JP5120625B2 - Inner surface measuring device - Google Patents

Description

  The present invention relates to an inner surface measuring apparatus including a slit light source that irradiates slit light and an imaging unit that images an inner surface of a measurement object irradiated with the slit light.

  Conventionally, for inspection of defects and shapes on the inner surface of a cylinder such as the inner surface of a cylinder, a conical reflector such as a cone mirror is inserted into the inspection site, and the reflector is moved up and down or rotated for a wide range of inspections. A method of visually inspecting a site is known. In visual inspection, variations in defect criteria and oversight occur due to the skill of the inspector. In addition, it is impossible to measure the shape of the inner surface by such visual observation, and a separate work process for measuring the shape is required.

  As a device for measuring the side or bottom surface of the object to be measured, at least one of a prism system for obtaining a side image for obtaining a side image of the object to be measured and a prism system for obtaining a bottom image for obtaining a bottom image is provided. There is a dimension measuring device using a multi-directional simultaneous observation optical system (for example, Patent Document 1). In this dimension measuring apparatus, the side surface image acquisition prism system and the bottom surface image acquisition prism system have an optical path direction changing prism function or an optical path direction changing prism function, and an optical path length correcting function. Each prism system is arranged so that the optical path of the light emitted by each prism is directed upward of the object to be measured, or parallel to and in the same direction as each other, and is not blocked by other prism systems. ing. The lens provided in the light output direction of the side surface image acquisition prism system and the bottom surface image acquisition prism system is a telecentric lens whose object side is telecentric, and based on the acquired image information, the measuring means measures the object to be detected. Measure the desired dimensions. In this dimension measuring device, it is devised to form a side image and a bottom image of the object to be measured on the imaging surface at the same time, but there is no contrivance regarding illumination on the object to be measured. For measurement inside a cylinder, etc., illumination light that reliably irradiates a measurement region at a deep position is required.

As a device for measuring the inside of an object to be measured using slit light as illumination light, the slit light irradiated from the slit light source is received by a slit light reflecting mirror that can be inserted into a cylinder to be measured such as a cylinder block. There is an internal dimension measurement device that irradiates a measurement site and images a measurement site irradiated with slit light by an imaging device through a reflecting mirror for an imaging device that can be inserted into a cylindrical body (for example, Patent Documents) 2). In this internal dimension measuring device, the irradiation optical axis of the slit light and the imaging optical axis of the imaging device are oriented so as to intersect. In addition, it is possible to perform pass / fail judgment by calculating a three-dimensional internal dimension from the image data acquired by the imaging device through a calculation based on a triangulation method.

Japanese Patent Laying-Open No. 2007-10447 (paragraph number 00001, FIG. 2) JP 2004-20340 (paragraph number 0004-0011, FIG. 1)

The internal dimension measuring device disclosed in Patent Document 2 is an effective device for measuring the inner surface of a cylinder or the like. There are disadvantages that the distance to the focal area is shortened, and measurement inside a deep cylinder is impossible. In addition, if a part with a distance difference exceeding the depth of field of the lens is scattered in the measurement area at one measurement point, measures such as accepting low measurement accuracy or measuring while shifting the measurement point Is required. Furthermore, when measuring the inner surface of a cylinder, depending on the angle between the optical axis of the slit light at the measurement point and the imaging optical axis, the specular reflection component of the slit light is incident on the imaging device at a specific curvature of the inner surface, and smear occurs. In addition, problems such as a decrease in measurement accuracy due to image shape expansion and measurement impossibility may occur.
In view of the above situation, an object of the present invention is to provide an inner surface measuring apparatus that can ensure a wide range of measurable inner surface conditions and obtain a more accurate measurement result when measuring the inner surface of an object to be measured using slit light. Is to provide.

Among the slit inner surface, the slit light source for irradiating the slit light, the imaging means for imaging the cylindrical inner surface of the measurement object irradiated with the slit light, the slit light deflecting means for deflecting the slit light to the cylindrical inner surface, An imaging prism that deflects the imaging optical axis of the imaging means to the slit light irradiation inner surface irradiated with the slit light, and the slit light source is irradiated with the slit light in a direction along the axial direction of the cylindrical inner surface The imaging means has a light receiving element that receives a light beam incident along the imaging optical axis, and the imaging optical axis is along the axial direction of the cylindrical inner surface. The slit light deflector disposed outside the cylindrical inner surface irradiates the slit light in the form of slit light extending in the axial direction of the cylindrical inner surface. Irradiating the surface, a slit which is emitted from the slit beam deflecting means such that the reflected light quantity of the slit light at said slit light irradiating the inner surface is minimized sensitivity amount or more and the saturation amount of the light receiving element in the entire measurement range The irradiation direction of light and the arrangement position of the imaging prism are adjusted, and the alignment at the inner surface of the slit light irradiation is made according to the irradiation angle of the slit light with respect to the inner surface of the slit light irradiation and the imaging angle of the imaging optical axis. In order to enlarge the focal range, the imaging surface of the light receiving element is inclined with respect to the imaging optical axis, and the imaging optical axis formed between the imaging prism and the slit light irradiation inner surface, the optical axis formed between the slit light deflecting means and said slit light irradiation inner surface, Ru are arranged on the same plane perpendicular to the axial direction of the cylindrical inner surface.

In the present invention, an imaging prism is used instead of a deflection mirror in order to deflect the imaging optical axis toward the slit light irradiation inner surface. Therefore, when this imaging prism is manufactured with a material having a refractive index exceeding 1.0, the optical path length is extended according to the length of the optical axis in the prism. Accordingly, even if the lens of the image pickup means alone has a short focal distance on the object side and cannot be incorporated, the optical path length is appropriately adjusted by using a material having an appropriate refractive index exceeding the refractive index of 1.0 as the material of the image pickup prism. The image pickup means can be incorporated. Therefore, the possibility of selecting a lens is widened.
Further, the irradiation direction of the slit light and the arrangement position of the imaging prism are adjusted so that the light amount is not less than the minimum sensitivity light amount of the light receiving element constituting the image pickup surface of the image pickup means and is within the saturated light amount. With this feature, the imaging unit can acquire a stable image, and as a result, measurement accuracy is improved.
Furthermore, due to the characteristic that the imaging surface of the imaging means is tilted with respect to the imaging optical axis, that is, by increasing the depth of field based on the principle of tilt shooting, a measurement range greater than the depth of field of the lens is secured. can do. This also contributes to highly accurate measurement.

The inner surface measuring apparatus according to the present invention may further include a cylindrical groove on the inner surface of the cylinder, and the imaging prism with respect to the irradiation direction of the slit light applied to the inner surface of the cylinder including the peripheral groove. Adjacent to the slit light deflecting means so as to be inside the specular reflection optical axis of the slit light that is disposed in the maximum circle corresponding to the bottom surface of the circumferential groove and the minimum circle corresponding to the opening surface of the circumferential groove. It is characterized by arranging. According to this feature, the slit light can be irradiated in the vertical direction to the measurement point on the inner surface where the slit light is to be measured by the slit light deflecting means. Further, by disposing the slit light deflecting unit and the imaging prism adjacent to each other, the possibility that the regular reflection component of the slit light of the slit light enters the imaging prism is reduced. In particular, when the measurement target is the inner surface of the cylinder, by adopting an arrangement in which the slit light deflecting unit and the imaging prism are adjacent to each other and decentered from the center of the cylinder toward the slit light deflecting unit side, the specular reflection component of the slit light is reduced. The possibility of entering the imaging prism is extremely reduced. As a result, a highly accurate measurement result can be obtained even if the inner surface conditions are strict, such as a cylindrical inner surface with a small inner diameter or an inner surface with a large measurement depth range.

  Embodiments of a cylinder inner surface inspection system incorporating an inner surface measuring apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view schematically showing a configuration of a cylindrical body inner surface inspection system according to the present embodiment. In this embodiment, the object to be inspected is a cylindrical body 10 having a peripheral wall formed with a circumferential groove having a cross section, and in particular, it is inspected whether or not foreign matter is mixed in the circumferential groove 11.

  The cylindrical inner surface inspection system includes an inner surface measuring device 1 and a controller 100 that performs control on the inner surface measuring device 1 and evaluates the measurement result. The inner surface measuring apparatus 1 includes a laser-type slit light source 2 that generates slit light, a slit light prism 3 as a slit light deflecting unit, an imaging prism 4, an imaging unit 5, and the like as main components of the measurement system. . In addition, the inner surface measuring apparatus 1 has an integrated frame 6 that integrally supports the components of the measurement system as main components of the mechanism system, and a rotational drive that rotates the integrated frame 6 around a vertical rotation axis. A mechanism 60, a vertical movement mechanism 61 that linearly moves the integrated frame 6 in the vertical direction, and the like are provided. Although not shown, an XY movement mechanism that changes the relative positional relationship on the XY plane between the cylindrical body 10 that is an inspection object and the integrated frame 6 is also provided.

  The slit light prism 3 makes the slit light emitted in the vertical direction from the slit light source 2 incident thereon, deflects it at a substantially right angle at the lower end portion thereof, and the inner peripheral surface (hereinafter referred to as the cylindrical body 10) having the end face placed below. , Simply referred to as the inner surface) in the form of slit light extending in the axial direction. Therefore, the optical cutting line S by the slit light extends in the axial direction of the cylindrical body 10 as can be understood from FIG.

The imaging prism 4 guides slit light reflected by the inner surface of the cylindrical body 10 to the imaging means 5. In other words, the imaging optical axis facing the vertical direction of the imaging unit 5 is deflected substantially at a right angle, and the imaging area including the light cutting line S is guided to the imaging unit 5 as an imaging field. The imaging prism 4 has a long shape in order to increase the passing distance of the photographing light in the photographing prism. Since this long shape and the imaging prism 4 are made of a material having a refractive index exceeding 1.0, the actual optical path length is extended, and the focal position of the imaging means 5 is determined by the imaging means 5. It is possible to match the inner surface of the cylindrical body 10 far away from the center. Similarly, the length and material of the slit light prism 3 are appropriately selected so that desired slit light can be applied to the inner surface of the cylindrical body 10.

  Here, the slit light prism 3 that irradiates slit light toward the measurement location and the imaging prism 4 that makes the reflected light of the slit light incident as imaging light are collectively referred to as a measurement head. Insert inside and measure inside.

  The imaging means 5 includes a lens unit 50 and an imaging unit 51 made up of a large number of light receiving elements (CCD and CMOS) arranged in a plane. The relationship between the imaging optical axis (slit optical axis of the slit light) of the imaging means 5 that images the inner surface (slit light irradiation inner surface) of the cylindrical body 10 irradiated with the slit light and the slit optical axis is schematically shown in a developed view. Is shown in FIG. The angle α formed by the slit light irradiation optical axis and the imaging optical axis is a narrow angle of 45 degrees or less. As can be understood from FIG. 2, when the difference in measurement depth (light propagation distance) along the slit optical axis direction exceeds the depth of field of the lens unit 50, an out-of-focus region occurs. In order to avoid this, the imaging surface 51a of the imaging unit 51 is tilted with respect to the imaging optical axis, and the depth of field is earned by the principle of tilt shooting. Thereby, a photographed image without blur can be acquired even in a measurement range that is greater than the depth of field of the lens unit 50.

  By arranging the slit light prism 3 and the imaging prism 4 close to each other, the angle α formed between the irradiation light axis of the slit light and the imaging optical axis is a narrow angle of 45 degrees or less. The adjacent arrangement of the slit light prism 3 and the imaging prism 4 is also effective in preventing the regular reflection light of the slit light from entering the photographing prism 4. As shown in FIG. 3, when imaging the inner surface of the cylindrical body 10 while irradiating the slit light, the irradiated slit light is reflected by the inner surface of the cylindrical body 10 and enters the imaging prism 4. At that time, since the regular reflection light has a strong light intensity, it is necessary to prevent the possibility that the regular reflection optical axis enters the imaging prism 4 and saturates the light receiving element of the imaging unit 51. For this purpose, the imaging prism 4 may be positioned inside the regular reflection optical axis. As shown in FIG. 3, since the range to be measured has a predetermined value, that is, the measurement point that generates the optical cross section line by the slit light has a fluctuation range in the irradiation direction of the slit light. Accordingly, the imaging prism 4 is disposed inside both the regular reflection optical axis at the innermost circle (measurement shortest distance) and the regular reflection optical axis at the maximum circle (longest measurement distance). Of course, the imaging prism 4 may be arranged outside both the regular reflection optical axis in the innermost circle and the regular reflection optical axis in the maximum circle. In this case, the imaging prism 4 and the slit light prism 3 may be arranged. Becomes larger and cannot be inserted into a cylindrical body having a small inner diameter. As can be understood from FIG. 3, by shifting the imaging prism 4 in a direction further away from the measurement point, it is possible to obtain more from both the regular reflection optical axis in the innermost circle and the regular reflection optical axis in the maximum circle. You can leave. For this reason, it is also preferable to make the measuring head made up of the imaging prism 4 and the slit light prism 3 slim by shifting the imaging prism 4 to the rear of the slit light prism 3 and adjacent to the slit light prism 3 as much as possible. is there. As the measuring head becomes slimmer, it can be inserted into the cylindrical body 10 having a small inner diameter and the inner surface thereof can be measured. As can be understood from FIG. 3, for the purpose of separating the specular reflection optical axis from the imaging prism 4, the measuring head composed of the imaging prism 4 and the slit light prism 3 so as to increase the reflection angle of the specular reflection optical axis. It is also preferable to place the lens toward the inner surface on the slit light prism 3 side.

  The controller 100 is substantially formed as a computer unit, and as related to the present invention, the light source control unit 80, the image memory 81, the image processing unit 82, the evaluation unit 83, the rotation drive control unit 84, the vertical movement A control unit 85 and an XY movement control unit 86 are provided. The XY movement control unit 86 controls the operation of an XY movement mechanism (not shown) to set the cylindrical body 10 that is a measurement object to an optimum position with respect to the inner surface measuring apparatus 1. The vertical movement control unit 85 controls the operation of the vertical movement mechanism 61 so that the measuring head composed of the imaging prism 4 and the slit light prism 3 comes from the home position to the inner surface position of the cylindrical body 10 to be measured. . The rotation drive control unit 84 controls the operation of the rotation drive mechanism 60 to rotate the measurement head set at the measurement height position 360 degrees around a vertical axis substantially equal to the axis of the cylindrical body 10. Thus, the measurement head can scan a specific measurement height region, for example, the region of the circumferential groove 11 over the entire circumference.

  The imaging unit 5 images the inner surface of the cylindrical body 10 irradiated with the slit light emitted from the slit light source 2 under the control of the light source control unit 80, that is, the light cutting line region. The image data sent from the imaging means 5 to the controller 100 is developed in the image memory. Furthermore, if necessary, the image processing unit 82 performs image processing such as coordinate conversion, level correction, and edge detection, and the light cutting line S by the slit light is detected. Since the evaluation unit 83 knows the irradiation point and irradiation angle of the slit light, and the angle formed by the slit optical axis and the imaging optical axis, the evaluation unit 83 is based on the triangulation method from the coordinate value of the light section line S detected by the image processing unit 82. The three-dimensional position of the light cutting line S, that is, the inner surface of the cylindrical body can be obtained. Instead of the calculation based on the triangulation method, a method using a table storing the calculation result may be employed. For example, when inspecting the circumferential groove 11 formed on the inner surface of the cylindrical body 10 as a measurement object as shown in FIG. 4, from the captured image data obtained by irradiating the circumferential groove 11 with slit light, A light section line S as shown in FIG. 5 which is a schematic display is detected. 5A is a detection form of the light cutting line S at a normal location, and FIG. 5B is a detection form of the light cutting line S at a location where a foreign object is present. By performing measurement scanning while rotating the measuring head 360 degrees, measurement of the circumferential groove 11 over the entire circumference is realized. A 360-degree unfolded inspection drawing can be created using the three-dimensional positions of all the light cutting lines S obtained by the entire circumference scanning. For example, FIG. 6 is a development inspection diagram in which the bottom surface of the circumferential groove 11 is used as a reference surface, and the distance in the depth direction is indicated by shading (reference surface is white). By comparing this inspection drawing with the shape dimension drawing of the inspection target area prepared in advance, it is possible to easily check for the presence of a foreign object, a dent, or the like.

The procedure for inspecting the circumferential groove 11 of the cylindrical body 10 using the cylindrical body inner surface inspection system configured as described above will be described below with reference to the flowchart shown in FIG.
Here, the inspection target is the cylindrical body 10, and the inspection target area is the circumferential groove 11 formed on the inner surface of the cylindrical body 10. First, the cylindrical body 10 is placed on a measuring table with an XY movement mechanism of the inner surface measuring apparatus 1 with its end face as a mounting surface (# 01). The X / Y movement control device 86 controls the X / Y movement mechanism, and the vertical movement control unit 85 controls the vertical movement mechanism 61 to insert the measurement head into the cylinder of the cylindrical body 10 so that the slit light is emitted from the circumferential groove 11. Is set as the measurement start position (# 02). The light source controller 80 controls the oscillation of the laser of the slit light source 2 and irradiates the slit light to the circumferential groove 11 via the slit light prism 3 to create the light cutting line S due to the luminance difference (# 03). The controller 100 develops the captured image acquired by the imaging unit 5 in the image memory 81 as image data using the measurement region of the circumferential groove 11 including the light cutting line S as the imaging region (# 04). The image processing unit 82 processes the image data and detects the light section line S (# 05). Based on the detected pixel position of the light cutting line S, the evaluation unit 83 calculates and stores the three-dimensional dimension (cross-sectional shape of the circumferential groove 11) (# 06). The rotation drive control unit 84 controls the rotation drive unit 60 to rotate the measurement head by a predetermined measurement angle pitch (# 07). It is checked whether or not the measurement of the circumferential groove 11 over the entire circumference is completed, that is, whether or not the measurement head has been rotated 360 degrees (# 08). If the measurement is not completed (# 08 No branch), the processing from step # 04 to # 07 is repeated for each measurement angle pitch. When the measurement is completed (# 08 Yes branch), the measurement head is returned to the home position to prepare for the next inspection (# 09). The evaluation unit 83 reads the stored three-dimensional dimension of the optical cutting line S ((cross section of the circumferential groove 11) over the entire circumference, for example, inspection surface shape data as schematically shown in FIG. Further, the shape data of the inspection surface is compared with the normal shape data to extract the shape of the defect (# 11), and then from the size of the extracted defect shape Then, the quality of the inspection object is determined (# 12).

  As described above, in the inner surface measuring apparatus 1 according to the present invention, slit light introduced from the slit light source 2 located outside the cylindrical body 10 through the slit light prism 3 inserted into the cylinder of the cylindrical body 10. Is used to irradiate the inner surface of the cylinder. Then, the irradiated inner surface is imaged by the imaging means 5 located outside the cylindrical body 10 by using imaging light introduced through the imaging prism 4 similarly inserted into the cylinder of the cylindrical body 10. . The acquired captured image data is processed by the controller 100, so that the calculation of the three-dimensional dimension of the inner surface shape of the cylindrical body 10 and the defect detection based on the calculated three-dimensional dimension are realized at high speed and with high accuracy.

The perspective view which shows typically the structure of the cylinder inner surface inspection system incorporating the inner surface measuring apparatus by this invention. Development view schematically showing the relationship between the slit optical axis and the imaging optical axis and the relationship between the imaging optical axis and the imaging surface. The top view explaining the relationship between the slit optical axis from the slit optical prism and the reflected optical axis toward the imaging prism Perspective view of cylindrical body with circumferential groove as inspection object Explanatory drawing which shows the optical cutting line in a circumferential groove 360 ° unfolded inspection drawing showing the cross-sectional shape of the circumferential groove in shades Flow chart showing the inspection procedure in the cylinder inner surface inspection system

Explanation of symbols

1: Inner surface measuring device 2: Slit light source 3: Slit light prism (slit light deflection means)
4: Imaging prism 5: Imaging means 50: Lens unit 51: Imaging unit 51a: Imaging surface 60: Rotation drive mechanism 82: Image processing unit 83: Evaluation unit 100: Controller

Claims (2)

A slit light source for irradiating slit light;
Imaging means for imaging the cylindrical inner surface of the object to be measured irradiated with the slit light;
Slit light deflecting means for deflecting the slit light toward the inner surface of the cylinder;
An imaging prism that deflects the imaging optical axis of the imaging means to the slit light irradiation inner surface irradiated with the slit light among the cylindrical inner surface ,
The slit light source is disposed outside the cylindrical inner surface so that slit light is irradiated in a direction along the axial direction of the cylindrical inner surface,
The imaging means has a light receiving element that receives a light beam incident along the imaging optical axis, and is disposed outside the cylindrical inner surface so that the imaging optical axis is along the axial direction of the cylindrical inner surface,
The slit light deflection unit irradiates the slit light irradiation inner surface with incident slit light in the form of slit light extending in the axial direction of the cylindrical inner surface,
The irradiation direction of the slit light amount of reflected light of the slit light at said slit light irradiating the inner surface is emitted from the slit beam deflecting means so that the light reception merit amount or more and the saturation amount of the element in the entire measurement range The arrangement position of the imaging prism is adjusted,
In order to expand the focusing range on the inner surface of the slit light irradiation according to the irradiation angle of the slit light with respect to the inner surface of the slit light irradiation and the imaging angle of the imaging optical axis, the imaging surface of the light receiving element is the imaging light. Tilted with respect to the axis ,
The imaging optical axis formed between the imaging prism and the slit light irradiation inner surface, and the optical axis formed between the slit light deflection means and the slit light irradiation inner surface are axes of the cylindrical inner surface. the inner surface measuring device that will be located on the same plane perpendicular to the direction. The cylindrical inner surface has a circumferential groove,
Irradiating the imaging prism to the maximum circle corresponding to the bottom surface of the circumferential groove and the minimum circle corresponding to the opening surface of the circumferential groove with respect to the irradiation direction of the slit light irradiated to the inner surface of the cylinder including the circumferential groove The inner surface measuring apparatus according to claim 1, wherein the inner surface measuring apparatus is disposed adjacent to the slit light deflecting unit so as to be inside the regular reflection optical axis of the slit light.

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