JP4679313B2 - Surface smoothness measuring device - Google Patents

Description

  The present invention relates to a surface smoothness measuring apparatus.

  Conventionally, when measuring the surface roughness of an object such as a plastic film, that is, the surface smoothness, an apparatus has been used that performs measurement by sliding a contactor that contacts the surface of the object. However, in such an apparatus, since the contact contacts the surface of the object to be measured, the object surface may be damaged.

In view of this, an apparatus that measures the surface smoothness of an object in a non-contact manner using an optical measuring instrument has been proposed (see, for example, Patent Document 1). In this case, the surface of the object is irradiated with measurement light, and the surface smoothness of the object is measured in a non-contact manner using the reflected light.
JP-A-5-340747

  However, in the conventional surface smoothness measuring apparatus, since the measurement light is a spot beam with a narrow irradiation range, it takes time and effort to measure the surface smoothness of the entire surface of the object.

  The present invention solves the problems of the conventional surface smoothness measuring apparatus, irradiates the object surface with irradiation light of a specific pattern, and smoothes the object surface based on the received light intensity distribution of the reflected light from the object surface. It is an object of the present invention to provide a surface smoothness measuring apparatus that can measure the smoothness of various object surfaces stably, accurately, quickly, and easily.

For this purpose, in the surface smoothness measuring apparatus of the present invention, a light source that irradiates light on the surface of an object and a light source that is provided between the object and the light source and that irradiates the object from the light source in a predetermined direction. A light shielding means for shielding light so as to form a specific pattern, a light receiving means for receiving reflected light reflected from the surface of the object, and a received light intensity distribution for each position in a predetermined direction based on the light received by the light receiving means. A received light intensity distribution detecting means for detecting; and a smoothness calculating means for calculating the smoothness of the object surface based on the received light intensity distribution detected by the received light intensity distribution detecting means, wherein the light shielding means shields light. A light transmitting portion that transmits light, and the light transmitting portions are arranged alternately at predetermined intervals in a concentric manner, shielding the irradiation light so as to form a concentric striped pattern, the smoothing degree calculating means Calculating a plurality of directions of smoothness based on the maximum and minimum values obtained from a plurality of directions of the light-receiving intensity distribution.

  According to the present invention, the surface smoothness measuring apparatus irradiates the object surface with irradiation light of a specific pattern, and calculates the smoothness of the object surface based on the received light intensity distribution of the reflected light from the object surface. Yes. Therefore, the smoothness of various object surfaces can be measured stably, accurately, quickly and easily.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram of a surface smoothness measuring apparatus according to a first embodiment of the present invention, FIG. 2 is a diagram showing a pattern projection plate according to the first embodiment of the present invention, and FIG. It is a block diagram which shows the structure of the signal processing apparatus in the embodiment.

  The surface smoothness measuring apparatus in the present embodiment is an apparatus for measuring the surface smoothness of an object made of various materials. As shown in FIG. 1, the pattern projection apparatus 11 and photoelectric conversion as a light receiving means. It has the element 12, and the signal processing apparatus 13 as a received light intensity distribution detection means and a smoothness calculation means. The object to be measured is, for example, a plastic film, but may be a metal plate or any type of any shape.

  Here, the pattern projection device 11 includes a light source 11a and a pattern projection plate 11b as a light shielding unit. The light source 11a is, for example, an incandescent bulb such as a tungsten bulb or a halogen bulb, or a white fluorescent lamp, but may be any type as long as it irradiates light on the surface of an object. Further, the pattern projection plate 11b shields the irradiation light so as to form a linear pattern. For example, as shown in FIG. 2, a stainless steel plate having a thickness of 0.5 [mm] is used. The surface is provided with a shielding portion on which a matte coating is applied so as not to reflect the irradiation light from the light source 11a, and openings 31 as a plurality of light transmission portions. In the example shown in FIG. 2, the number of the opening portions 31 is eight, and each opening portion 31 has a slit shape with a width of 1 [mm] so that the distance between adjacent ones is 1 [mm]. It is arranged. Further, the pattern projection device 11 is held so as to irradiate light at a predetermined angle θ with respect to the object surface 14 as the object surface. Note that the value of θ can be arbitrarily changed depending on the type of the object to be measured and the measuring method, but in this embodiment, θ = 45 degrees.

  In addition, the photoelectric conversion element 12 includes a CCD (Charge Coupled Device) array in which a large number of light receiving elements are arranged linearly (one-dimensionally). The CCD array can be one in which CCDs that are light receiving elements are two-dimensionally arranged, but the photoelectric conversion element 12 in the present embodiment is a CCD array in which light receiving elements are one-dimensionally arranged. Is used. Therefore, the reflected image of the pattern projected on the surface 14 of the object to be measured is converted into an electric signal by each light receiving element, and the reflected light distribution waveform is displayed based on the output value at each position of the light receiving element.

  The photoelectric conversion element 12 is disposed at a position where the reflected light from the projection surface onto which the incident light from the pattern projection device 11 is projected onto the surface 14 to be measured can be detected. The When the angle between the optical axis of the incident light from the pattern projection device 11 and the surface 14 of the object to be measured is θ, the optical axis from the pattern projection device 11 to the projection surface and the projection surface to the photoelectric conversion element 12 are connected. The photoelectric conversion element 12 is disposed at a position where the angle formed by the axis is (180-2θ).

  Further, the output of the photoelectric conversion element 12 is connected to the signal processing device 13. As shown in FIG. 3, the signal processing device 13 includes a receiving unit 21 that receives an electrical signal from the photoelectric conversion element 12, an A / D conversion unit 22 that performs A / D conversion on the electrical signal, and the A / D. The digital signal converted by the conversion unit 22 is subjected to waveform processing, a maximum value (Max) and a minimum value (Min) are selected, and a data analysis unit 23 as smoothness calculation means for calculating smoothness, and reflected light The display unit 24 displays the distribution waveform and the smoothness (S). Here, the maximum value and the minimum value are selected by the data analysis unit 23 from the data obtained in the A / D conversion unit 22.

  The maximum value and the minimum value may be selected by the user instead of the data analysis unit 23. In this case, the signal waveform is displayed, and a message requesting the user to select a maximum value and a minimum value from the signal waveform is displayed on the display unit 24. Then, when the user operates an input unit (not shown) included in the signal processing device 13, the maximum value and the minimum value are input and selected. Here, the maximum value and the minimum value are selected by the user because, for example, the signal waveform is not a sin curve composed of a clean curve, but is a jagged waveform. This is a case where there is a possibility that a value other than 1 may be selected by the data analysis unit 23.

  Next, the operation of the surface smoothness measuring apparatus having the above configuration will be described.

  FIG. 4 is a diagram showing the relationship between the surface smoothness of the surface of the object to be measured and the output of the photoelectric conversion element in the first embodiment of the present invention, and FIG. 5 is the A / D in the first embodiment of the present invention. It is a figure which shows the numerical formula which calculates the average of the converted data and the maximum value of signal waveform, or the minimum value, and the value of smoothness.

  First, a parallel light beam is irradiated from the light source 11a onto the pattern projection plate 11b to project a light / dark pattern of light onto the surface 14 of the object to be measured. Then, a reflected image of the pattern projected on the surface 14 of the object to be measured is picked up by the photoelectric conversion element 12 and converted into an electric signal which is an analog signal.

  Here, the relationship between the physical surface smoothness of the surface 14 to be measured and the output of the photoelectric conversion element 12 will be described. First, a projection pattern having an intensity distribution as shown in FIG. And when the to-be-measured object surface 14 is an ideal smooth plane without an unevenness | corrugation as FIG.4 (b)-(1) shows, a projection pattern is reflected faithfully and the photoelectric conversion element 12 of FIG. As shown in FIGS. 4 (c)-(1), the output has the same received light intensity distribution waveform as the projection pattern of FIG. 4 (a).

  However, as shown in FIGS. 4 (b) to 4 (2), when the measured object surface 14 is a surface having high smoothness but having unevenness, the projected light is scattered by the measured object surface 14. Therefore, the output of the photoelectric conversion element 12 has a received light intensity distribution waveform as shown in FIGS.

  Further, when the object surface 14 is a surface having low smoothness and large unevenness as shown in FIGS. 4B to 4C, the projected light is scattered by the object surface 14 to be measured. Therefore, as shown in FIGS. 4C to 4C, the output of the photoelectric conversion element 12 has a light reception intensity distribution waveform having a low peak and a high valley. In the present embodiment, the smoothness of the surface 14 of the object to be measured is quantified by using the difference in the output waveform of the photoelectric conversion element 12, that is, the received light intensity distribution waveform.

  Subsequently, the output of the photoelectric conversion element 12 is input to the signal processing device 13. The intensity signal input to the signal processing device 13 is A / D converted by the A / D converter 22 and subjected to waveform processing based on the converted digital signal. At this time, the A / D converted and waveform processed data is displayed on the display unit 24 as a received light intensity distribution waveform as shown in FIG.

  Next, average Max (Ave), which is an average value of local maximum values in the received light intensity distribution waveform as shown in FIG. 5A, and an average value of local minimum values in the received light intensity distribution waveform. The average Min (Ave) is obtained. In this case, Max (Ave) and Min (Ave) can be obtained according to equations (1) and (2) shown in FIG. Further, based on the obtained Max (Ave) and Min (Ave), the smoothness (S) is calculated according to the equation (3) shown in FIG. 5B, and the calculation result is displayed on the display unit 24. .

In the present embodiment, the respective average values from the maximum value and the minimum value in the received light intensity distribution waveform as shown in FIG. 5A are expressed by the equations (1) and (2) (FIG. 5 (b)). ) And the smoothness (S) was obtained according to the equation (3) (FIG. 5B). From the received light intensity distribution waveform as shown in FIG. The smoothness (s) may be obtained from the following equation (4) from the value, and the smoothness (S) may be obtained from the average value of the smoothness by the following equation (5).
s (n) = (Max (n) −Min (n)) / (Max (n) + Min (n)) (4)
Smoothness (S) = (Σs (n)) / n (5)
Next, the evaluation of the surface smoothness based on the maximum value and the minimum value shown in the received light intensity distribution waveform will be described.

  FIG. 6 is a diagram showing received light intensity distribution waveforms for two surfaces of objects to be measured having different reflectivities in the first embodiment of the present invention.

  Here, two objects having the same surface roughness, that is, surface smoothness but having different reflectances are measured objects, and reflected light from each measured object surface 14 is received by the photoelectric conversion element 12. The received light intensity distribution waveform obtained by the signal processing device 13 performing waveform processing on the output obtained will be described. 6A shows the received light intensity distribution waveform when the reflectance of the object surface 14 is high, and FIG. 6B shows the received light intensity distribution waveform when the reflectance of the object surface 14 is low. Yes.

  By the way, when the standard deviation between the maximum value and the minimum value in the received light intensity distribution waveform is used to evaluate the surface smoothness of the surface 14 of the object to be measured, in the case of the received light intensity distribution waveform shown in FIG. The deviation value is 2.2. In the case of the received light intensity distribution waveform shown in FIG. 6B, the standard deviation value is 1.1. Thus, when the reflectance is different, the standard deviation value is different even if the surface smoothness is the same. Therefore, depending on the standard deviation between the maximum value and the minimum value in the received light intensity distribution waveform, the surface of the object to be measured It turns out that the surface smoothness of 14 cannot be evaluated appropriately.

  On the other hand, when the smoothness (S) is calculated as described above, in the case of the received light intensity distribution waveform shown in FIG. 6 (a), the value of the smoothness (S) is 0.33. In the case of the received light intensity distribution waveform shown in FIG. 6B, the smoothness (S) value is 0.33. From this, even if the reflectivity is different, absolute surface smoothness is obtained by the equation (3) (FIG. 5B). Therefore, if the surface smoothness is the same, the smoothness ( It can be seen that the values of S) are the same. That is, by using the smoothness (S) as an index of the surface smoothness of the surface 14 to be measured, the surface smoothness of the surface 14 to be measured can be appropriately evaluated.

  Thus, in the present embodiment, the smoothness is calculated, and the smoothness of the surface 14 to be measured is measured based on the smoothness. Therefore, even if there is a difference in the reflectance of the surface 14 to be measured, a change in the light emission intensity of the light source 11a, a change in the sensitivity of the photoelectric conversion element 12, a change in the average level of the received light intensity distribution of the reflected light, etc. In addition, it is not necessary to make corrections for fluctuations in environmental temperature, changes with time of the light source 11a, and the like, and the same measurement value can be obtained stably and constantly with respect to an object having the same surface shape.

  Then, the surface roughness in the linear direction (one-dimensional direction) in which the reflection pattern is detected from the surface 14 of the object to be measured formed by the pattern projection plate 11b can be measured by one measurement.

  In addition, it is possible to directly compare the surface smoothness of substances having different reflectivities, for example, plastic and metal, and it can be expected that the range of use of the surface smoothness measuring apparatus will be expanded.

  Next, a second embodiment of the present invention will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by providing the same code | symbol. The description of the same operation and the same effect as those of the first embodiment is also omitted.

  FIG. 7 is a diagram showing a pattern projection plate according to the second embodiment of the present invention.

  The surface smoothness measuring apparatus in the present embodiment uses a pattern projection plate 41 as a light shielding means having a pattern as shown in FIG. 7 instead of the pattern projection plate 11b in the first embodiment. The pattern projection plate 41 shields the irradiation light so as to form a concentric stripe pattern, and as shown in FIG. 7, for example, a transparent glass having a thickness of 1 mm. The plate is provided with a concentric pattern with a light-shielding coating as a shielding portion on the surface so as not to transmit the irradiation light from the light source 11a, and a portion that is not coated with the light-transmitting portion. In the example shown in FIG. 7, the light transmission part has a concentric slit shape with a width of 1 mm, and is arranged so that the distance between adjacent ones is 1 mm. Thereby, the pattern projection apparatus 11 can project a concentric bright and dark pattern on the surface 14 to be measured.

  The photoelectric conversion element 12 in the present embodiment uses a CCD array in which light receiving elements are two-dimensionally arranged. Note that axes a to d in FIG. 7 correspond to pixel columns 1 to 4 to be described later of the photoelectric conversion element 12. Since the configuration of other points is the same as that of the first embodiment, description thereof is omitted.

  Next, the operation of the surface smoothness measuring apparatus in the present embodiment will be described.

  FIG. 8 is a diagram schematically showing the arrangement of the light receiving elements of the photoelectric conversion element in the second embodiment of the present invention.

  First, when light is applied to the surface 14 to be measured using the concentric pattern projection plate 41, concentric light images are similarly incident on the image receiving surface of the photoelectric conversion element 12. In the present embodiment, since the photoelectric conversion element 12 uses a CCD array in which light receiving elements are two-dimensionally arranged, a plurality of pixels as light receiving elements are two-dimensionally arranged on the image receiving surface. In FIG. 8, for the sake of explanation, the pixel array on the image receiving surface of the photoelectric conversion element 12 is represented by 25 pixels × 25 pixels, but actually, the image receiving surface of the photoelectric conversion element 12 has 1000 pixels × 25 pixels. About 1000 pixels are arranged.

  In the example shown in FIG. 8, the horizontal coordinate axis in the drawing is the x axis, the vertical coordinate axis is the y axis, and the center is the origin (x = 0, y = 0). Further, a pixel column existing on the y-axis, that is, a line of x = 0 is defined as a pixel column 1, a pixel column existing on the x-axis, that is, a line of y = 0 is defined as a pixel column 2, A column of pixels existing on the straight line y = x is referred to as a pixel column 3, and a column of pixels existing on the straight line y = −x is referred to as a pixel column 4. The angle between adjacent ones of the pixel columns 1 to 4 is 45 degrees. In the present embodiment, the smoothing described in the first embodiment is performed on the four pixel columns of the pixel column 1 to the pixel column 4 based on the received light intensity distribution for each pixel column. The degree (S) is obtained according to the equation (3).

  Here, the anisotropy of the shape of the measurement object surface 14 and the reflection of light will be described.

  FIG. 9 is a diagram showing light reflection by the surface of the object to be measured in the second embodiment of the present invention, and FIG. 10 is a diagram showing a received light intensity distribution waveform for each pixel column in the second embodiment of the present invention. It is. In FIG. 9, for convenience of explanation, the horizontal direction in the drawing is X, the vertical direction is Z, and the normal direction is Y.

  The surface 14 to be measured has the shape shown in FIG. 9, and the shape is the same regardless of the value of Y. This assumes that the surface 14 to be measured is a surface having irregularities on the streaks in a certain direction, such as a grinding trace of a metal surface. In the case of such a surface shape, scattering of reflected light occurs strongly in the plane of FIG. 9 (in the XZ plane) and hardly scatters in the normal direction (Y direction) of the paper. But it can be considered very weak.

  When the surface 14 to be measured having such anisotropy is measured by the surface smoothness measuring apparatus in the present embodiment, the pixel rows 1 shown in FIG. 8 are arranged on the XZ plane of FIG. In this case, since the received light intensity distributions of the four pixel columns 1 to 4 having an angle of 45 degrees are measured, an intensity distribution waveform as shown in FIG. 10 is obtained. 10A shows the intensity distribution waveform of the pixel column 1, FIG. 10B shows the intensity distribution waveform of the pixel column 2, FIG. 10C shows the intensity distribution waveform of the pixel column 3, FIG. 10D shows the intensity distribution waveform of the pixel column 4.

  From FIG. 10, it can be seen that the smoothness of the pixel row 1 is high, the smoothness of the pixel row 2 is low, and the pixel row 3 and the pixel row 4 show intermediate smoothness.

  As described above, in the present embodiment, the concentric pattern projection plate 41 is used, and the smoothness of each is obtained based on the intensity distribution waveforms of a plurality of pixel columns having an angle of 45 degrees with each other. ing. Therefore, in addition to the effects of the first embodiment, it becomes possible to detect the anisotropy of the surface shape of the measurement object surface 14 and to measure the state of the measurement object surface 14 in more detail. .

  In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.

It is the schematic of the surface smoothness measuring apparatus in the 1st Embodiment of this invention. It is a figure which shows the pattern projection board in the 1st Embodiment of this invention. It is a block diagram which shows the structure of the signal processing apparatus in the 1st Embodiment of this invention. It is a figure which shows the relationship between the surface smoothness of the to-be-measured object surface in the 1st Embodiment of this invention, and the output of a photoelectric conversion element. It is a figure which shows the numerical formula which calculates the average of the A / D-converted data in the 1st Embodiment of this invention, and the average of the maximum value or minimum value of a signal waveform, and the value of smoothness. It is a figure which shows the light reception intensity distribution waveform about two to-be-measured object surfaces from which the reflectance in the 1st Embodiment of this invention differs. It is a figure which shows the pattern projection board in the 2nd Embodiment of this invention. It is a figure which shows typically the arrangement | sequence of the light receiving element of the photoelectric conversion element in the 2nd Embodiment of this invention. It is a figure which shows reflection of the light by the to-be-measured object surface in the 2nd Embodiment of this invention. It is a figure which shows the light reception intensity distribution waveform about each pixel row | line in the 2nd Embodiment of this invention.

Explanation of symbols

11a Light source 11b, 41 Pattern projection plate 12 Photoelectric conversion element 13 Signal processing device 14 Measurement object surface 23 Data analysis unit 31 Opening

Claims (3)

(A) a light source for irradiating the object surface with light;
(B) a light-shielding unit that is provided between the object and the light source, and shields the irradiation light applied to the object from the light source so as to form a specific pattern composed of brightness and darkness in a predetermined direction;
(C) light receiving means for receiving reflected light reflected from the object surface;
(D) a received light intensity distribution detecting means for detecting a received light intensity distribution for each position in a predetermined direction based on the light received by the light receiving means;
(E) having a smoothness calculating means for calculating the smoothness of the object surface based on the received light intensity distribution detected by the received light intensity distribution detecting means;
(F) The light-shielding means includes a light-shielding part that shields light and a light-transmissive part that transmits light, and the light-transmissive parts are arranged concentrically alternately at predetermined intervals, and the irradiation light is concentrically shaped. Shield to form a striped pattern,
( G ) The surface smoothness measuring apparatus, wherein the smoothness calculating means calculates smoothness in a plurality of directions based on a maximum value and a minimum value obtained from a light reception intensity distribution in a plurality of directions. 2. The surface smoothing according to claim 1, wherein the smoothness calculating means calculates an average value Max (Ave) of the maximum value and an average value Min (Ave) of the minimum value, and calculates the smoothness by the following formula. Sex measuring device.
Smoothness = (Max (Ave) −Min (Ave)) / (Max (Ave) + Min (Ave)) The surface smoothness measuring apparatus according to claim 1 or 2 , wherein the plurality of directions are four directions, and an angle between adjacent directions is 45 degrees.

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