, the astigmatism generating section 16, the split optical system 17, the first light receiving section 18, and the second light receiving section 19 are examples of the first embodiment. Since it is the same as the displacement detection device 1 according to the above, the description thereof will be omitted.

The polarization beam splitter 113 reflects s-polarized light and transmits p-polarized light. Then, the light L emitted from the light source 11 is converted into p-polarized light before it is incident on the polarizing beam splitter 113. Therefore, the light L incident on the polarizing beam splitter 113 passes through the polarizing beam splitter 113. A phase plate 125 is arranged between the polarizing beam splitter 113 and the objective lens 14.

The phase plate 125 is composed of, for example, a 1/4 wave plate or the like. Therefore, when the passing light is p-polarized light, the phase plate 125 converts it into circularly polarized light that rotates in the first direction with the traveling direction as the central axis. Further, when the passing light is circularly polarized light that rotates in the first direction, it is converted into s-polarized light. Further, when the passing light is s-polarized light, it is converted into circularly polarized light that rotates in a second direction opposite to the first direction with the traveling direction as the central axis. Then, when the passing light is circularly polarized light that rotates in the second direction, it is converted into p-polarized light.

Since the polarization direction of the light L passing through the polarization beam splitter 113 is p-polarized light, it is converted into circularly polarized light that rotates in the first direction with the traveling direction as the central axis by passing through the phase plate 125. .. Further, the polarization directions of the first reflected light L1 reflected by the front surface T1 of the object T to be measured and the second reflected light L2 reflected by the back surface T2 are centered on the traveling direction before passing through the phase plate 125. It is circularly polarized light that rotates in the first direction. Therefore, when the first reflected light L1 and the second reflected light L2 pass through the phase plate 125, the polarization direction thereof is converted into s-polarized light.

Since the polarization direction of the first reflected light L1 and the second reflected light L2 is s-polarized light, the first reflected light L1 and the second reflected light L2 are reflected by the polarization beam splitter 113 and irradiated to the second lens 15.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 101 having such a configuration can also obtain the same effects as the displacement detection device 1 according to the first embodiment described above.

Further, when the object T to be measured does not have polarization characteristics such as birefringence, the displacement detection device 101 according to the second embodiment is more to be measured than the displacement detection device 1 according to the first embodiment. The amount of light L to irradiate the object T can be increased, and signal quality such as noise level can be improved.

3. 3. Example of Third Embodiment Next, the displacement detection device according to the third embodiment will be described with reference to FIGS. 8 to 11.
FIG. 8 is a schematic configuration diagram showing the configuration of the displacement detection device according to the third embodiment. FIG. 9 is a block diagram showing a thickness detection unit of the displacement detection device according to the third embodiment. FIG. 10 is an explanatory diagram showing an example of an irradiation image irradiated on the light receiving surfaces of the first light receiving unit and the second light receiving unit in the displacement detection device according to the third embodiment. FIG. 11 is an explanatory diagram showing the characteristics of the focus signal obtained from the amount of light detected by the first light receiving unit and the second light receiving unit of the displacement detection device according to the third embodiment.

The displacement detection device 201 according to the third embodiment uses the knife edge method instead of the astigmatism generating portion in the displacement detection device 1 according to the first embodiment. Therefore, here, the same reference numerals are given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

The displacement detection device 201 has a head 202 facing the object T to be measured and a thickness detection unit 203 for calculating the thickness. The head 202 includes a light source 211, a first lens 212, a separation optical system 213, an objective lens 214, a second lens 215, a split optical system 217, a first knife edge 226, and a second knife edge 227. It has a first light receiving unit 218 and a second light receiving unit 219. Since the light source 211, the first lens 212, the separation optical system 213, the objective lens 214, the second lens 215, and the split optical system 217 are the same as the displacement detection device 1 according to the first embodiment, the description thereof will be described. Omit.

The first knife edge 226 is arranged between the split optical system 217 and the first light receiving unit 218, and the second knife edge 227 is arranged between the split optical system 217 and the second light receiving unit 219. The first knife edge 226 shields substantially half of the area of the plane orthogonal to the optical axis of the light in which the first reflected light L1 and the second reflected light L2 reflected by the split optical system 217 overlap. Similarly, the second knife edge 227 shields approximately half of the area of the plane in which the first reflected light L1 and the second reflected light L2 transmitted through the split optical system 217 overlap each other and is orthogonal to the optical axis. ..

Further, in the distance h3 between the first knife edge 226 and the split optical system 217, the first reflected light L1 is formed in the vicinity of the first knife edge 226, and the second reflected light L2 is the light receiving surface of the first light receiving portion 218. It is set to the length that diverges in. Further, in the distance h4 between the second knife edge 227 and the split optical system 217, the second reflected light L2 is formed in the vicinity of the second knife edge 227, and the first reflected light L1 is received by the second light receiving portion 219. The length is set to diverge on the surface. The positions where the first knife edge 226 and the second knife edge 227 are arranged are adjusted according to the thickness A1 of the object T to be measured.

As shown in FIG. 9, the thickness detection unit 203 includes a first absolute position calculation unit 221 connected to the first light receiving unit 218 and a second absolute position calculation unit 222 connected to the second light receiving unit 219. , A first absolute position calculation unit 221 and a comparator 223 connected to the second absolute position calculation unit 222.

The first absolute position calculator 221 has a differential amplifier 253 and an absolute position calculator 254. The differential amplifier 253 is connected to the first light receiving element 231 of the first light receiving unit 218 and the second light receiving element 232. The differential amplifier 253 differentially amplifies the signal photoelectrically converted by the first light receiving element 231 and the second light receiving element 232. The differential amplifier 253 is connected to the absolute position calculator 254. Then, the absolute position calculator 254 calculates the absolute position information in the height direction Z on the surface T1 of the object T to be measured based on the signal from the differential amplifier 253.

The second absolute position calculation unit 222 has a differential amplifier 263 and an absolute position calculation unit 264, similarly to the first absolute position calculation unit 221. The differential amplifier 263 is connected to the first light receiving element 241 of the second light receiving unit 219 and the second light receiving element 242. The differential amplifier 263 differentially amplifies the signal photoelectrically converted by the first light receiving element 241 and the second light receiving element 242. The differential amplifier 263 is connected to the absolute position calculator 264. Then, the absolute position calculator 264 calculates the absolute position information in the height direction Z on the back surface T2 of the object T to be measured based on the signal from the differential amplifier 263.

The comparator 223 is connected to the absolute position calculator 254 of the first absolute position calculator 221 and the absolute position calculator 264 of the second absolute position calculator 222. The comparator 223 has the thickness of the object T to be measured from the difference between the absolute position information of the front surface T1 calculated by the first absolute position calculation unit 221 and the absolute position information of the back surface T2 calculated by the second absolute position calculation unit 222. Is calculated, and the calculated thickness is output.

As shown in FIG. 10, the first light receiving elements 231 and 241 and the second light receiving elements 232 and 242 of the first light receiving unit 218 and the second light receiving unit 219 face each other with the optical axis interposed therebetween. An irradiation image P of the first reflected light L1 or the second reflected light L2 is formed on the two light receiving elements 231, 241, 232, and 242 of the first light receiving unit 218 and the second light receiving unit 219, respectively. Specifically, an irradiation image of the first reflected light L1 is formed on the two light receiving elements 231 and 232 of the first light receiving unit 218, and the two light receiving elements 241 and 242 of the second light receiving unit 219 are formed. Is irradiated with the irradiation image of the second reflected light L2.

In the first reflected light L1 and the second reflected light L2, approximately half of the plane orthogonal to the optical axis is shielded by the first knife edge 226 and the second knife edge 227. Therefore, when the absolute position of the front surface T1 or the back surface T2 in the height direction Z changes, the irradiation image P irradiated to the first light receiving unit 218 or the second light receiving unit 219 is the first light receiving element 231 or 241 side. Alternatively, it moves to the second light receiving element 232, 242 side.

Therefore, the first absolute position calculation unit 221 and the second absolute position calculation unit 222 differentially amplify the signals photoelectrically converted by the two light receiving elements 231, 241, 232, and 242 by the differential amplifiers 253 and 263, respectively. As a result, it is possible to obtain a focus signal as shown in FIG. 11, which is similar to the displacement detection device 1 according to the first embodiment.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 201 having such a configuration using the knife edge method can also obtain the same operation and effect as the displacement detection device 1 according to the above-described first embodiment.

4. Example of Fourth Embodiment Next, the displacement detection device according to the fourth embodiment will be described with reference to FIGS. 12 and 13.
FIG. 12 is a schematic configuration diagram showing the configuration of the displacement detection device according to the fourth embodiment. FIG. 13 is an explanatory diagram showing an example of an irradiation image irradiated on the light receiving surfaces of the first light receiving side light guide member and the second light receiving side light guide member in the displacement detection device according to the fourth embodiment.

The displacement detection device 301 according to the fourth embodiment has a head 2 with a light source 11, a first light receiving unit 18, and a second light receiving unit 19 in the displacement detection device 1 according to the first embodiment. It is placed on the outside. Therefore, here, the same reference numerals are given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

As shown in FIG. 12, the displacement detection device 301 includes a light source 11, a head 302, a first light receiving unit 325, a second light receiving unit 326, and a thickness detecting unit 3. The head 302 is arranged with a first lens 12, a separation optical system 13, an objective lens 14, a second lens 15, an astigmatism generating unit 16, and a split optical system 17.

Further, the displacement detection device 301 includes an irradiation side light guide member 304, a first light receiving side light guide member 305, and a second light receiving side light guide member 306. The irradiation side light guide member 304 is made of, for example, an optical fiber. The irradiation side light guide member 304 guides the light L emitted from the light source 11 to the first lens 12 of the head 302.

The first light receiving side light guide member 305 guides the first reflected light L1 reflected by the split optical system 17 to the first light receiving unit 18. Then, the second light receiving side light guide member 306 guides the second reflected light L2 transmitted through the split optical system 17 to the second light receiving unit 19. Further, the first light receiving side light guide member 305 and the first light receiving unit 18 form a first light receiving unit 325, and the second light receiving side light guide member 306 and the second light receiving unit 19 form a second light receiving unit 326. is doing. Therefore, the light receiving surface of the first light receiving side light guide member 305 that receives light becomes the light receiving surface of the first light receiving unit 325. Further, the light receiving surface of the second light receiving side light guide member 306 that receives light becomes the light receiving surface of the second light receiving unit 326.

The distance h1 between the light receiving surface of the first light receiving side light guide member 305 and the split optical system 17 is the light receiving surface of the first light receiving unit 18 and the split optical system 17 in the displacement detection device 1 according to the first embodiment. It is set to be equal to the interval h1. Therefore, the irradiation image P1 of the first reflected light L1 is formed on the light receiving surface of the first light receiving side light guide member 305, and the second reflected light L2 is diverged. Therefore, the first light receiving side light guide member 305 can guide the first reflected light L1 to the first light receiving unit 18.

The distance h2 between the light receiving surface of the second light receiving side light guide member 306 and the split optical system 17 is the light receiving surface of the second light receiving unit 19 and the split optical system 17 in the displacement detection device 1 according to the first embodiment. It is set to be equal to the interval h1. Therefore, the irradiation image P2 of the second reflected light L2 is formed on the light receiving surface of the second light receiving side light guide member 306, and the first reflected light L1 is diverged. Therefore, the second light receiving side light guide member 306 can guide the second reflected light L2 to the second light receiving unit 19.

As shown in FIG. 13, the first light receiving side light guide member 305 and the second light receiving side light guide member 306 are the first optical fiber 321 and the second optical fiber 322, the third optical fiber 323, and the fourth, respectively. It has an optical fiber 324. The first optical fiber 321 and the second optical fiber 322, the third optical fiber 323, and the fourth optical fiber 324 are arranged around the optical axis of light. The first optical fiber 321 and the second optical fiber 322 face each other with the optical axis interposed therebetween, and the third optical fiber 323 and the fourth optical fiber 324 face each other with the optical axis interposed therebetween.

The light emitting end of the first optical fiber 321 faces the first light receiving elements 31 and 41 (see FIGS. 6B and 7B) of the light receiving units 18 and 19. The light emitting end of the second optical fiber 322 faces the second light receiving elements 32 and 42 of the light receiving units 18 and 19, and the light emitting end of the third optical fiber 323 is the third light receiving end of the light receiving units 18 and 19. It faces the elements 33 and 43. The fourth optical fiber 324 faces the fourth light receiving elements 34 and 44 of the light receiving units 18 and 19.

An irradiation image of the first reflected light L1 that is applied to the light receiving surfaces of the first light receiving side light guide member 305 and the second light receiving side light guide member 306 when the absolute positions of the front surface T1 and the back surface T2 in the height direction Z change. The irradiation image P2 of P1 and the second reflected light L2 has an elliptical shape extending toward the first optical fiber 321 and the second optical fiber 322, or an elliptical shape extending toward the third optical fiber 323 and the fourth optical fiber 324. Change.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 301 having such a configuration can also obtain the same effects as the displacement detection device 1 according to the first embodiment described above.

According to the displacement detection device 401 according to the fourth embodiment, the light source 11 as a heat source can be separated from other members. In addition, maintenance of the light source 11, the first light receiving unit 18, and the second light receiving unit 19 becomes possible at a place away from the head 302, and workability is improved. Further, it is possible to prevent the light and the influence on the first light receiving unit 18 and the second light receiving unit 19 due to the strong magnetic field from the outside.

5. Example of Fifth Embodiment Next, the displacement detection device according to the fifth embodiment will be described with reference to FIG.
FIG. 14 is a schematic configuration diagram showing the configuration of the displacement detection device according to the fifth embodiment.

The displacement detection device 401 according to the fifth embodiment is the light source 211 in the displacement detection device 201 according to the third embodiment, similarly to the displacement detection device 301 according to the fourth embodiment. The first light receiving unit 218 and the second light receiving unit 219 are arranged outside the head 202. Therefore, here, the parts common to the displacement detection device 1 according to the first embodiment and the displacement detection device 201 according to the third embodiment are designated by the same reference numerals and duplicated description will be given. Omit.

As shown in FIG. 14, the displacement detection device 401 includes a light source 211, a head 402, a first light receiving unit 425, a second light receiving unit 426, and a thickness detecting unit 203. A first lens 212, a separation optical system 213, an objective lens 214, a second lens 215, a split optical system 217, a first knife edge 226, and a second knife edge 227 are arranged on the head 402. There is.

Further, the displacement detection device 401 includes an irradiation side light guide member 404, a first light receiving side light guide member 405, and a second light receiving side light guide member 406. The irradiation side light guide member 404 is made of, for example, an optical fiber. The irradiation side light guide member 404 guides the light L emitted from the light source 211 to the first lens 212 of the head 402.

The first light receiving side light guide member 405 guides the first reflected light L1 to the first light receiving unit 218, and the second light receiving side light guide member 406 guides the second reflected light L2 to the second light receiving unit 219. Guide light. Further, the first light receiving side light guide member 405 and the first light receiving unit 218 constitute the first light receiving unit 425, and the second light receiving side light guide member 406 and the second light receiving unit 219 form the second light receiving unit 426. is doing.

The first light receiving side light guide member 405 includes a first optical fiber 431, a second optical fiber 432, and a triangular reflection prism 433. The apex of the reflection prism 433 coincides with the optical axis of the first reflected light L1 reflected by the split optical system 217. Further, the two reflecting surfaces arranged with the apex of the reflecting prism 433 sandwiched between them are arranged along the moving direction of the irradiation image that moves when the surface T1 of the object to be measured is displaced in the height direction. There is.

The light receiving surfaces of the first optical fiber 431 and the second optical fiber 432 that receive light face each other with the reflection prism 433 in between. Further, the light emitting end of the first optical fiber 431 faces the first light receiving element 231 (see FIG. 10) of the first light receiving unit 218, and the light emitting end of the second optical fiber 432 is the first. It faces the second light receiving element 232 (see FIG. 10) of the light receiving unit 218.

The second light receiving side light guide member 406 has a first optical fiber 441, a second optical fiber 442, and a triangular reflection prism 443, similarly to the first light receiving side light guide member 405. The apex of the reflection prism 443 coincides with the optical axis of the second reflected light L2 transmitted through the split optical system 217. Further, the two reflecting surfaces arranged with the apex of the reflecting prism 443 sandwiched between them are arranged along the moving direction of the irradiation image that moves when the back surface T2 of the object T to be measured is displaced in the height direction. There is.

The light receiving surfaces of the first optical fiber 441 and the second optical fiber 442 that receive light face each other with the reflection prism 443 in between. Further, the light emitting end of the first optical fiber 441 faces the first light receiving element 241 (see FIG. 10) of the second light receiving unit 219, and the light emitting end of the second optical fiber 442 is the second light receiving end. It faces the second light receiving element 242 (see FIG. 10) of the light receiving unit 219.

Since other configurations are the same as those of the displacement detection device 201 according to the third embodiment, their description will be omitted. The displacement detection device 401 having such a configuration also obtains the same effects as the displacement detection device 201 according to the third embodiment and the displacement detection device 301 according to the fourth embodiment described above. Can be done.

6. Example of Sixth Embodiment Next, the displacement detection device according to the sixth embodiment will be described with reference to FIG.
FIG. 15 is a schematic configuration diagram showing the configuration of the displacement detection device according to the sixth embodiment.

The displacement detection device 501 according to the sixth embodiment uses the head 2 of the displacement detection device 1 according to the first embodiment, and is in a direction orthogonal to the height direction Z, that is, an object to be measured. It is a device that detects the absolute position of the lateral direction X parallel to the front surface and the back surface. Therefore, here, the same reference numerals are given to the parts common to the displacement detection device 1 according to the first embodiment, and duplicate description will be omitted.

As shown in FIG. 15, the displacement detection device 501 includes a head 2, a displacement measurement unit 503, and a scale 505. The head 2 and the scale 505 face each other, and at least one of them is arranged so as to be movable in the lateral direction X. Since the configuration of the head 2 is the same as that of the head 2 of the displacement detection device 1 according to the first embodiment, the description thereof will be omitted here.

The scale 505 is formed in a substantially flat plate shape. The scale 505 has a front surface 505a facing the head 2 and a back surface 505b facing the front surface 505a. The scale 505 is made of a member capable of transmitting the light L emitted from the head 2. Further, the scale 505 reflects the light L emitted from the head 2 on the front surface 505a and the back surface 505b.

The front surface 505a and the back surface 505b are arranged substantially parallel to the lateral direction X orthogonal to the height direction Z, which is a direction facing each other. The thickness A1 of the scale 505 in the height direction Z, that is, the distance between the front surface 505a and the back surface 505b is continuously constantly inclined or gradually changed along the lateral direction X.

The displacement measuring unit 503 includes a first absolute position calculation unit 521, a second absolute position calculation unit 522, a comparator 523, and a displacement converter 524.

The first absolute position calculation unit 521 calculates the absolute position information in the height direction Z on the surface 505a of the scale 505 based on the signal photoelectrically converted by the first light receiving unit 18. The second absolute position calculation unit 522 calculates the absolute position information in the height direction Z on the back surface 505b of the scale 505 based on the signal photoelectrically converted by the second light receiving unit 19. The method of calculating the absolute position information of the front surface 505a and the back surface 505b in the first absolute position calculation unit 521 and the second absolute position calculation unit 522 is the first absolute position calculation unit 21 and the first absolute position calculation unit 21 according to the first embodiment. 2 It is the same as the calculation method of the absolute position information of the front surface T1 and the back surface T2 of the object T to be measured in the absolute position calculation unit 22.

The comparator 523 is based on the difference between the absolute position information of the front surface 505a of the scale 505 calculated by the first absolute position calculation unit 521 and the absolute position information of the back surface 505b of the scale 505 calculated by the second absolute position calculation unit 522. The thickness A2 of the scale 505 is calculated. Then, the comparator 523 is connected to the displacement converter 524, and outputs the calculated thickness A2 information of the scale 505 to the displacement converter 524.

The displacement transducer 524 stores a table in which the thickness A2 information on the scale 505 and the absolute position information on the scale 505 in the lateral direction X are opposed to each other. The displacement transducer 524 refers to the table stored in advance and converts the thickness A2 information of the scale 505 output from the comparator 523 into the absolute position information in the lateral direction X. As a result, according to the displacement detection device 501 according to the sixth embodiment, the absolute position of the scale 505 in the lateral direction X can be detected from the thickness A2 of the scale 505.

For example, a case where the thickness A2 of the scale 505 is 1 mm and the surface 505a is provided with an inclination of 10 μm / mm in the lateral direction X will be described. That is, when the scale 505 is displaced by 1 mm in the lateral direction X, the thickness A2 changes by 10 μm. In this case, by setting the detection range of the focus signal to ± 50 μm, the length of the measurement range in the lateral direction X becomes 10 mm. At this time, the detection resolution in the height direction Z is about 5 nm, which is 1/10000 of the focus signal detection range, and the detection resolution in the lateral direction X is 0.5 μm.

Since other configurations are the same as those of the displacement detection device 1 according to the first embodiment, their description will be omitted. The displacement detection device 501 having such a configuration can also obtain the same effects as the displacement detection device 1 according to the first embodiment described above.

As the head of the displacement detection device 501 according to the sixth embodiment, the heads of the displacement detection devices 101 to 401 according to the second to fourth embodiments may be used.

The present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be made without departing from the gist of the invention described in the claims. In the above-described embodiment, the light emitted from the light source may be supplied by flying not only in a gas but also in a space in a liquid or a vacuum.

Further, in the displacement detection device according to the above-described embodiment, an example of measuring the thickness of the object to be measured from the absolute position information of the front surface and the back surface of the object to be measured has been described, but the present invention is not limited to this. .. The displacement detection device of the present invention may, for example, measure the distance between two surfaces from the absolute position information of any two surfaces facing each other in the object to be measured.

Although words such as "parallel" and "orthogonal" have been used in the present specification, these do not mean only strict "parallel" and "orthogonal", but include "parallel" and "orthogonal". Further, it may be in a "substantially parallel" or "substantially orthogonal" state within a range in which the function can be exhibited.

1 ... displacement detection device, 2 ... head, 3 ... thickness detector, 11 ... light source, 12 ... first lens, 13 ... separation optical system, 14 ... objective lens, 15 ... second lens (condensing lens), 16 ... Non-point aberration generating unit, 17 ... Split optical system, 18 ... First light receiving unit (first light receiving unit), 19 ... Second light receiving unit (second light receiving unit), 21 ... First absolute position calculation unit, 22 ... 2nd absolute position calculation unit, 23 ... Comparer, 31, 32, 33, 34, 41, 42, 43, 44 ... Light receiving element, 226 ... 1st knife edge, 227 ... 2nd knife edge, 304 ... Irradiation side Light guide member, 305 ... 1st light receiving side light guide member, 306 ... 2nd light receiving side light guide member, 325 ... 1st light receiving unit, 326 ... 2nd light receiving unit, 505 ... Scale, 505a ... Surface (first surface) ), 505b ... Back surface (second surface), 524 ... Displacement converter, A1 ... Thickness, f1 ... Focus position, L ... Light, L1 ... First reflected light ,, L2 ... Second reflected light, P1, P2 ... Irradiation image, T ... object to be measured, T1 ... front surface (first surface), T2 ... back surface (second surface), X ... lateral direction, Z ... height direction

Claims (10)

Light source and
An objective lens that collects the light emitted from the light source toward the object to be measured, and
The optical path of the first reflected light reflected by the first surface of the object to be measured and the second reflected light reflected by the second surface facing the first surface of the object to be measured is transmitted from the light source. A separation optical system that separates the emitted light from the optical path,
A condenser lens that collects the first reflected light and the second reflected light separated from the optical path of the light emitted from the light source by the separation optical system.
An astigmatism generating portion that causes astigmatism in the first reflected light and the second reflected light collected by the condensing lens, and
A split optical system that divides the light in which the first reflected light and the second reflected light, in which astigmatism is generated by the astigmatism generating portion, into two.
A first light receiving unit that receives the first reflected light from the light divided into two by the divided optical system, and a first light receiving unit.
A second light receiving unit that receives the second reflected light from the light divided into two by the divided optical system, and a second light receiving unit.
In the height direction in which the first surface and the second surface of the first surface of the object to be measured face each other based on the amount of the first reflected light received by the first light receiving unit. The first absolute position calculation unit that calculates absolute position information,
A second absolute position calculation unit that calculates absolute position information in the height direction of the second surface of the object to be measured based on the amount of the second reflected light received by the second light receiving unit.
The first in the object to be measured is based on the difference between the absolute position information of the first surface calculated by the first absolute position calculation unit and the absolute position information of the second surface calculated by the second absolute position calculation unit. A comparator for calculating the distance between the first surface and the second surface in the height direction is provided.
The first absolute position calculation unit and the second absolute position calculation unit calculate the absolute position information of the first surface and the absolute position information of the second surface in synchronization with each other.
The first reflected light and the second reflected light share the separation optical system, the condensing lens, the astigmatism generating portion, and the dividing optical system, and the same separation optical system, the condensing lens, and the non-pointing optical system. A displacement detection device that passes through the astigmatism generating portion and the divided optical system. The light receiving surface of the first light receiving unit is arranged at a position where an irradiation image of the first reflected light is formed on the light receiving surface of the first light receiving unit and the second reflected light is emitted.
The first aspect of the present invention, wherein the light receiving surface of the second light receiving unit is arranged at a position where an irradiation image of the second reflected light is formed on the light receiving surface of the second light receiving unit and the first reflected light is diverged. Displacement detector. It has a lens holding portion that supports the objective lens so as to be movable in the optical axis direction of the objective lens.
The displacement detection device according to claim 1 or 2, wherein the lens holding portion fixes the objective lens at a predetermined position when measuring. Wherein at least one of the light receiving surface of the light receiving surface and the second light receiving unit of the first light receiving unit 3 from claim 1, which is supported movably along the optical axis direction of the light emitted from the splitting optical system The displacement detection device according to any one of the above items. The astigmatism generating unit claims 1 transparent arranged obliquely a substrate, or a cylindrical lens with respect to the optical path of the first reflected light and the second reflected light is emitted from the condenser lens The displacement detection device according to any one of 4. The displacement detection device according to any one of claims 1 to 5 , wherein the objective lens is provided with an achromatic measure. The first absolute position calculation unit divides the calculated absolute position information of the first surface by the total amount of light received by the first light receiving unit.
The displacement detection device according to any one of claims 1 to 6 , wherein the second absolute position calculation unit divides the calculated absolute position information of the second surface by the total light receiving amount obtained by the second light receiving unit. .. The light transmitted through the first surface is reflected on the second surface, and the light is reflected on the second surface.
The coefficient of the refractive index of the object to be measured is substituted in advance in either one of the second absolute position calculation unit and the comparator.
The comparator according to any one of claims 1 to 7 , wherein the comparator corrects the distance between the first surface and the second surface in the height direction of the object to be measured, which is calculated based on the refractive index. Displacement detector. An irradiation-side light guide member that guides the light emitted from the light source to the objective lens is provided.
The first light receiving unit is
A first light receiving unit having a plurality of light receiving elements and
It has a first light receiving side light guide member that guides the light emitted from the split optical system to the first light receiving portion.
The second light receiving unit is
A second light receiving unit having a plurality of light receiving elements and
The displacement detection device according to any one of claims 1 to 8 , further comprising a second light receiving side light guide member that guides light emitted from the split optical system to the second light receiving portion. The object to be measured is a scale in which the distance between the first surface and the second surface in the height direction changes continuously or stepwise along the lateral direction orthogonal to the height direction.
Further provided with a displacement transducer in which a table in which information on the distance between the first surface and the second surface in the scale in the height direction and absolute position information in the lateral direction are associated with each other is stored.
The displacement converter converts the height distance between the first surface and the second surface calculated by the comparator into the absolute position information in the lateral direction, and the absolute position in the lateral direction of the scale. The displacement detection device according to any one of claims 1 to 9 , which outputs position information.

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