JPH0739946B2 - Surface condition inspection device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a surface condition inspection apparatus, and more particularly to an improvement of a surface condition inspection apparatus for optically inspecting the surface condition of a surface to be inspected.

[Prior Art] Today, the surface condition of various products is widely inspected and measured in various fields. In order to perform such inspection and measurement efficiently and accurately, various surface condition inspection devices have been conventionally used. Proposals and practical applications have been made.

As one of the conventional devices of this type, for example, JP-A-59-1439.
The device related to No. 09 is well known, and this conventional device measures the surface state of the surface to be inspected based on the amount of reflected light.

However, in such a conventional device, accurate measurement cannot be performed unless the tilt angle and the distance of the probe that projects and receives light with respect to the object surface are always kept constant, and the handling thereof is very troublesome. there were.

An example of such a conventional device is shown in FIG. 15, which comprises a set of optical systems arranged at an angle Θ.
Each of the optical systems 10 and 12 has a light projecting axis and a light receiving axis formed in a coaxial structure, and projects the inspection light from the light source 14 to the surface 16 to be inspected through the optical system 10. It is shining.

Further, the reflected light from the surface 16 to be inspected is received by using the optical systems 10 and 12, and photoelectrically converted by the sensors 18 and 20 and input to the arithmetic unit 22.

Then, the arithmetic unit 20 determines the surface 1 to be inspected based on the ratio (FΘ / F0) of the input signals (FΘ, F0) from the sensors 18 and 20.
The surface roughness of 6 is measured.

By the way, the projected light shows a peculiar reflection intensity distribution according to the roughness of the surface 16 to be inspected, and one of the reflected light is perpendicular to the surface 16 to be inspected and the other is at an angle Θ. When the light is received with, a difference appears between the two received light amounts.

That is, as shown in FIG. 16A, when the projection axis is set to be perpendicular to the surface 16 to be inspected, the optical system 10 coaxial with the projection axis is provided.
The amount of received light Fo1 obtained from is the optical system 1 that forms an angle Θ with the projection axis.
It is larger than the received light amount FΘ1 obtained from 2.

Therefore, the surface roughness of the surface 16 to be inspected can be known by obtaining the ratio of the amount of light received by each of the optical systems 10 and 12.

[Problems to be Solved by the Invention] However, in such a conventional apparatus, when the inclination of the projection axis is not perpendicular to the surface 16 to be inspected, the reflection intensity distribution f is as shown in FIG. 16 (b). become.

Therefore, at this time, the received light amount Fo obtained from one optical system 10
2 becomes a value smaller than the received light amount Fo1, and the received light amount FΘ2 obtained from the other optical system 12 is the received light amount FΘ1.
It will be a larger value.

Therefore, even if the surface state of the inspected surface 16 is the same, if the projection axis is tilted and is not perpendicular to the inspected surface 16, each optical system 10,
The received light amount ratio obtained from 12 has a different value each time, and there is a problem that the surface state of the surface 16 to be inspected cannot be accurately measured.

OBJECT OF THE INVENTION The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a surface to be inspected without being influenced by the magnitude and direction of the inclination of the projection axis with respect to the surface to be inspected. An object of the present invention is to provide a surface condition inspection device capable of accurately inspecting the surface condition.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the apparatus of the present invention comprises: a projection optical system for guiding inspection light to a surface to be inspected; and a light receiving surface formed in a coaxial structure with the optical system. , A main optical system for receiving the reflected light from the surface to be inspected, and a ring-shaped arrangement around the light emitting axis at equal intervals so that the light receiving axis is inclined at a predetermined angle with respect to the light emitting axis. A plurality of compensating optical systems for receiving the reflected light from the surface, and an arithmetic means for adding the outputs of the respective light receiving optical systems and outputting a signal representing the surface state of the surface to be inspected. The surface condition of the surface to be inspected is not affected by the inclination between the surface and the surface to be inspected.

Hereinafter, the constitution of the present invention will be described more specifically.

FIG. 1 shows the detailed structure of the optical system. The apparatus according to the present invention is constructed by a first optical system 100 and a second optical system 2.
It is composed of 00 and.

The first optical system 100 applies the inspection light from the light source 14 to the surface 16 to be inspected.
And a main light receiving optical system 32 for receiving the reflected light from the surface 16 to be inspected.

The light receiving main optical system 32 is configured so that its light receiving axis has a coaxial structure with the light projecting axis of the optical system 30.

Further, the second optical system 200 is configured by using a plurality of compensating optical systems which are arranged in a ring shape at equal intervals around the light projecting optical system 30 and receive the reflected light from the surface to be inspected. Is
Four compensating optical systems 40, 42, 4 arranged in a ring at equal intervals
It is composed of 4, 46.

Each of the compensating optical systems 40, 42, 44 and 46 is installed so that the light receiving axis thereof is inclined by a predetermined angle Θ with respect to the light projecting axis of the optical system 30.

Therefore, in the figure, the optical systems 40 and 44 correspond to the optical system 30.
It will be arranged in the yz plane so as to face each other across. Further, the optical systems 42 and 46 are arranged in the xz plane so as to face each other with the optical system 30 interposed therebetween.

Further, FIG. 2 shows a specific configuration of the calculating means, and the light received by each of the optical systems 32, 40, 42, 44 and 46 is
The photoelectric conversion means 50, 52, 54, 56, 58 are used to convert the signals into electrical signals, which are then added by the adding means 60 and output as signals representing the surface state of the surface 16 to be inspected.

Further, in the present invention, a plurality of subtracting means for calculating the difference between the outputs of the compensating optical system that opposes each other across the projection axis is provided, and the inclination of the projection axis with respect to the surface to be inspected based on the output of each subtracting means. It is preferable to determine the angle.

In the figure, subtraction means 62 for calculating the difference between the outputs of the compensation optical systems 40 and 44 and subtraction means 64 for calculating the difference between the outputs of the compensation optical systems 42 and 46 are provided, and the division means
The output (Vd) of the adding means 60 is converted into the subtracting means 62,
By dividing by 64 output (Vs), the projection axis and the surface to be inspected
The degree of inclination with 16 is measured.

[Operation] The present invention is configured as described above, and the operation will be described below.

First, as shown in FIG. 3 (a), the first optical system 100 is used to inject the inspection light emitted from the light source 14 into the projection optical system 30.
Perpendicular to the surface 16 to be inspected through (this state is called inclination 0)
Main optical system for receiving the reflected light from the surface 16 to be inspected
Light is received by 32.

At this time, the light projected on the surface 30 to be inspected has specific reflection characteristics (regular reflection light, diffuse reflection light, and absorption at present) depending on the surface state.

That is, when the surface is smooth, the intensity of specular reflection light is large and the distribution is sharp. On the contrary, when the surface is rough, the intensity of specular reflection light is small and the distribution is wide.

From this, the surface state of the surface 16 to be inspected can be known by measuring the peak value and distribution of the intensity of specular reflection light.

However, in order to accurately measure the peak value and distribution of the reflection intensity using only the first optical system 100, it is necessary to set the inclination between the projection axis and the surface 16 to be inspected to zero. . If this relationship is broken, for example, if the inclination is not 0 as shown in FIG. 3 (b), the shape of the reflection intensity distribution is broken and the measured value fluctuates, which makes accurate measurement impossible.

However, when performing a manual measurement, it is difficult to fix the inclination between the projection axis and the surface 16 to be inspected, and particularly when a free-form surface is set as the measurement target, measurement is performed while maintaining this relationship. It is extremely difficult, and the measurement tends to be inaccurate in the normal specification measurement.

The characteristic feature of the present invention is that by using the first optical system 100 in combination with the second optical system 200, even when the inclination is not 0, the amount of light received is the same as when the inclination is 0, regardless of the inclination direction. Therefore, the surface condition of the surface 16 to be inspected can be accurately measured even when the normal specification measurement is performed.

In FIG. 1, the second optical system 200 is composed of four compensating optical systems 40, 42, 44 and 46, which are arranged in a ring shape at equal intervals around the projection axis and have a predetermined length with respect to the projection axis. Slope of
Is inclined at.

Therefore, when the inclination is 0 as shown in FIG. 4 (a), the second optical system 200 only receives so-called diffuse reflection light having a small reflection intensity outside the peak of the reflection intensity distribution. . Therefore, the amount of received light is small, and the amount of received light on each of the light receiving shafts 40, 42, 44, 46 is uniform.

Then, as shown in FIG. 4B, when the inclination is not 0, the peak of the reflection intensity moves in the direction of the optical system arranged in the inclination direction, so the amount of light received by the optical system arranged in the inclination direction. Will increase. This increase is equivalent to the decrease in the amount of light received by the first optical system 100 that is decreased by tilting, and the signal obtained by the second optical system 200 and the signal obtained by the first optical system are equal to each other. By adding, it is possible to eliminate the fluctuation of the received light amount due to the inclination of the projection axis and the surface 16 to be inspected, that is, the fluctuation of the measured value. In this way, the apparatus of the present invention uses the first optical system 100 and the second optical system 200 in combination to change the magnitude and direction of the inclination between the projection axis and the surface 16 to be inspected. Even in this case, the surface condition of the surface 16 to be inspected can be accurately measured.

Further, in the present invention, each division means 66, 68 is an addition means.
The added value of the outputs of all the photoelectric conversion means 50, 52, ... 58 output from 60 is divided by using the subtraction value output from the corresponding subtraction means 62, 64, and the projection axis and the surface to be inspected are divided. Of the probe A and the surface to be inspected 16 (inclination in the xz plane) and β (inclination in the yz plane) as shown in FIG. You can

[Effects of the Invention] As described above, according to the present invention, even if the magnitude and direction of the tilt between the projection axis and the surface to be inspected changes, the amount of received light is constantly compensated, and the surface state of the surface to be inspected Has an effect that can be accurately measured.

[Embodiment] Next, a preferred embodiment of the present invention will be described with reference to the drawings. The members corresponding to those of the apparatus shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

First Embodiment FIG. 5 shows a preferred embodiment of the surface state inspection apparatus according to the present invention. The apparatus of the embodiment is an optical system for projecting and receiving inspection light toward the surface 16 to be inspected. Probe A with built-in
And a signal processing circuit B for determining the surface state of the surface 16 to be inspected based on the signal from the probe A.

As shown in FIG. 1, the probe A is a projection optical system that guides the inspection light output from the light source 14 and projects it onto the surface 16 to be inspected.
30 and optical systems 32, 4 for receiving the reflected light from the surface 16 to be inspected
Contains 0, 42, 44 and 46.

6 (a) and 6 (b) show a specific configuration of the probe A, and the optical systems 30, 32, 40, ... 46 are each formed by using an optical fiber, The inspection light emitted from the light source 14 provided on the optical system is projected toward the surface 16 to be inspected through the optical system 30 for projection formed by using an optical fiber, and the reflected light from the surface 16 to be inspected uses an optical fiber. Optical system 32, 40, 42, ... 48 for each light reception formed by
Is received using.

At this time, specular reflection light and diffuse reflection light are mixed in the reflection light from the surface 16 to be inspected, and the reflection intensity distribution is
It changes according to 16 surface conditions.

In the embodiment, the main optical system 32 for receiving light is the optical system 30 for projecting light.
Is formed so as to have a coaxial structure, and is formed so as to mainly receive specularly reflected light from the surface 16 to be inspected.

The remaining compensating optical systems 40, 42, ... 46 are annularly arranged at equal intervals around the light receiving axis so that the light receiving axis is inclined at a predetermined angle θ with respect to the light projecting axis. Therefore, each of these optical systems 40, 42, ... 46 mainly receives the diffuse reflection light from the surface 16 to be inspected.

FIG. 7 shows a specific mounting structure of each of the optical systems 30, 32, 40, 42, ... 46. FIG. 7A is a sectional view of the probe A, and FIG. It is the top view.

As shown in the figure, it has a coaxial structure on one end side that constitutes the light projecting surface and the light receiving surface and branches into two at the other end side, one of which branches to the light source 16 and the remaining one. Are connected to the signal processing circuit B.

FIG. 8 shows a specific configuration of the signal processing circuit B. The signal processing circuit B includes photoelectric conversion circuits 50, 52, ...
58, an adding circuit 60 and a display circuit 62.

Then, the optical signals received by using the light receiving optical systems 32, 40, 42, ... 46 are converted into electrical signals by using the photoelectric conversion circuits 50, 52, ... 58, and the electrical signals are further added. The value is added using 60 and the added value is displayed on the display circuit 62.

Using the surface condition inspection apparatus of this example, an experiment was conducted to find out how the inclination between the projection axis and the surface 16 to be inspected affects the measured value. I was able to get

The measurement was performed by first applying the probe A to the surface 16 to be inspected and operating the measurement switch button attached to the probe A.

As a result of this measurement, the compensation optical system 40, 42,
When the projection axis and the surface to be inspected are tilted without using 46, the fluctuation of the measured value is 20% / ± 5 °, whereas the compensation optical system as in the present invention is used. It was confirmed that the fluctuation of the measured value could be reduced to 2.5% / ± 5 ° when 40, 42, ... 46 were used.

As is clear from this experimental result, according to the present invention, the surface state of the surface 16 to be inspected can be accurately inspected without being affected by the magnitude and direction of the inclination between the projection axis and the surface 16 to be inspected. It will be understood that there is.

Measurement Experiment Further, the inventor of the present invention conducted a measurement experiment using three types (O, P, Q) of the inspected surfaces 16 having different surface states, using the apparatus of the embodiment. Here, the surface 16 to be inspected as a sample is roughened in the order of O, P, and Q.

The experiment was performed by projecting the inspection light onto the surface 16 to be inspected at an incident angle of 20 degrees as shown in FIG.

FIG. 10 shows the scanning angle based on the incident angle of the light to be inspected,
Data obtained by measuring the reflected light from the surface 16 to be inspected is shown (at this time, the reflection angle of the specularly reflected light included in the reflected light is
Since it becomes 20 degrees, the reflected light shows a peak value when the scanning angle is 40 degrees).

As is clear from the measurement data of O, P, and Q shown in the figure, if the surface state of the surface 16 to be inspected is different, the reflection pattern and the peak value are also different.

Moreover, since the light receiving amounts of O and P are almost equal near the scanning angle of 48 degrees, and the light receiving amounts of O and Q are almost equal near the scanning angle of 53 degrees, the conventional compensation optical system is used. In the non-apparatus, if the inclination with respect to the surface 16 to be inspected is different, the measured data will have different values and accurate inspection cannot be performed.

11 to 13 show measurement data obtained by using the apparatus of the present embodiment, and FIG. 11 shows all the light receiving optical systems 32, 40, 42 output from the adding circuit 60. Fig. 12 shows the total amount of light received by 44 and 46, and Fig. 12 shows the amount of light received by the main optical system 32 for receiving light.
FIG. 13 shows the total amount of light received by the compensation optical systems 40, 42, 44, and 46. Here, the inclination of the horizontal axis is represented with a scanning angle of 40 degrees (light receiving angle of specular reflection light) as a reference.

For the convenience of the experiment, the inspection light shown in FIG. 9 was projected using an optical system different from the projection optical system 30 of the apparatus of this embodiment.

As is clear from this experiment, when the inclination of the apparatus of this embodiment is increased, the amount of light received by the main optical system 32 for light reception decreases as shown in FIG. 12, but the compensation optical systems 40, 42, 44, The total amount of light received by 46 increases as shown in FIG. Therefore, all the light receiving optical systems 32, 40, 42, 44 output from the adder circuit 60,
As shown in FIG. 11, the total amount of light received by 46 is a constant value that is not affected by the inclination up to around 7 degrees, and O, P, Q
The sample data of does not intersect with other sample data.

This means that if the apparatus of the embodiment is used, the surface condition of the surface 16 to be inspected can be accurately inspected even if the apparatus is tilted 7 degrees in any direction, and the conventional apparatus having an allowable tilt angle of about 1 degree. It can be understood that the degree of freedom of the measurement posture is so large that it cannot be compared with.

Therefore, according to the present embodiment, the surface condition of the surface 16 to be inspected can be accurately inspected without being affected by the magnitude and direction of the inclination with respect to the surface 16 to be inspected.

Further, according to the present embodiment, as shown in FIG. 11, the differences Δop and Δpq in the received light amounts of O, P and Q are substantially constant even if the inclination becomes large. Therefore, for example, when the type of the surface 16 to be inspected is specified as O, P, Q, O, P, P
If the differences Δop and Δpq in the amount of received light between Q and Q are measured in advance, the surface condition of the surface 16 to be inspected can be inspected also from the difference in the amount of received light.

Second Embodiment FIG. 14 shows a second preferred embodiment of the surface condition inspection apparatus according to the present invention.
An embodiment is shown, and the characteristic feature of this embodiment is that the signal processing circuit B is provided with an inclination detecting means for detecting the inclination of the projection axis with respect to the surface 16 to be inspected.

In the embodiment, this inclination detecting means is the photoelectric conversion circuit 5
The outputs of 0, 52 and 56, 58 are subtracted by subtraction circuits 62, 64, respectively, and the subtracted values are output to the corresponding division circuits 66, 68.

Then, each division circuit 66, 68 uses the addition value of the output of all photoelectric conversion circuits 50, 52, ... 58 output from the addition circuit 60, and the subtraction value output from the corresponding subtraction circuit 62, 64. And the inclination between the projection axis and the surface to be inspected, that is, as shown in FIG.
The inclination in the plane) and β (inclination in the yz plane) are calculated.

The tilt angles α and β calculated in this way are displayed using the tilt angle display circuits 70 and 72, and the comparison circuit
The inclination angle calculated using 74 and 76 is monitored so that it does not exceed the specified reference value, and an alarm signal is generated when the inclination angles α and β exceed the reference value, and the surface condition due to the inclination angle being too large. The occurrence of inspection errors is prevented.

Further, such an alarm signal can be displayed using the monitors 70 and 80 so that the alarm signal can be visually confirmed.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a surface condition inspection apparatus according to the present invention, FIG. 2 is a block circuit diagram showing an example of a calculation means used in the present invention, and FIG. 3 is an explanation of a measurement principle of a first optical system. FIG. 4A is an explanatory view when the inclination angle between the light projecting axis and the light receiving surface is 0, and FIG. 7B is an explanatory view when the light projecting axis and the surface to be inspected are tilted, FIG. 4 is an explanatory view of the measurement principle of the present invention, and FIG.
Is an explanatory view when the inclination angle of the light emitting axis with respect to the light receiving surface is 0, FIG. 7B is an explanatory view when the light emitting axis and the surface to be inspected are inclined, and FIG. 5 is a surface according to the present invention. FIG. 6 is an explanatory view showing a first preferred embodiment of the state inspection device, FIG. 6 is an external view explanatory diagram of a probe used in the device shown in FIG. 5, and FIG. b) is a side view thereof, FIG. 7 is an explanatory view of a light projecting surface and a light receiving surface of the probe shown in FIG. 6, and FIG. 7A is a side sectional view of the probe tip, FIG. Is a plan view of the tip of the probe, FIG. 8 is an illustration of the signal processing circuit used in the first embodiment shown in FIG. 5, and FIG. 9 is an illustration of a measurement experiment conducted using the apparatus of the first embodiment. , Fig. 10 is a characteristic diagram obtained by measuring the relationship between the scanning angle and the reflection intensity distribution for each sample, with each sample of O, P and Q as the surface to be inspected. 11 to 13 are characteristic diagrams obtained by measuring the amount of received light while changing the inclination using the device of the first embodiment, and FIG. 14 shows a preferred second embodiment of the present invention. Explanatory drawing, FIG. 15 is a block diagram showing an example of a conventional surface condition inspection apparatus, FIG. 16 is an explanatory view of the measurement principle of the conventional apparatus shown in FIG. 15, and FIG. FIG. 3 is an explanatory diagram when the inclination angle with the light receiving surface is 0, and FIG. 6B is an explanatory diagram when the projection axis and the surface to be inspected are inclined. 14 ... Light source 16 ... Surface to be inspected 30 ... Projection optical system 32 ... Receiving main optical system 40, 42, 44, 46, 48 ... Compensation optical system 50, 52, 54, 56, 58 ...... Photoelectric conversion means 60 ...... Addition means 62, 64 ...... Subtraction means 66, 68 ...... Division means 100 ...... First optical system 200 ...... Second optical system

Claims (4)

[Claims] 1. A light projecting optical system for guiding inspection light to a surface to be inspected, and a main optical system for receiving light which has a light receiving surface formed in a coaxial structure with the optical system and receives reflected light from the surface to be inspected. , A plurality of compensating optical systems which are arranged in a ring shape at equal intervals around the projection axis so that the reception axis is inclined at a predetermined angle with respect to the projection axis, and which receive the reflected light from the surface to be inspected; And a calculation means for adding the output of the optical system for receiving light and outputting a signal indicating the surface state of the surface to be inspected, and A surface condition inspection device for inspecting the condition. 2. A surface condition inspection apparatus according to claim 1, wherein four compensating optical systems are arranged in a ring shape at equal intervals around the projection axis. 3. The apparatus according to claim 1, wherein the arithmetic means subtracts the outputs of compensating optical systems facing each other with the projection axis interposed therebetween. And a surface state inspecting apparatus for determining an inclination angle of a projection axis with respect to a surface to be inspected based on an output of each subtraction circuit. 4. The apparatus according to any one of claims (1) to (3), wherein the computing means outputs an alarm signal when the detected tilt angle exceeds a predetermined reference angle. Characteristic surface condition inspection device.