JP2007147324A - Surface inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface inspection device capable of inspecting a defect having a fine size on an inspection object surface, and hardly affected by roughness, dirt or the like on the surface. <P>SOLUTION: In this surface inspection device 1 wherein reflected light of light floodlighted from a light source 24 onto the inner surface of the inspection object through a floodlighting fiber 20 is received through light receiving fibers 21, and a two-dimensional image corresponding to the surface of the inspection object 2 is generated based on the light receiving quantity, a plurality of light receiving fibers 21 are arranged around the floodlighting fiber 20, and the diameter of each light receiving fiber 21 is set to be larger than the diameter of the floodlighting fiber 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface inspection apparatus for inspecting foreign matter, fine grooves or scratches present on the surface of an object to be inspected.

As a device that can inspect grooves and scratches on the surface of the object to be inspected, the reflected light of the light projected from the light source to the surface of the object to be inspected via the light projecting fiber is received via the light receiving fiber. A surface inspection apparatus that generates a two-dimensional image corresponding to the surface of an object to be inspected based on the amount of received light and detects grooves and scratches on the surface is known. This apparatus also includes a rotating means for rotating the light projected through the light projecting fiber along the inner periphery of the cylindrical body and a linear moving means for moving the light along the axial direction of the cylindrical body. The inner surface of the body can also be inspected (for example, see Patent Document 1).
JP-A-11-281582

  In order to detect fine grooves and scratches with this surface inspection apparatus, it is necessary to make the light emitting fiber thinner to reduce the light irradiation spot and improve the resolution. However, if the irradiation spot is made smaller, it becomes more susceptible to light scattering due to surface roughness and dirt, and there arises a problem that it becomes difficult to distinguish the groove to be detected from these roughness and dirt. For this reason, it is difficult to use a conventional surface inspection apparatus for detecting fine grooves.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a surface inspection apparatus that is less susceptible to surface roughness and dirt, and that can inspect defects such as fine grooves on the surface of an object to be inspected.

  In the surface inspection apparatus of the present invention, the reflected light of the light (L) projected from the light source (24) onto the surface of the inspection object (2) via the light projecting fiber (20) is transmitted via the light receiving fiber (21). In the surface inspection apparatus (1) for inspecting the surface of the inspection object (2) based on the amount of received light, a plurality of the light receiving fibers (21) are arranged around the light projecting fiber (20). The above-mentioned problem is solved by making the diameter of the light receiving fiber (21) larger than the diameter of the light projecting fiber (20).

  As described above, in a surface inspection apparatus, if the light projecting fiber is made thinner in order to improve the resolution, the influence of light scattering due to roughness or dirt existing in a shallow portion of the surface increases on the reflected light. come. However, even in this case, the amount of regular reflection is large and the spread of scattered light from the light projection position is small as compared with the reflected light from the groove or scratched portion. In the surface inspection apparatus of the present invention, a plurality of light receiving fibers are arranged around the light projecting fiber and the diameter of the light receiving fiber is larger than that of the light projecting fiber, so that the light receiving area is wider than the conventional one. Therefore, in the case of the reflected light from a rough or dirty portion having a large amount of regular reflection and a relatively narrow spread of scattered light, it is possible to pick up a considerable proportion of the reflected light from the entire reflected light. On the other hand, the scattered light from the grooves and scratches on the surface has less specularly reflected light and the scattered light is greatly spread. Therefore, even if the light receiving area is increased, the surface is rough or dirty. The rate of increase in the amount of received light is small. That is, according to the surface inspection apparatus of the present invention, it is possible to greatly increase only the amount of light received from the rough or dirty portion without increasing the amount of light received from the groove or scratched portion. Therefore, it is possible to clearly distinguish a portion where roughness or dirt is present from a portion where grooves or scratches are present.

  Moreover, in one form of this invention, you may provide the nonlinear amplification means (4) which photoelectrically converts the light received with the said light reception fiber (21), and amplifies the signal after photoelectric conversion nonlinearly. As described above, by increasing the light receiving area, it is possible to distinguish the groove and the scratched portion from the rough surface and dirt even if the resolution is improved. However, even in that case, the higher the resolution, the more the output signal corresponding to the light received from the groove and scratched part after photoelectric conversion and the light received from the rough surface and dirt part. The boundary with the corresponding output signal is present in a portion where the signal intensity is lower than the output signal corresponding to the light received from the portion having a smooth surface and no contamination. Therefore, if the signal after photoelectric return is amplified non-linearly so that it is greatly amplified in the low range of the output signal as in this embodiment, it is easier to distinguish surface grooves and scratches from surface roughness and dirt. It becomes possible to do.

  The signal after the photoelectric conversion is a voltage signal, and the amplification factor of the nonlinear amplifying means (4) can be increased in the low voltage portion and decreased in the high voltage portion. In addition, a log amplifier can be provided as the nonlinear amplifying means. According to this, as described above, if the voltage signal after photoelectric return is amplified non-linearly so that it is greatly amplified in the low voltage portion where the output voltage is low, surface grooves and scratches and surface roughness and dirt can be further increased. It becomes possible to distinguish easily.

  Rotating means (12) for rotating the light projected from the light projecting fiber (20) along the inner periphery of the cylindrical body (2), wherein the object to be inspected is an inner surface of the cylindrical body (2). The linear movement means (13) that moves along the axial direction of the cylindrical body (2), the clock signal generation means (5) that generates a clock signal corresponding to the rotation of the rotation means (12), and the amplified signal. A / D conversion means (6) for A / D converting the electrical signal in synchronism with the clock signal. According to this, since the amplified electrical signal is A / D converted based on the clock signal from the signal generating means, the two-dimensional image is not easily affected by the rotation unevenness.

  The inspection object is a cylinder head of an engine, the surface of the inspection object is an inner surface of the cylinder head, and the grooves and scratches are fitted into the side surfaces of the recesses provided in the inner surface and the valve seats. It is good also as a clearance gap with the side surface. According to this, it becomes possible to inspect minute grooves and scratches on the inner surface of the cylinder head of the engine without being affected by surface roughness or dirt.

  In addition, in the above description, in order to make an understanding of this invention easy, the reference sign of the accompanying drawing was attached in parenthesis, but this invention is not limited to the form of illustration by it.

  As described above, according to the surface inspection apparatus of the present invention, it is possible to clarify the difference between fine grooves and scratches on the surface and surface roughness and dirt, and it is possible to detect the grooves and scratches clearly. Therefore, for example, it can be incorporated into a production line with strict inspection standards for automobile parts and the like, and can be used for detection of fine defects, and product accuracy and throughput can be improved.

  FIG. 1 is a schematic view of one embodiment of the surface inspection apparatus of the present invention. In the present embodiment, a surface inspection apparatus for inspecting the inner surface of a cylindrical body as an inspection object will be described below. However, the present invention is not limited to this, and the surface of a planar inspection object is inspected. May be. As shown in the drawing, a surface inspection apparatus 1 according to the present invention is inserted into a cylindrical body 2 that is an object to be inspected, and inspects a light receiving the reflected light while projecting light L on the inner surface of the cylindrical body 2. Then, the nonlinear amplifier 4 which is nonlinear amplifier means for nonlinearly amplifying the received light and the signal sent from the nonlinear amplification section 4 are A / D converted by the sampling clock signal from the encoder 5 which is clock signal generation means. An A / D converter 6 that is an A / D conversion means, a control unit 7 that performs various controls on the inspection unit 3 and the A / D converter 6, and an arithmetic processing unit that performs these various types of control and other processes to be described later 8.

  FIG. 2 is a diagram showing a schematic configuration of the inspection unit 3. As illustrated, the inspection unit 3 includes a laser diode (hereinafter referred to as LD) 24 that is a light source, and a photodetector (hereinafter referred to as PD) that photoelectrically converts received light to generate a voltage corresponding to the amount of received light. 25), the sensor head 10 that transmits light from the LD 24 to the PD 25, the outer cylinder 11 that surrounds the outside of the sensor head 10, the rotating mechanism 12 that is a rotating means that rotates the outer cylinder 11, and the outer cylinder 11. A linear movement mechanism 13 that is a linear movement means that moves forward and backward; an encoder 5 that generates a sampling clock signal in accordance with rotation; and a sensor head adjustment mechanism 14 that moves the sensor head 10 to focus light. .

  The sensor head 10 is attached to a light projecting fiber 20 and a light receiving fiber 21, a holding tube 22 that holds the light projecting fiber 20 and the plurality of light receiving fibers 21, and a tip of the holding tube 22. And a convex lens 23 that condenses light to the outside and condenses light from the outside to the inside. The base end of the light projecting fiber 20 is connected to the LD 24, and the base end of the light receiving fiber 20 is connected to the PD 25. The light generated by the LD 24 is projected onto the convex lens 23 through the light projecting fiber 20, and the light incident from the convex lens 23 is transmitted to the PD 25 through the light receiving fiber 21.

  FIG. 3A shows a cross-sectional view of the light projecting fiber 20 and the light receiving fiber 21 in the holding cylinder 22. As shown in the drawing, four light receiving fibers 21 are arranged around one light projecting fiber 20, and the diameter of the light receiving fiber 21 is larger than the diameter of the light projecting fiber 20. Large light receiving area. Note that the number of light receiving fibers arranged around the light projecting fiber is not limited to four, and may be any number, for example, three as shown in FIG. 3B. It is also possible to arrange a light receiving fiber.

  Returning to FIG. 2, the outer cylinder 11 that covers the outside of the sensor head 10 is disposed coaxially with the sensor head 10, and a light projecting / receiving portion 30 for allowing light to pass through is opened at the side of the tip. Further, a reflecting mirror 31 is attached to the distal end portion inside the outer cylinder 11 at an angle of 45 degrees with respect to the axis C of the outer cylinder 11. By this reflecting mirror 31, the light passing through the convex lens 23 of the sensor head 10 is bent at a right angle and is projected through the light projecting / receiving unit 30 onto the inspection region R on the inner surface of the cylindrical body 2. The reflected light from the inspection region R is also bent at a right angle by the reflecting mirror 31 through the light projecting / receiving unit 30 and transmitted to the light receiving fiber 21 through the convex lens 23.

  On the other hand, the rotation mechanism 12 attached to the base end side of the outer cylinder 11 includes a rotation motor. When the outer cylinder 11 is rotated by the rotation mechanism 12, the reflecting mirror 31 fixed to the outer cylinder 11 is also provided. Together, the position of the inspection region R rotates along the circumferential direction of the inner surface of the cylindrical body 2. When the outer cylinder 11 makes one rotation, the inspection region R makes a round on the inner surface of the cylindrical body 2 and a sampling clock signal is generated from the encoder 5 in accordance with the rotation.

  In addition, a linear movement mechanism 13 such as a linear motor is attached to the inspection unit 3 so that the outer cylinder 11 can move forward and backward along the axial direction C of the cylindrical body 2. Thereby, the light from the light projecting / receiving unit 30 scans the inner surface of the cylindrical body 2 along the circumferential direction and relatively moves in the axial direction, so that the entire inner surface of the cylindrical body 2 can be inspected over a wide range. it can.

  Returning to FIG. 1, the light transmitted from the light receiving fiber 21 is photoelectrically converted by the PD 25 and converted into a voltage corresponding to the amount of light received. The non-linear amplifier 4 connected to the PD 25 amplifies the voltage from the PD 25 non-linearly, and has a log amplifier (not shown), where the low voltage portion is greatly amplified, The high part is amplified small.

  Note that a fast Fourier transform device, a low-pass filter, and an inverse Fourier transform device can be arranged next to the nonlinear amplifier 4. Alternatively, only the low-pass filter can be arranged next to the nonlinear amplifier 4. According to this, it is possible to eliminate the influence of light scattering due to surface roughness and dirt that often appear in the high frequency region, and the influence of other noises. For example, when a fast Fourier transform device, a low-pass filter, and an inverse Fourier transform device are arranged, if the inspection time of one round is 20 ms, 0.2 ms, which is 1/100, and a frequency of 5000 Hz or more is cut by the low-pass filter. It is effective.

  The non-linear amplifier 4 is connected to the A / D converter 6 directly or via a fast Fourier transform device, a low-pass filter and an inverse Fourier transform device, or a low-pass filter. 5 is sampled and A / D converted in accordance with a sampling clock generated from 5. The sampled digital signal is recorded in a storage device of the arithmetic processing unit 8 described later via the control unit 7. The control unit 7 also controls the LD 24, the rotation mechanism 12, the linear movement mechanism 13, and the sensor head adjustment mechanism 14.

  FIG. 4 shows a configuration diagram of the arithmetic processing unit 8 connected to the control unit 7. As illustrated, the arithmetic processing unit 8 includes an arithmetic device 40, a keyboard 41a and a mouse 41b as input devices 41 for the arithmetic device 40, and a monitor 42a and a printer 42b as output devices 42 as necessary. ing. The arithmetic device 40 can be, for example, a personal computer including a computer unit including a microprocessor and peripheral devices such as a storage device 43 (RAM and ROM) necessary for the operation thereof.

  The arithmetic unit 40 performs sampling in accordance with the rotational movement as described above on a two-dimensional plane in which the circumferential position of the inner surface of the cylindrical body 2 is the x coordinate and the longitudinal position of the inner surface of the cylindrical body 2 is the y coordinate. The display control means 44 further represents a digital signal corresponding to the received light amount stored in the storage device 43 as the intensity of the luminance of the pixel. Further, an image processing means 45 for binarizing and edge processing the displayed two-dimensional image is also provided.

  Further, the arithmetic device 40 includes a groove width determining means 46 for obtaining the width of the groove provided on the inner surface of the cylindrical body 2. The groove width determination means 46 binarizes a two-dimensional image in which the amount of received light is represented by the luminance intensity of the pixel, further divides the image obtained by edge processing into a plurality of lines along a straight line extending in the y direction, The groove width is determined for each divided section. In this embodiment, the edge-processed image is divided. However, the present invention is not limited to this, and a two-dimensional image in which the amount of received light is expressed by its intensity or a binarized image may be divided.

  FIG. 5 is a flowchart showing an algorithm in which the groove width determining means 46 determines the groove width for each divided section. In this flowchart, first, in step 1, the two-dimensional image plane is divided into a plurality along a straight line extending in the y direction based on an instruction such as the number of divisions input by the operator from the input device 41. In step 2, the x-axis coordinate is fixed at one point in one divided section, and moves from one of the grooves to the groove along the y-axis, and the luminance of the pixel changes between adjacent pixels exceeding a specific threshold value. One point to be searched is retrieved, and the y coordinate at that time is stored as the y coordinate corresponding to one side edge of the groove. In step 3, on the same x-axis coordinate, the other point moves from the other side of the groove along the y-axis toward the groove, and the luminance of the pixel corresponding to the amount of received light changes beyond a certain threshold value between adjacent pixels. And the y coordinate at that time is stored as the y coordinate corresponding to the other side edge of the groove. In step 4, it is examined whether the y-coordinates of both side edges are obtained by the number of x-coordinates set in advance by the operator and to be searched in one divided section. If the predetermined number has not yet been obtained, the process proceeds to step 5 where the x coordinate is moved within the same divided section and the process returns to step 2 again. Then, the operation from step 2 to step 4 is repeated. When the y-coordinates of both side edges are obtained for a predetermined number of x-coordinates, the process proceeds to the next step 6. In step 6, the y-coordinates of the plurality of one side edges stored in step 2 are totaled, and the y-coordinate having the largest total number is set as the representative coordinates of the one side edge. In step 7, similarly, the y-coordinates of the plurality of other side edges stored in step 3 are totalized, and the representative coordinates of the other side edge of the y-coordinate having the largest number of totals are obtained. In step 8, the difference between the representative coordinates of the one side edge and the representative coordinates of the other side edge is obtained, and the difference is stored as the representative groove width in the divided section. In step 9, it is examined whether representative groove widths have been determined for all the divided sections. If not determined for all the divided sections, the divided sections are moved in step 10 and the process returns to step 2 again. Do. When the representative groove width is determined for all the divided sections, the flowchart ends. The calculation result is appropriately output from an output device such as a monitor.

  Next, in the surface inspection apparatus of the present embodiment, the width of the gap between the side surface of the recess formed on the inner surface of the cylinder head of the engine of the automobile and the side surface of the ring-shaped valve seat attached to the recess is inspected, A case where the width is measured will be described.

  FIG. 6A is a schematic view of a cylinder head of an automobile engine. The cylinder head 2 of the engine is usually manufactured from an aluminum alloy or the like, and is formed with an intake port 101 for supplying intake air into the combustion chamber and an exhaust port 102 for discharging exhaust gas after combustion. Yes. Each port 101, 102 is opened and closed by a valve 103, and a recess 104 is provided at the tip of each port 101, 102. The recess 104 has a valve airtightness and durability. In order to ensure this, a ring-shaped valve seat 105 made of an iron-based sintered material or the like is fitted. Although it is desirable that the valve seat 105 and the recess 104 are fitted with no gap, a slight gap G is actually generated due to a manufacturing error or the like. When the gap G becomes large, desired engine performance cannot be obtained. Therefore, it is necessary to accurately measure the width of the gap G and eliminate defective products having a gap of a certain value or more. Such a gap G exists on the inner surface of the cylinder head 2 as shown in the figure and cannot be directly observed. For this reason, conventionally, a method is widely used in which an operator manually inserts a shim made of a thin plate material into the gap G, and if the shim enters, the gap G having that thickness exists. However, this method has a great influence on the skill level of the worker, lacks objectivity, and is a manual operation, so that it is difficult to inspect all products.

  Inspection of the width between the side surface of the recess formed on the inner surface of the cylinder head 2 and the side surface of the ring-shaped valve seat 105 attached to the recess by the surface inspection device of this embodiment and determination of the width Is performed as follows. First, in a state where the valve 103 is not attached, the axis line of the cylinder head 2 and the axis line C of the outer cylinder 11 are made to coincide with each other in the port where the intake port 101 or the exhaust port 102 is inspected. The outer cylinder 11 of the surface inspection apparatus 1 is arranged so that the portion 30 comes to the position 105 of the valve seat. FIG. 6B shows the case where the surface inspection apparatus 1 is inserted into the intake port 101. Next, the sensor head 10 is moved by the sensor head adjustment mechanism 14 shown in FIG. 2, and the light L is focused on the inner surface of the cylinder head 2. As a result, the light from the LD 24 passes through the light projecting fiber 20, is collected by the convex lens 23, reaches the reflecting mirror 31, the optical path is changed at a right angle, and the light from the light projecting / receiving unit 30 to the inner surface of the valve seat 105. The light is projected onto the inspection region R.

  When the rotation mechanism 12 and the linear movement mechanism 13 are driven in this state, light from the light projecting fiber 20 is sequentially projected onto the inner surface of the cylinder head 2, and reflected light is received by the light receiving fiber 21 from the entire circumference of the inner surface. Is done. Then, the outer cylinder 11 rotates and advances in the axial direction C, and an inspection within a predetermined range from the inner surface of the valve seat 105 to the inner surface of the cylinder head 2 becomes possible.

  The reflected light L passes through the light projecting / receiving unit 30, is bent at a right angle by the reflecting mirror 31, collected by the convex lens 23, and received by the light receiving fiber 21. In this case, since the surface of the cylinder head 2 is relatively smooth, most of the light projected from the light projecting fiber 20 is regularly reflected and received by the light receiving fiber 21. Since the surface of the valve seat 105 is rougher than the inner surface of the cylinder head 2, if the projection fiber 20 is thinned to reduce the irradiation spot diameter, the influence of light scattering appears. In the groove G portion, light scattering is larger than that in the bulb seat 105 portion, and there is almost no regular reflection of light.

  Here, the light receiving area is expanded by arranging four light receiving fibers 21 around the light projecting fiber 20 and making the diameter of the light receiving fiber 21 larger than that of the light projecting fiber 20. For this reason, the amount of light received by the light receiving fiber 21 from the portion of the valve seat 105 increases, while the amount of light received from the portion of the groove does not increase so much. Therefore, the difference between the surface portion of the valve seat and the groove portion becomes clear.

  Next, while the inner surface of the cylinder head 2 is scanned spirally, the above-mentioned signal obtained via the light receiving fiber 21 is photoelectrically converted by the PD 25 to be converted into a voltage corresponding to the amount of received light, and is amplified by the nonlinear amplifier 4. . FIG. 7 is a graph showing the relationship between the signal input to the nonlinear amplifier 4 from the PD 25 and the output voltage after nonlinear amplification by the log amplifier of the nonlinear amplifier 4. The portion indicated by A in FIG. 7 is a signal portion from the PD 25 in the groove portion. On the other hand, a portion indicated by B in FIG. 7 is a signal portion other than the groove portion including a signal from the PD 25 of the valve seat portion. Here, the signal portion A from the groove in the input signal from the PD 25 and the other signal portion B have a certain difference by increasing the light receiving area of the light receiving fiber 21 as described above. Furthermore, if this difference can be enlarged, both can be more clearly distinguished. On the other hand, the difference portion exists at a position where the signal is small in the entire input signal. Therefore, by amplifying the input signal from the PD logarithmically with a non-linear amplifier or log amplifier, this difference is enlarged, the difference in output voltage between the two becomes large, and grooves and scratches on the surface are removed. It becomes easier to distinguish from rough and dirty. In addition, when a fast Fourier transform device, a low-pass filter and an inverse Fourier transform device, or a low-pass filter are arranged after the log amplifier, the influence of light scattering due to surface roughness or dirt that often appears in the high-frequency region, The influence of noise is eliminated.

  This output voltage is sampled and A / D converted by the A / D converter 6 according to the sampling clock generated from the encoder 5. Then, the inner surface of the cylinder head 2 is developed by the display control means 44 of the arithmetic processing unit 8 by converting the cylinder head 2 into grid-like image data with the circumferential direction of the cylinder head 2 as the x axis and the axial direction as the y axis. Such a two-dimensional image can be obtained. Here, since the sampling clock signal is directly generated from the encoder attached to the rotation mechanism, the rotation of the light and the received light data can be synchronized, and the two-dimensional image is hardly affected by the rotation unevenness.

  FIG. 8 is a two-dimensional image obtained by inspecting the portion of the inner surface of the air cylinder where the valve seat is attached with the surface inspection apparatus 1 of the present invention. In the figure, A is the inner surface of the cylinder head 2, and since the surface is relatively smooth, the amount of reflected light is large and white. Further, B in the figure is the inner surface of the valve seat 105, and since this portion is rougher than the inner surface of the cylinder head 2, the amount of reflected light is small and blackish. In the drawing, G is a gap between the cylinder head 2 and the valve seat 105, and since there is almost no reflected light from this portion, it is black. Although not shown, in the case of a conventional surface inspection apparatus in which the number of light receiving fibers is not plural and the amplifier is linear, the inner surface of the cylinder head 2 is pure white in the same two-dimensional image, and the valve seat 105 and the groove Both parts are completely black and cannot be distinguished from each other. However, according to the surface inspection apparatus of the present embodiment, as shown in FIG. 8, there is a difference in brightness between the valve seat portion B and the groove portion G, and it is possible to distinguish between the two. Become.

  In order to specify the groove G more clearly, the brightness of the pixel in the image of FIG. 8 is calculated, a threshold is set between the brightness of the groove G and the brightness of the valve seat B, and the brightness of the pixel If the threshold value is equal to or greater than the threshold value, white is set for the pixel, and if the threshold value is equal to or less than the threshold value, binarization processing is performed for setting the pixel to black. An image obtained by this processing is shown in FIG. 9, and the groove G can be clearly identified. Further, the image is edge-processed, and one side edge g1 and the other side edge g2 of the groove G are displayed with black dots as shown in FIG. The binarization process and the edge process are optional, and the coordinates of the edge of the groove G can be obtained directly from the data shown in FIG. 5 without performing these processes.

  Next, this image is equally divided into sections 1 to 10 along the x-axis as shown in FIG. 10 (S1). Then, in the first section Z, the x coordinate is fixed to one point, and along the y coordinate, a black point corresponding to the one side edge portion g1 is searched from the position of the y coordinate a in the figure toward the groove. Is obtained and stored (S2). Next, a black point corresponding to the other side edge portion g2 is searched from the position of the y coordinate b in the figure toward the groove, and the y coordinate of the point is obtained and stored (S2). In this case, although there are points on the y coordinate that do not correspond to the edge of the groove due to the influence of noise or the like, they are appropriately excluded.

  Then, in the first section Z, the y coordinate of a predetermined number of both side edges is obtained (S4, S5), and the coordinates occupied by the most points among the searched y coordinates of one point are set as one side edge. (S6). Similarly, the representative coordinates of the other side edge of the coordinates occupied by the most points among the y coordinates of a plurality of other points searched are used (S7). Next, the difference between the representative coordinates of the one side edge and the representative coordinates of the other side edge is obtained, and the value is set as the representative groove width of the first section (S8). Further, the same calculation is performed for the second section to the tenth section and the first section (S9, S10), and the representative width for each section is obtained. As described above, according to the groove width determining means 46 of this embodiment, the representative width for each section of the groove G can be determined automatically and objectively.

  The groove width may not be constant, for example, when the valve seat is inclined. In this case, if the groove width is calculated in the entire circumferential direction, an average value is obtained. However, in the case of a valve seat, the maximum groove width may be more problematic than the average value. According to the present embodiment, since the calculation is performed by dividing into a plurality of equally spaced regions, when the groove width is not constant, the groove width can be obtained for each divided section, and the maximum groove width and the minimum groove width can also be obtained. it can. It can also be determined whether or not the valve is tilted. However, the present embodiment is not limited to this, and it is possible to determine a representative groove width for the whole without dividing, and it is also possible to obtain only the groove width at one point of the groove.

  As described above, according to the surface inspection apparatus 2 of the present embodiment, since the light receiving area of the light receiving fiber 21 is expanded and the nonlinear amplifier is provided, a fine gap between the side surface of the cylinder head of the engine and the side surface of the valve seat, It is possible to clarify the difference between the surface and the roughness of the valve seat surface, and to detect the minute gap clearly. Therefore, the surface inspection apparatus of this embodiment can be incorporated into a production line with strict inspection standards for automobile parts, etc., and all products can be inspected, and product accuracy, quality and throughput can be improved.

  In addition, although the suitable form of this invention was demonstrated, this invention may be implemented with a various form, without being limited to the form mentioned above. For example, as described above, in the present embodiment, the surface inspection apparatus that inspects the inner surface of the cylindrical body as the object to be inspected has been described. However, the present invention is not limited thereto, and the surface inspection apparatus inspects the surface of the planar object to be inspected. May be.

Schematic of one form of the surface inspection apparatus of this invention. The figure which showed the block diagram of one form of a test | inspection part. Sectional drawing of a light projecting fiber and a light receiving fiber. The block diagram of the arithmetic unit of the surface inspection apparatus of this invention. The flowchart which showed the algorithm which determines a groove width for every division | segmentation area. Schematic of a cylinder head of an automobile. The graph which showed the nonlinear amplification in a nonlinear amplifier. The two-dimensional image which test | inspected the clearance gap between the inner peripheral recessed part and valve seat of an engine cylinder with the surface inspection apparatus of this invention. The image which binarized the image of FIG. An image obtained by dividing the image of FIG. 9 by edge processing.

Explanation of symbols

1 Surface inspection device 2 Inspected object (cylindrical body, cylinder head)
4 Non-linear amplifier (non-linear amplification means)
5 Encoder (clock signal generation means)
6 A / D converter 12 Rotating mechanism (rotating means)
13 Linear movement mechanism (linear movement means)
20 Emitting fiber 21 Receiving fiber 30 Emitting / receiving section 46 Groove width determining means C Axis G Groove L Light g1 One point g2 Other point

Claims (6)

In a surface inspection apparatus that receives reflected light of a light projected from a light source through a projection fiber onto a surface of the inspection object through a light receiving fiber and inspects the surface of the inspection object based on the amount of the received light ,
A surface inspection apparatus in which a plurality of the light receiving fibers are arranged around the light projecting fiber, and a diameter of the light receiving fiber is larger than a diameter of the light projecting fiber.   The surface inspection apparatus according to claim 1, further comprising: a nonlinear amplifying unit that photoelectrically converts light received by the light receiving fiber and nonlinearly amplifies the electric signal after the photoelectric conversion.   3. The surface inspection apparatus according to claim 2, wherein the signal after the photoelectric conversion is a voltage signal, and the amplification factor of the non-linear amplification means is large in the low voltage part and small in the high voltage part.   The surface inspection apparatus according to claim 3, wherein a log amplifier is provided as the nonlinear amplification means.   The surface of the object to be inspected is an inner surface of a cylindrical body, rotating means for rotating light projected through the light projecting fiber along the inner circumference of the cylindrical body, and an axial direction of the cylindrical body Linear moving means for moving along the clock, clock signal generating means for generating a clock signal corresponding to the rotation of the rotating means, and A / D for A / D converting the amplified electrical signal in synchronization with the clock signal The surface inspection apparatus according to claim 2, further comprising conversion means. The object to be inspected is an engine cylinder head, and the surface of the object to be inspected is an inner surface of the cylinder head, and the grooves and scratches are fitted into the side surface of the recess provided on the inner surface and the recess. The surface inspection apparatus according to claim 1, wherein the surface inspection apparatus has a gap with a side surface of the valve seat.

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