JPH0465615A - 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 according to 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, etc., of a 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. a displacement quantity d' due to the vibration, etc., of the body 28, so the difference between those differential signals (e) and Re corresponds to the displacement quantity (d) only due to the ruggedness of the surface 30 of the body 28 and the influence of the vibration, etc., is canceled to measured 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 Foucault method is known, which detects a shift in a light focusing position using a light wave splitting prism and a two-split optical sensor.

To explain the Foucault method in detail with reference to FIG. 2, if point B is at the focal point of the objective lens 10, the ray from point B becomes a parallel ray after passing through the objective lens 10, After the light is converged by 22, the light is refracted in opposite directions using the ridgeline of the apex perpendicular to the optical axis as a boundary by the triangular prism-shaped splitting prism I2 arranged so that the apex is located on the optical axis. The light beam is divided into a pair of light beams, L2, which intersect with each other. One beam of light,
is focused on the center of the two-split optical sensor 14 located upwardly away from the optical axis in the figure, and the other light beam L
2 is focused on the center of the two-split optical sensor 16 located at a position spaced downward from the optical axis. At this time, the differential signals of the respective outputs from the light receiving sections 15a, 15b and the light receiving sections 17a, 17b, which are arranged in pairs above and below in the figure with the center of each of the two-split optical sensors 14 and 16 as the border, are zero. Become.

However, when the emission point moves toward point A, the objective lens 10
Since the light rays exiting from the splitting prism 12 become divergent lights, the convergence position (beam waist) of the pair of light beams, L, refracted and split by the splitting prism 12 is smaller than when the exit point is the point B. Each becomes far away.

Therefore, the pair of luminous fluxes L+ and Lz are mainly transmitted to the inner part of the pair of two-split optical sensors 14.16, that is, the light receiving section 15a.
, 17a, and at this time the light receiving section 1
The output differential signals of 5a, 15b, 17a and 17b are negative. Conversely, when the exit point moves toward the 0 point side, objective lens 1
Since the light beam that exits 0 becomes convergent light, the condensing positions of the pair of light beams, . Therefore, the pair of light beams L1. L2 mainly consists of a pair of two-split optical sensors 14.1
6, that is, the light receiving parts 15b and 17b, and at this time the light receiving parts 15a, 15b, 1
The output differential signals of 7a and 17b are positive. therefore,
The moving state of the emission point can be detected based on the positive and negative values of this differential signal.

The Foucault method is a method of detecting the light emitting position from changes in the convergence/divergence state of light, and Figure 3 is a schematic diagram showing an example of a device that uses the Foucault method to measure surface irregularities. It is. In FIG. 3, the linearly polarized laser beam emitted from the laser oscillator 18 is expanded in beam diameter by a beam expander 20 placed on the optical axis to become a circular parallel beam, and then sent to a polarized beam splinter. 2
4. 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 vector) is perpendicular to the plane of the paper, and the polarization 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 wavelength plate 26, the reflected laser light is irradiated onto the surface 30 of the object to be measured 28 by the objective lens 10.

The object to be measured 28 is located on the optical axis of the laser beam reflected by the polarizing beam splitter 24 at a position where the surface 30 substantially coincides with the beam waist of the laser beam focused by the objective lens 10. , is placed on a moving table 34 that is moved by a drive device 32 in a plane perpendicular to the optical axis of the laser beam.

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 wave plate 26 again, so that the direction of the plane of polarization is rotated by 90 degrees compared to the outward path, and the laser beam is transmitted through the polarizing beam splitter 24. After the light is converged by the condenser lens 22, it is refracted by the splitting prism 12 and split into a pair of light beams L+ and Lx. and,
The pair of light beams, L, are received by the light receiving sections 15a, 15b and the light receiving sections 17a, 17b of the two-split photosensors 14 and 16, respectively, which are arranged apart from the optical axis. The amount of light received by the light receiving sections 15a, 15b and the light receiving sections 17a, 17b is increased or decreased according to the principle shown in FIG. In the measurement circuit 36 to which the output signals Sa and Sb corresponding to the amount of received light are supplied, the difference between those signals Sa and SbO is determined,
From the positive and negative values of the differential signal, the unevenness of the surface 30 is determined using, for example, a data map.

Problems to be Solved by the Invention However, in such conventional measurement methods, when the measured object is displaced in the optical axis direction of the measurement light due to vibration or other disturbance when the measured object is moved relative to the measured object, the displacement Since the surface roughness is measured including the amount, there is a problem that sufficient measurement accuracy cannot necessarily 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 such that the beam waist substantially coincides with the surface of the object to be measured, and (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; (C) the measurement light that is reflected on the surface and passed through the objective lens; (d) a polarizing beam splitter that separates the reference beam; (d) refracting at least half of the measuring beam separated by the polarizing beam splitter along a straight line perpendicular to the optical axis; By condensing the light at a position distant from the optical axis on a plane perpendicular to (e) a measuring optical element that moves the condensing position of the measured measuring light back and forth in its traveling direction; (a) a measurement optical sensor that detects the amount of measurement light that reciprocally increases or decreases in response to movement of the focusing position of the measurement light; Displacement of the reflection position of the reference light on the surface by refracting at least half of the line bordering the line and focusing the light at a position away from the optical axis on a plane that includes the optical axis and is perpendicular to the straight line. a reference optical element that moves the condensing position of the refracted reference light back and forth in its traveling direction as the convergence/divergence state of the reference light is changed according to the reference light; reference lights that are disposed on both sides of the reference light refracted by the reference optical element in the traveling direction and detect the amount of the reference light that reciprocally increases or decreases in accordance with the movement of the focal point of the reference light; and (h) taking the difference between the measurement signals output from the measurement optical sensor, and also taking the difference between the reference signals output from the reference optical sensor, and calculating the difference between these differential signals. and measuring means for measuring the unevenness of the surface based on the surface roughness.

Function In such an optical surface roughness measuring device, light containing two types of polarized light components with the same optical axis and mutually orthogonal polarization planes is emitted from the light source device, and the two types of polarized light components are separated by the objective lens. One of the two types of polarized light components is focused as a 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 a 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 separated by a polarizing beam splitter after passing through the objective lens, and are made to enter the measurement optical element and the reference optical element, respectively.

The measurement light, which is incident on the measurement optical element and at least half of it is refracted and focused at a position away from the optical axis, has its convergence/divergence state changed according to the displacement of the reflection position on the surface of the object to be measured. As the light condensing position moves forward and backward in the traveling direction, the light intensity of the measurement light on both sides of the traveling direction, which increases and decreases reciprocally in accordance with the movement of the light condensing position, is measured by the measuring optical sensor. Detected. In addition, for the reference target, which is incident on the reference optical element, at least half of which is refracted and focused at a position distant from the optical axis, the convergence/divergence state changes depending on the displacement of the reflection position on the surface of the measured object. As the light is moved, the light focusing position is moved back and forth in the direction of travel,
The amounts of reference light on both sides of the traveling direction, which reciprocally increase and decrease in accordance with the movement of the light condensing position, are respectively detected by the reference optical sensors. 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 amount of displacement Do+ of the part irradiated with the reference light, but the reference light is irradiated onto a relatively wide range of the surface of the object to be measured. As a result, the influence of surface irregularities is averaged out, so that the amount of displacement Dz+ corresponds to the amount of displacement d° of the entire object to be measured due to vibration or the like. In addition, the difference in the total of 11 J signals output from the measurement optical sensor corresponds to the displacement DM of the part irradiated with the measurement light, but the measurement light is irradiated onto a minute range on the surface of the object to be measured. Therefore, this displacement amount DH corresponds to the displacement amount (d - d'') that is the sum of the displacement amount d'' of all nine objects to be measured and the displacement amount d due to surface irregularities.

Therefore, the difference between those differential signals, that is, the amount of displacement D
The difference between I+ (-d") and displacement measurement (=d+(1") corresponds to the amount of displacement 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 difference between Irregularities can be measured with high accuracy.

Note that the displacement amounts DR and DM do not necessarily need to be determined as length dimensions, and it is sufficient that the surface irregularities can be finally determined as length dimensions from the difference in differential signals, for example, due to measurement light and reference target. 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 differential signals becomes zero, and then 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 measurement light, the surface roughness of the object to be measured is measured using a reference target irradiated over a relatively wide range of the surface of the object to be measured. The amount of displacement of the entire surface of the object is determined, and the unevenness of the surface is measured based on the difference between the amount of displacement measured by this reference and the amount of displacement determined by the measurement light, thereby eliminating the influence of external 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 traveling direction of the refracted light, in which 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 detected. This has the advantage that noise caused by fluctuations in the output 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 paper, and the laser beam emitted from the laser oscillator 18 is transmitted by the beam expander 20. After the beam diameter is expanded and made into circular parallel light, 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 approximately located on the surface 3.0 of the surface 3.0.
On the other hand, for the S-polarized laser beam whose polarization plane is perpendicular to the plane of the paper, the beam waist is below the surface 30 and is focused on a relatively wide area of the surface 30. It is designed to condense light so that it is irradiated.

In this embodiment, the laser oscillator 18° beam expander 20. A light source device 44 is constituted by a non-polarized beam splitter 40, and a bifocal lens 42 corresponds to an objective lens. In addition, laser beams LP, L
S corresponds to measurement light and reference light, respectively.

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 being moved 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, and even when the object to be measured 28 is moved up and down due to vibrations of the moving table 34, etc. 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 is averaged out and has almost no effect on the displacement of the reflection position. That is, the displacement of the reflection position of the laser beam Lp on the surface 30 is the displacement d due to the unevenness of the surface 30 and the displacement d due to the vibration of the entire object to be measured 28, etc.
The total displacement amount (a + d") is the laser beam.

The amount of displacement DR of the reflection position on the surface 30 is the amount of displacement d° of the entire object to be measured 28 due to vibration or the like.

Laser light reflected from surface 30 and beams.

is passed through the bifocal lens 42 in reverse and transmitted through the non-polarized beam splinter 40, and is then transmitted through the polarized beam splinter 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 light transmitted through the polarization beam splinter 46 is made into convergent light by the condenser lens 22, and then is made incident on the splitting prism 12. This splitting prism 12 is arranged such that the ridgeline 13 formed by its pair of refracting surfaces is perpendicular to the optical axis j and perpendicular to the plane of the paper, and in FIG. By refracting the right half and left half light beams in directions opposite to the optical axis j, two laser beams LP1. Divide into LP2. In this embodiment, the dividing prism 12 and the condensing lens 22 correspond to a measurement optical element, and the ridgeline 13 corresponds to a straight line orthogonal to the optical axis of the measurement light.

One of the light beams LFI is focused on the center of the two-split optical sensor 14 located at a position spaced to the left from the optical axis j, and the other light beam LP2 is focused to the right from the optical axis j. The light is focused on the center of the two-split optical sensor 16 arranged at a distance. The distance between these two-split optical sensors 14 and 16 and the condensing lens 22 is such that when the laser light incident on the condensing lens 22 is parallel light, that is, the distance between the laser beam LP irradiated onto the object to be measured 28 is When the beam waist of the laser beam substantially coincides with the surface 30, the focusing positions of the laser beams LPII L;z are set to coincide with the centers on the two-split optical sensors 14 and 16, respectively.

The two-split optical sensor 14 is disposed straddling both sides of the traveling direction of the laser beam LPI, that is, both the right side and the left side of the plane that includes the straight line m in FIG. 1 and is perpendicular to the paper surface. and the laser beam LP on both sides
A pair of light receiving sections 15a, 15 that respectively detect the amount of light of I
It is equipped with b.

Furthermore, the two-split optical sensor 16 is disposed straddling both sides of the traveling direction of the laser beam LP2, that is, both the left and right sides of the plane including straight line n in FIG. 1 and perpendicular to the paper surface. and a pair of light receiving sections 17a that respectively detect the light intensity of the laser beam LP2 on both sides thereof.
, 17b. And those laser beams L p
+ and L p 2 coincide with the centers on the two-split optical sensors 14 and 16, respectively, the detection output of the amount of light received by the light receiving section 15a15b and the detection output of the amount of light received by the light receiving section 17a17b are They are adjusted so that they are approximately equal. The above two-split optical sensor 1
4 and 16 correspond to measurement optical sensors.

Here, the laser beam reflected by the convexly displaced minute range portion of the surface 30 becomes a divergent state after passing through the bifocal lens 42, and the laser beam is condensed by the condensing lens 22 and the splitting prism 12. Since the condensing positions of the lights L□ and Lp□ are far from the center positions on the two-split optical sensors 14 and 16, respectively, the laser beams LPI+LZ are mainly irradiated on the inner side near the optical axis j, and the light receiving portion 1
The measurement signal Sa obtained by adding the detection outputs of the light receiving sections 15b and 17b becomes large, while the measurement signal sb obtained by adding the detection outputs of the light receiving sections 15b and 17b 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 other hand, the laser beam p reflected by the concavely displaced minute range of the surface 30 becomes convergent after passing through the bifocal lens 42, and the laser beam is condensed by the condenser lens 22 and the splitting prism 12. Hikari LPII L
Since the condensing position of P2 is closer to the position on the two-split optical sensor 14, 16, the laser beam LPI+LP
2 is mainly irradiated on the outside far from the optical axis J, and the measurement signal Sa is obtained by adding the detection outputs of the light receiving sections 15a and 17a.
becomes small, while the measurement signal sb, which is the sum of the detection outputs of the light receiving sections 15b and 17b, 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 laser beam reflected by the polarizing beam splinter 46 is converged by a condensing lens 58 similar to the condensing lens 22, and is then converged by the dividing prism 1.
The light is made incident on a splitting prism 48 similar to 2. This splitting prism 48 is disposed such that a ridgeline 49 formed by its pair of refracting surfaces is orthogonal to the optical axis and perpendicular to the plane of the paper, and the laser beam with respect to the optical axis k in FIG.
By refracting the lower and upper halves of the light beams in directions opposite to the optical axis/k, they are divided into two laser beams Ls++Ls□ that intersect with each other. In this embodiment, the dividing prism 48 and the condensing lens 58 correspond to a reference optical element, and the ridge line 49 corresponds to a straight line perpendicular to the optical axis of the reference light.

One of the light beams is focused on the center on a two-split optical sensor 50 disposed at a position spaced upward from the optical axis k,
The other beam, □, is focused on the center of the two-split optical sensor 52, which is disposed at a position spaced downward from the optical axis k. The distance between these two-split optical sensors 50 and 52 and the condensing lens 58 is such that when the laser beam L's incident on the condensing lens 58 is parallel light, that is, when the laser beam L's incident on the condensing lens 58 is irradiated onto the object to be measured 28, When the beam width and width of the laser beam are substantially aligned with the surface 30, the convergence positions of the laser beams L□ and L are divided into two, respectively, by the optical sensor 5.
It is set to match the center on 0 and 52.

The two-split optical sensor 50 is disposed straddling both sides in the traveling direction of the laser beam LSI, that is, both the lower side and the upper side of the plane that includes the straight line t in FIG. 1 and is perpendicular to the paper surface. and the laser beam L on both sides
A pair of light receiving sections 51a and 5 that respectively detect the light amount of st.
1b.

Further, the two-split optical sensor 52 straddles both sides of the traveling direction of the laser beam L8□, that is, both the upper side and the lower side including the straight line U in FIG. A pair of light receiving sections 53a are arranged and detect the amount of laser light and light on both sides thereof, respectively.
, 53b.

Since the beam waist of the laser beam by 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, and the laser beam is emitted from the bifocal lens 42. Light L'lI+ L12
Since there is a difference in the amount of light received above and below the straight lines t and u, a bias corresponding to this difference in light amount is applied to the light receiving sections 51a, 51b and the light receiving sections 53a, 53b in advance. The difference between the detection outputs is set to zero when the beam waist of the laser beam LP is substantially aligned with the surface 30.

The two-split optical sensors 50 and 52 correspond to reference optical sensors.

Here, when the surface 30 is entirely displaced upward, the laser light is reflected from a relatively wide range of the surface 30,
The divergence state is expanded in accordance with the above displacement, and the laser beam is focused by the condensing lens 58 and the splitting prism 48; Since the converging positions of L and t are each farther away than before, The difference between the irradiation amount on the inside near the optical axis k and the irradiation amount on the outside far from the optical axis k becomes larger than before. Light receiving section 5 at this time
1a.

The reference signal SRa obtained by adding the detection output of 53a and the light receiving section 5
The increase in the difference from the reference signal SRb obtained by adding the detection outputs of 1b and 53b corresponds to the amount of upward displacement of the entire surface 30.

Conversely, when the surface 30 is entirely displaced downward, the laser light reflected from a relatively wide range of the surface 30 is
The divergence state is reduced in accordance with the above displacement, and the light condensing position where the light is condensed by the condenser lens 58 and the splitting prism 48 is closer than before, so that the irradiation amount and the light inside near the optical axis k are The difference with the irradiation amount on the outside far from the axis k becomes smaller than before. At this time, the decrease in the difference between the reference signal SRa, which is the addition of the detection outputs of the light receiving sections 5.1a and 53a, and the reference signal SRb, which is the summation of the detection outputs of the light receiving sections 51b and 53b, is due to the decrease in the downward direction of the entire surface 30. It corresponds to the amount of displacement.

Then, the measurement signals Sa, Sb and the reference signals SRa, SRb are supplied to the measurement circuit 54. The measurement circuit 54 is configured with, for example, a microcomputer, and performs signal processing according to a predetermined program to take the difference between the measurement signals Sa and Sb and the difference between the reference signals SRa and SRb. 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 determined by determining the relationship between the reflection position of the laser beam, Ls, and the differential signals e and Re through experiments and the like. This measuring circuit 54 corresponds to measuring means.

Here, the differential signal e between the measurement signals Sa and sb is the displacement amount 4, which is the sum of the displacement amount d' due to vibration of the entire object to be measured 28 and the displacement amount d due to the unevenness of the surface 30. ~(d+d'), and the reference signals SRa and S
Since the differential signal Re with respect to Rb corresponds to the displacement D1, that is, the displacement position d° due to vibration of the entire object to be measured 28,
The difference between these differential signals e and Re corresponds to the amount of displacement d due only to the unevenness of the surface 30 of the object to be measured 28, and the influence of external disturbances such as vibrations is canceled out, so that the unevenness of the surface 30 can be detected with high accuracy. be measured.

In addition, in the measuring device of this embodiment, the two-split optical sensor 14.1
6 and 50.52 are used, and the laser beam, L, reflected on the surface 30 is focused by the condensing lens 22.58 and refracted and divided by the splitting prism 12.48. The light intensity of the laser beams LPI, LP2, and LSI+ Ls2 is increased or decreased reciprocally in accordance with the movement of the respective condensing positions back and forth as the reflection position is displaced. Since the received light is detected respectively, and the differential output of the partial summation of these is obtained, 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, the unevenness of the surface 30 is measured from the difference between the differential signals e and Re. A driving device is provided to separate the differential signals e and R.
It is also possible to feedback-control the driving device so that one of e becomes zero, and to determine the unevenness of the surface 30 only from the other of the differential signals Re and e.

Also, the condenser lens 2 is adjusted so that the change in the differential signal e becomes zero.
2 and the two-split optical sensors 14 and 16 are moved relative to each other in the direction of the optical axis j, and the condenser lens 58 and the two-split optical sensors 50 and 52 are moved along the optical axis so that the change in the differential signal Re becomes zero. It is also possible to make relative movements in the directions and measure the unevenness of the surface 30 based on the difference in the amount of movement.

Further, in the embodiment described above, the laser beam is always incident on the condensing lens 58 in a diverging state, and the distance between the condensing lens 58 and the two-split optical sensors 50 and 52 is equal to the focal length of the condensing lens 58. However, in a state where the beam waist of the laser beam substantially coincides with the surface 30, the two-split beam is focused by the condensing lens 58 at a position that substantially coincides with the condensing position of the laser beam. sensor 50
52, or another condensing lens may be arranged between the polarizing beam splinter 46 and the condensing lens 58 in order to make the laser beam parallel to the beam before it enters the condensing lens 58. In this case, there is no need to apply a predetermined bias to the light receiving sections 51a, 51b, and 53a, 53b of the two-split optical sensors 50 and 52.

Furthermore, in the embodiment described above, the laser beam that exits the beam expander 20 and becomes a parallel beam with a circular cross section is made incident on the bifocal lens 42, but it is configured such that the laser beam is in the form of convergent light or diverging light. Laser light with bifocal lens 42
It is also possible to make the light incident on . In that case, surface 3
Other lenses may be provided between the polarizing beam splinter 46 and the condensing lens 22 and 58 so that the laser beams LP and LS reflected at The two-split optical sensors 14, 16 and 50.52 may be respectively arranged at the light focusing positions where the light is focused by .58.

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.

Furthermore, in the embodiment, each pair of laser beams LPII LP□ and L S I +L are refracted and split by the splitting prisms 12 and 48, respectively.
The light intensity of 5□ was detected by the two-split optical sensors 14.16 and 50.52, respectively, but the laser beam Lp
It is only necessary to detect the change in the amount of light by refracting and focusing at least half of each luminous flux, and it is not necessary to use a splitting prism 12.48 or a pair of two-split optical sensors 14, 16, and 50. ．．
52 is not necessary.

Further, in the embodiment, the splitting prism 12 and the condensing lens 22 are used as the measuring optical element and the reference optical element.
, the splitting prism 48, and the condensing lens 58 have been used, but it is also possible to configure the measuring optical element and the reference optical element using other optical components such as a concave mirror.

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 splitting prism and a condensing lens. FIG. 3 is a schematic diagram illustrating an example of a conventional optical surface roughness measuring device using a splitting prism and a condensing lens. 13: 14°28 = 42: 44: Ridge line (straight line) 16: 2-split optical sensor (measurement optical sensor) object to be measured
30: Surface bifocal lens (objective lens) Light source device 46: Polarizing beam splinter 111all1 49: Edge! (straight line) 50.52: 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 reflected by the surface and passed through the objective lens; and an optical axis of the measurement light separated by the polarization beam splitter. Reflection of the measurement light on the surface by refracting at least half of the line bordering the orthogonal line and condensing the light at a position away from the optical axis on a plane that includes the optical axis and is perpendicular to the line. a measurement optical element that moves the convergence position of the refracted measurement light back and forth in its traveling direction as the convergence/divergence state of the measurement light is changed according to positional displacement; Measuring lights that are disposed on both sides of the measurement light refracted by the optical element in the traveling direction and detect the amount of the measurement light that reciprocally increases or decreases in response to movement of the focusing position of the measurement light. refract at least half of the reference light separated by the sensor and the polarizing beam splitter, with a straight line perpendicular to the optical axis, and from the optical axis on a plane that includes the optical axis and is perpendicular to the straight line; By condensing the light at separate positions, 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, and the convergence position of the refracted reference light changes. a reference optical element that moves the reference light back and forth in its traveling direction; a reference light sensor that detects the amount of light of the reference light that increases and decreases reciprocally, and a measurement signal output from the measurement light sensor;
An optical surface roughness measurement method characterized by having a measuring means for taking a differential of the reference signals output from the reference optical sensor and measuring the unevenness of the surface based on the difference between the differential signals. measuring device.