JPH0465614A - Optical surface roughness measuring instrument - Google Patents

Abstract

PURPOSE:To cancel the influence due to disturbance such as vibration and to measure the ruggedness of the surface of a body to be measured with high accuracy by measuring the ruggedness of the surface based on the difference between a displacement quantity measured with reference light and a displacement quantity measured with photometric light. CONSTITUTION:The differential signal (e) between measurement signals Sa and Sb corresponds to a displacement quantity DM, i.e. a displacement quantity (d+d') which is the sum of a displacement quantity d' due to the vibration of the whole body 28 to be measured and a displacement quantity (d) due to the ruggedness of the surface 30 and the differential signal Re between reference signals SRa and SRb corresponds to a displacement quantity DR, i.e. the displacement quantity d' due to the vibration of the whole body 28, so the difference between those differential signals (e) and Re corresponds to the displacement quantity only due to the ruggedness of the surface 30 of the body 28 and the influence due to the disturbance such as the vibration is canceled to measure the ruggedness of the surface 30 with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical surface roughness measuring device, and in detail:
The present invention relates to a device that measures the unevenness of a surface by utilizing the fact that the convergence/divergence state of reflected light changes as the position of light reflection changes in accordance with the unevenness of the surface.

Conventional technology A type of optical surface roughness measuring device that measures the surface roughness and minute irregularities of the object to be measured. By concentrating the measurement light on a minute area of the surface while the surface is approximately located, and detecting changes in the convergence/divergence state of the measurement light reflected on the surface, the position of reflection of the measurement light due to the unevenness of the surface can be determined. There is a type that measures the amount of displacement. As one means for detecting a change in the convergence/divergence state, the Knifezi method is known, in which a shift in the light focusing position is detected using a Knifezi and a two-split optical sensor.

To explain this knife method in detail with reference to FIG. 2, if point B is at the focal position of the objective lens IO, the light ray from point B becomes a parallel ray after passing through the objective lens 10 and passes through the knife 12. After the lower half of the luminous flux is blocked by the condenser lens 22, it is irradiated onto the two-split optical sensor 14. Since the two-split optical sensor 14 is located at the focal point of the condensing lens 22, the light emitted from point B is split into two parts.
The light is focused on the center position on the split light sensor 14.

This light is received by a pair of light receiving parts 16a and 16b which respectively receive light on the upper side and the lower side of the optical axis as a boundary in the figure. When the light is focused at the center position, the amount of light received by each light receiving section is equal to each other, and the differential signal of the light receiving sections 16a and 16b becomes 0.

However, when the emission point moves toward point A, the objective lens 10
Since the light beam that exits becomes a diverging light, the position (beam waist) at which the upper half of the light flux that is not blocked by the knife beam 12 is focused by the condenser lens 22 is farther than the position of the two-split optical sensor 14, and the light beam is mainly divided into two parts. The upper part of the optical sensor 14 is now illuminated. Therefore, the output of the upper light receiving section 16a becomes larger than the output of the lower light receiving section 16b, and the differential signal becomes negative. Conversely, when the emission point moves toward the 0 point side, the light beam exiting the objective lens 10 becomes a convergent light, so that the light beam is focused by the condenser lens 22 in front of the two-split optical sensor 14, and is mainly divided into two. The lower part of the optical sensor 14 is now illuminated. Therefore, the output of the lower light receiving section 16b becomes larger than the output of the upper light receiving section 16a, and the differential signal becomes positive. Therefore, the two-split optical sensor 14
The moving state of the emission point can be detected based on the positive and negative states of the differential signals.

The Naifetsu method is a method of detecting the emission position of light from changes in the convergence/divergence state of the light, and Figure 3 is a schematic diagram showing an example of a device that uses the Naifetsu method to measure surface irregularities. It is. In FIG. 3, a linearly polarized laser beam emitted from a laser oscillator 18 is expanded in beam diameter by a beam expander 20 arranged on the optical axis to become a circular parallel beam, and then sent to a polarizing beam splitter 24. It is made incident. The attitude of the laser oscillator 18 is set so that the plane of polarization of the laser beam (the plane of vibration of the electric hector) is perpendicular to the plane of the paper, and the polarizing beam splitter 24 is arranged so that the plane of incidence is parallel to the plane of the paper.
The laser beam is reflected downward. After passing through the X wavelength plate 26, the reflected laser light is irradiated onto the surface 30 of the object to be measured 28 by the objective lens lO.

The object to be measured 28 has a surface 30 on the optical axis of the laser beam reflected by the polarizing beam splitter 24, which is approximately the same as the beam waist (in this case, the focal point) of the laser beam focused by the objective lens 10. It is placed on a moving table 34 which is moved in a plane perpendicular to the optical axis of the laser beam by drive devices 3 and 2 4'. Therefore, the laser beam is irradiated onto a minute area of the surface 30, and by moving the object to be measured 28 together with the moving table 34 in a direction perpendicular to the optical axis, the reflection position of the laser beam on the surface 30 is It is displaced in the optical axis direction in accordance with the unevenness of the surface 30. Laser light corresponds to measurement light.

The laser beam reflected by the surface 30 passes through the objective lens 10 and the wavelength plate 26 again, so that the direction of the plane of polarization is rotated by 90 degrees compared to the forward path, and the laser beam is transmitted through the polarizing beam splitter 24. Also Naifetsuji 12
The right half of the light beam is blocked by this. The left half of the laser beam passes through the condenser lens 22 and is irradiated onto the two-split optical sensor 14 located at the focal point of the condenser lens 22. The light receiving section 16a of the two-split optical sensor 14,
The amount of light received by 16b is increased or decreased according to the principle shown in the second part, as the reflection position of the laser beam changes due to the unevenness of the surface 30, so that the output signals Sa and Sb corresponding to the amount of light received are The supplied measuring circuit 36 determines the difference between these signals Sa and Sb, and determines the unevenness of the surface 30 from the positive and negative values of the differential signal using, for example, a data map.

Problems to be Solved by the Invention However, in such conventional measurement methods, if the object to be measured is displaced in the optical axis direction of the measurement light due to vibration or other disturbances when the treasure to be measured is moved relative to the object, the Since the surface roughness is measured including the amount of displacement, there is a problem in that sufficient measurement accuracy cannot always be obtained.

The present invention has been made against the background of the above circumstances, and its purpose is to improve measurement accuracy by eliminating the influence of vibrations of the object to be measured.

Means for Solving the Problems In order to achieve the object, the gist of the present invention is to provide a state in which the beam waist is approximately located on the surface of the object to be measured that is relatively moved in a direction intersecting the optical axis. By focusing the measurement light on a minute area of the surface and detecting changes in the convergence/divergence state of the measurement light reflected from the surface, the amount of displacement of the reflection position of the measurement light due to the unevenness of the surface is measured. This is an optical surface roughness measurement device that includes (a) a light source device that emits light containing two types of polarized components whose optical axes are the same and whose polarization planes are orthogonal to each other; and (b) the two types of The polarized light components are each independently focused, and one of the two types of polarized light components is used as measurement light to irradiate a minute range of the surface of the object to be measured so that the beam waist substantially coincides with the surface of the object to be measured, (C) an objective lens that uses the other of the two types of polarized light components as reference light to irradiate a relatively wide range of the surface of the object to be measured; and (C) the measurement light that is reflected on the surface and passed through the objective lens. and a polarizing beam splitter that separates the reference light; (d) blocking half of the measurement light separated by the polarizing beam splitter with a straight line orthogonal to the optical axis as the boundary, and condensing the remaining half; As the convergence/divergence state of the measurement light is changed according to the displacement of the reflection position of the measurement light on the surface, one side and the other side with the plane including the optical axis and the straight line as the boundary are changed. (e) a measurement optical element that reciprocally increases or decreases the amount of measurement light on each side; and (e) disposed across both sides of the boundary where the amount of measurement light is increased or decreased by the measurement optical element;゛A measurement optical sensor that detects the light intensity of the measurement light on the one side and the other side, respectively; By blocking half of the light and concentrating the other half,
As the convergence/divergence state of the reference light is changed according to the displacement of the reflection position of the reference light on the surface, on one side and the other side bounded by a plane containing the optical axis and a straight line. a reference optical element that reciprocally increases or decreases the light intensity of the reference light; Ch) a reference optical sensor that detects the light intensity of the reference light on one side and the other side, respectively; and Ch) a differential measurement signal output from the measurement optical sensor, and a and measuring means for measuring the unevenness of the surface based on the difference between the differential signals.

In the above-mentioned optical surface roughness measuring device, light containing two types of polarized light components having the same optical axis and mutually orthogonal polarization planes is emitted from the light source device, and one of the two types of polarized light components is detected by the objective lens. is focused as measurement light on a small area on the surface of the object to be measured, and the other of the two types of polarized light components is focused as reference light on a relatively wide area on the surface of the object to be measured. The measurement light and reference light reflected by the surface are passed through the objective lens, separated by a polarizing beam splitter, and made incident on a measurement optical element and a reference optical element, respectively.

When the measurement light enters the measurement optical element, half of it is blocked and the other half is focused, and the convergence/divergence state changes according to the displacement of the reflection position on the surface of the object to be measured. , the amount of light is reciprocally increased or decreased on one side and the other side of the plane that includes the optical axis and the boundary line of the above-mentioned light shielding, and the amount of light on both sides is increased or decreased by the measuring optical sensor, respectively. Detected. Furthermore, when the reference light enters the reference optical element, half of it is blocked and the other half is focused, the state of convergence and divergence changes depending on the displacement of the reflection position on the surface of the object to be measured. Accordingly, the amount of light is reciprocally increased or decreased on one side and the other side of the plane containing the optical axis and the boundary line of the light shielding, and the amount of light on both sides is increased or decreased by the reference optical sensor. are detected respectively. Then, the measurement means calculates the difference between the signals output from the measurement optical sensor and the reference optical sensor, and the unevenness of the surface of the object to be measured is measured from the difference between these differential signals.

At this time, the difference in the reference signals output from the reference optical sensor corresponds to the displacement of the part irradiated with the reference light, l, but the reference light irradiates a relatively wide range of the surface of the object to be measured. Since the influence of surface irregularities is averaged by this, the amount of displacement DR corresponds to the amount of displacement d'' of the entire measured object due to vibration etc. Also, the measurement signal output from the measurement optical sensor The differential corresponds to the displacement of the part irradiated with the measurement light, but since the measurement light is irradiated to a minute range on the surface of the object to be measured, the displacement DM is equivalent to the displacement of the part irradiated with the measurement light. corresponds to the displacement amount (d+d') which is the sum of the displacement amount d'' of
) and the displacement amount D0 (-d+d') corresponds to the displacement amount d due only to the unevenness of the surface of the object to be measured, and the influence of external disturbances such as vibrations is canceled out, and the surface unevenness can be measured with high accuracy. Ru.

In addition, the above displacement scale, 1. D does not necessarily need to be determined as a length dimension; it is sufficient that the surface unevenness can be finally determined as a length dimension from the difference in the differential signal, and the difference between the measurement beam and the reference beam can be determined as a length dimension. It is also possible to move the objective lens and the object to be measured relative to each other in the optical axis direction so that one of the dynamic signals becomes zero, and to directly determine the surface unevenness from the other differential signal.

Effects of the Invention As described above, according to the optical surface roughness measuring device of the present invention, in addition to surface roughness measurement using the measurement light, the surface roughness of the object to be measured is measured using the reference light irradiated over a relatively wide range of the surface of the object to be measured. The amount of displacement of the entire object surface is determined, and the unevenness of the surface is measured based on the difference between the amount of displacement measured by this reference light and the amount of displacement determined by the measurement light, thereby eliminating the influence of disturbances such as vibration. are canceled out, and the unevenness on the surface of the object to be measured can be measured with high accuracy.

Further, according to the present invention, the amount of light is detected on both sides of the boundary where the amount of light is reciprocally increased or decreased depending on the displacement of the reflection position on the surface of the object to be measured, and the difference between the two is taken. Therefore, there is an advantage that noise caused by output fluctuations of the light source device, etc. can be removed.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings. In the following embodiments, parts common to those of the conventional example shown in FIG. 3 are given the same reference numerals and detailed explanations will be omitted.

In FIG. 1, the attitude of the laser oscillator 18 is set so that the plane of polarization of the laser beam is inclined at 45 degrees with respect to the plane of the drawing, and the laser beam emitted from the laser oscillator 18 is converted into a beam by a beam expander 20. After the diameter is expanded and the beam is made into a circular parallel beam, the non-polarizing beam splitter 4
0 and is reflected downward by the beam, and is incident on the bifocal lens 42 . The bifocal lens 42 includes optical glass and a birefringent material, and has a characteristic that the refractive index varies depending on the direction of the polarization plane of the incident light beam.

Specifically, P of the laser light whose polarization plane is parallel to the plane of the paper
Regarding the polarized laser beam LP, the object to be measured 28
The beam waist is located approximately on the surface 30 and is focused so as to irradiate a minute area on the surface 30. On the other hand, for the laser beam L8 of the Sa light component whose polarization plane is perpendicular to the plane of the paper, the beam waist is located on the surface 30. The light is focused below the surface 30 so that a relatively wide range of the surface 30 is irradiated.

In this embodiment, the laser oscillator 18° beam expander 20. A light source device 44 is constituted by the non-polarizing beam splitter 40, and the bifocal lens 42 corresponds to an objective lens. Also, laser light, L
', respectively, are measurement lights.

Corresponds to the reference light.

Since the laser beam LP is irradiated onto a minute range of the surface 30, the object to be measured 28 along with the moving table 34 is aligned with the optical axis j.
By moving the object 28 in the direction perpendicular to the surface 30, the reflection position is displaced in the direction of the optical axis j according to the unevenness of the surface 30. Also, the reflection position is displaced in the direction of the optical axis j. On the other hand, since the laser beam is irradiated over a relatively wide range of the surface 30, its reflection position is displaced as the object to be measured 28 moves up and down.
The influence of the unevenness of 0 is averaged out and has almost no effect on the displacement of the reflection position. In other words, the displacement DH of the reflection position of the laser beam LP on the surface 30 is the sum of the displacement d due to the unevenness of the surface 30 and the displacement d" due to vibration of the entire object to be measured 28 (d+d"). Therefore, the laser l
.

The amount of displacement Dm of the reflection position on the surface 30 becomes the amount of displacement d' of the entire object to be measured 28 due to vibration or the like.

Laser beams LP and RI reflected by surface 30.

is passed through the bifocal lens 42 in reverse and transmitted through the non-polarizing beam splitter 40, and is then transmitted through the polarizing beam splitter 4.
6. The plane of incidence of the polarizing beam splitter 46 is parallel to the plane of the paper, and the plane of polarization is parallel to the plane of the paper.
is transmitted through the polarizing beam splitter 46, while laser light whose plane of polarization is perpendicular to the paper plane is reflected to the right by the polarizing beam splitter 46. The laser beam LF transmitted through the polarizing beam splitter 46 is blocked by the knife 12 on the right half of the optical axis j in FIG. The light is made incident on the split light sensor 14. Note that the distance between the condenser lens 22 and the two-split optical sensor 14 is made to match the focal length of the condenser lens 22.

The two-split optical sensor 14 is arranged on one side bounded by a plane including a straight line that is the cutting line of the knife 12 and the optical axis of the laser beam, and on the other side, that is, on the left side bounded by the optical axis j in FIG. It is provided with a pair of light receiving sections 16a and 16b that are disposed straddling both right sides and detect the amount of laser light on both sides, respectively.

The laser beam before entering the condensing lens 22 is parallel light, and the condensing lens 22 converts the laser beam into parallel light.

When the light is focused on the center position of the two-split optical sensor 14, the detection outputs of the amounts of light received by the light receiving sections 16a and 16b are adjusted to be approximately equal. The knife 12 and the condensing lens 22 correspond to a measuring optical element, and the two-split optical sensor 14 corresponds to a measuring optical sensor.

Here, the laser light reflected by the convexly displaced micro-range portion of the surface 30 becomes a divergent state after passing through the bifocal lens 42, and the condensing position where the light is condensed by the condensing lens 22 is 2. Since the position is farther than the split light sensor 14, the irradiation is mainly on the left side of the optical axis j, and the detection output Sa of the light receiving section 16a becomes large, while the detection output Sa of the light receiving section 16b increases.
The detection output sb of becomes small. The difference in the amount of light received at this time corresponds to the amount of upward displacement due to the convex shape on the surface 30. On the contrary, the laser beam LP reflected by the concavely displaced minute range of the surface 30 becomes convergent after passing through the bifocal lens 42, and the condensing position where the condensing lens 22 condenses the light is divided into two. Since the light is closer to the position of the optical sensor 14, it is mainly irradiated to the right side of the optical axis j, and the detection output Sa of the light receiving section 16a becomes small, while the detection output sb of the light receiving section 16b becomes large. The difference in the amount of light received at this time corresponds to the amount of downward displacement due to the concave shape on the surface 30.

On the other hand, the lower half of the laser beam reflected by the polarizing beam splitter 46 on the optical axis in FIG. 1 is blocked by a knife 48 similar to the knife 1.2, so that the upper half of the beam is optical lens 22
The light is focused by a condensing lens 58 similar to the above, and is made incident on the two-split optical sensor 50. Note that the condenser lenses 58 and 2
The distance to the split light sensor 50 is made to match the focal length of the condensing lens 58.

The two-split optical sensor 50 is arranged on one side and the other side bounded by a plane including a straight line that is the enshiline of the knife 48 and the optical axis of the laser beam, that is, the upper and lower sides bounded by the optical axis k in FIG. A pair of light receiving sections 52a and 52b are disposed across both sides, and each detects the amount of laser light LS on both sides.

Since the beam waist of this laser beam LS due to the bifocal lens 42 is located below the surface 30, the light reflected from the surface 30 and passing through the bifocal lens 42 in the opposite direction becomes diverging light. Since there is a difference in the amount of light received above and below the optical axis, the light receiving sections 52a and 52
A bias corresponding to this difference in light amount is applied in advance to b, and is set so that the difference in the detection outputs thereof becomes zero when the beam waist of the laser beam is approximately aligned with the surface 3o. ing. The above Naifetsuji 4
8 and the condenser lens 58 correspond to reference optical elements, and 2
The divided optical sensor 50 corresponds to a reference optical sensor.

Here, when the surface 30 is displaced in the overall Q direction, the laser light reflected in a relatively wide range of the surface 30,
The divergence state is expanded in accordance with the above displacement, and the condensing position (beam waist) where the condensed light is condensed by the condensing lens 58 becomes farther than before, so the irradiation amount on the upper side of the optical axis and the lower The difference between the radiation dose on the side becomes larger than before. At this time, the increase in the difference in the amount of light received by the light receiving sections 52a and 52b of the two-split optical sensor 50 corresponds to the amount of upward displacement of the entire surface 30. Conversely, when the surface 30 is entirely displaced downward, the divergence state of the laser light reflected from a relatively wide range of the surface 30 is reduced in accordance with the displacement,
Since the condensing position where the light is condensed by the condenser lens 58 is closer than before, the difference between the irradiation amount above and below the optical axis becomes smaller than before. At this time, the decrease in the difference in the amount of light received by the light receiving sections 52a and 52b corresponds to the amount of downward displacement of the entire surface 30.

The light receiving portions 16a, 16 of the two-split optical sensor 14
Measurement signals Sa respectively output from b.

sb, and the light receiving part 52a of the two-split optical sensor 50,
Reference signals SRa and SRb respectively output from 52b
is supplied to the measurement circuit 54. The measurement circuit 54 is configured with a microcomputer, for example, and performs signal processing according to a predetermined program to calculate the difference between the measurement signals Sa and Sb and also generates a reference signal SRa.
, take the differential of SRb and 1. From the difference between the differential signals e and Re, the unevenness of the surface 30 is determined using a data map or an arithmetic expression stored in advance. This data map and calculation formula are based on the reflection positions of the laser beams LP and LS and the differential signals qe and Re.
It is determined by determining the relationship between This measuring circuit 54 corresponds to measuring means.

Here, the differential signal e between the measurement signals Sa and sb is the displacement amount DH, that is, the displacement amount ( d+d''), and the reference signals SRa and SRb
Since the differential signal Re between the two corresponds to the displacement d' due to the vibration of the displacement measure l, that is, the entire object to be measured 28, the difference between the differential signals e and Re corresponds to the displacement amount d' of the object to be measured 28. Corresponding to the amount of displacement d due only to the unevenness of the surface 30, the influence of external disturbances such as vibrations is canceled out, and the unevenness of the surface 30 can be measured with high accuracy.

In addition, in the measuring device of this embodiment, the two-split optical sensor 14.5
0 is used and the laser beam LP reflected by the surface 30,
' When half of the luminous flux of Ls is blocked by the knife lens 12.48 and condensed by the condensing lens 22.58, the amount of light is reciprocally increased or decreased as the reflection position on the surface 30 changes2. Laser light at position, L.

Since the amount of light received is detected and the difference between them is taken, there is an advantage that noise caused by fluctuations in the output of the light source device 44, etc. can be removed.

Although one embodiment of the present invention has been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the embodiment described above, each of the laser beams LP and LX is received by one two-split optical sensor 14, 50, but each of these laser beams, ``L'', is divided into two by a beam splitter. By receiving light using two two-split optical sensors, it is also possible to eliminate the effects of diffracted light and the inclination of the object to be measured 28.

Further, in the embodiment described above, the unevenness is measured from the difference between the differential signals e and Re, but for example, the bifocal lens 42 and the object to be measured 28 are driven to move relatively closer to each other in the vertical direction. A device is provided, and the driving device is feedback-controlled so that one of the differential signals e and Re becomes zero, and the surface 3 is controlled only from the other differential signal Re or e.
It is also possible to determine the unevenness of 0.

Also, the condenser lens 2 is adjusted so that the change in the differential signal e becomes zero.
2 and the 2-split photosensor 14 relative to each other in the direction of the optical axis j, and the condensing lens 58 and the 2-segment photosensor 50 to be moved relatively in the direction of the optical axis so that the change in the differential signal Re becomes zero. It is also possible to measure the unevenness of the surface 30 based on the difference in the amount of movement thereof.

Further, in the embodiment described above, the laser beam is always incident on the condenser lens 58 in a diverging state, and the distance between the condenser lens 58 and the two-split optical sensor 5o is
However, in a state where the beam waist of the laser beam substantially coincides with the surface 30, the focal length (beam waist) of the laser beam condensed by the condenser lens 58 and In order to dispose the two-split optical sensor 50 at substantially coincident positions, or to make the laser beam before entering the condensing lens 58 into parallel light, the polarization beam splitter 46 and the condensing lens S8 can be Another condensing lens may be arranged between them, and in these cases, the light receiving parts 52a and 52b of the two-split optical sensor 50
There is no need to apply a predetermined bias to the .

Further, in the embodiment described above, the laser beam that exits the beam expander 2° and becomes a parallel beam with a circular cross section is made incident on the bifocal lens 42, but the laser beam is in the form of convergent light or diverging light. The bifocal lens 42 illuminates the laser beam with
It is also possible to make the light incident on . In that case, surface 3
Another lens may be provided between the polarizing beam splitter 46 and the condenser lens 22.58 so that the laser light reflected by the condenser lens 22. For example, a two-split optical sensor 14.50 may be placed in the area.

Further, although the bifocal lens 42 is used as the objective lens in the above embodiment, a combination of a plurality of lenses that perform a refractive action depending on the direction of the plane of polarization can also be used.

In addition, by attaching multiple bifocal lenses with different focal lengths to a rotary revolver, etc., and changing the measurement magnification by replacing the bifocal lenses, it is possible to It is also possible to insert another objective lens and use a combination thereof to form large and small spots on the surface 30, or to insert an optical isolator between the laser oscillator 18 and the non-polarizing beam splitter 40.

Further, in the embodiment, the knife 12 and the condenser lens 22 are used as the measuring optical element and the reference optical element.
, a knife 48, and a condenser lens 58 are used, but other optical components such as a concave mirror can also be used to configure the measuring optical element and the reference optical element.

Although other examples are not provided, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating the configuration of an optical surface roughness measuring device that is an embodiment of the present invention. FIG. 2 is a diagram illustrating the principle of detecting changes in the convergence/divergence state of light using a knife and a condenser lens. FIG. 3 is a schematic diagram illustrating an example of a conventional optical surface roughness measuring device using a knife and a condensing lens. 14: 2-split optical sensor (measurement optical sensor) 28: Object to be measured 30: Surface 42: Bifocal lens (objective lens) 44: Light source device 46: Polarizing beam splitter l [1 Figure 50: 2-split optical sensor ( Reference optical sensor) 54: Measuring circuit (measuring means)

Claims (1)

[Claims] The beam waist is approximately located on the surface of the object to be measured, which is relatively moved in a direction intersecting the optical axis, and the measurement light is focused on a minute range of the surface. An optical surface roughness measurement device that measures the amount of displacement of the reflection position of the measurement light due to the unevenness of the surface by detecting a change in the convergence/divergence state of the reflected measurement light, the optical axis a light source device that emits light containing two types of polarized light components whose polarization planes are the same and whose planes of polarization are orthogonal to each other; and a light source device that emits light containing two types of polarized light components whose planes of polarization are the same and whose planes of polarization are orthogonal to each other; , irradiates a minute range of the surface of the object to be measured so that its beam waist substantially coincides with the surface of the object to be measured, and uses the other of the two types of polarized light components as a reference beam to irradiate a relatively wide area of the surface of the object to be measured. a polarizing beam splitter that separates the measurement light and reference light that have been reflected by the surface and passed through the objective lens; By blocking half of the light and condensing the remaining half with a straight line orthogonal to the axis as the boundary, the convergence/divergence state of the measurement light can be changed in accordance with the displacement of the reflection position of the measurement light on the surface. Accordingly, a measurement optical element that reciprocally increases or decreases the amount of the measurement light on one side and the other side of the plane including the optical axis and the straight line; a measurement optical sensor disposed across both sides of the boundary where the amount of measurement light is increased or decreased, and detects the amount of measurement light on one side and the other side, respectively; and the polarization beam splitter. By blocking half of the separated reference light along a straight line orthogonal to the optical axis and condensing the other half, the reference light is adjusted according to the displacement of the reflection position of the reference light on the surface. reference optics that reciprocally increases or decreases the light intensity of the reference light on one side and the other side bounded by a plane including the optical axis and the straight line as the convergence/divergence state of the reference light is changed; a reference element, which is disposed straddling both sides of the boundary where the light intensity of the reference light is increased or decreased by the reference optical element, and detects the light intensity of the reference light on the one side and the other side, respectively. Calculate the difference between the measurement signals output from the measurement optical sensor and the measurement optical sensor, and also calculate the difference between the reference signal output from the reference optical sensor, and based on the difference between these differential signals. an optical surface roughness measuring device, comprising a measuring means for measuring the unevenness of the surface.