JP5089286B2 - Shape measuring device and shape measuring method - Google Patents

Description

  The present invention captures an image of a line light (image of a light cutting line) irradiated on the surface of a relatively moving object to be measured (such as the surface of a rotating tire), and uses a light cutting method based on the captured image. The present invention relates to a shape measuring apparatus and method for detecting the surface shape of an object to be measured by performing shape detection.

In production sites, it is often required to measure the surface shape (surface height distribution) of a product at high speed and without contact for the purpose of quality control of the product.
For example, a tire has a structure in which various materials such as rubber, chemical fiber, and steel cord are laminated, and if there is a non-uniform portion in the laminated structure, the tire is relatively pressure resistant when filled with air. In the weak part, a raised part (convex part) called a bulge and a hollow part (concave part) called a dent or a depression are generated. Tires with such shape defects as bulges and dents need to be inspected and excluded from shipment due to safety issues or poor appearance.
Conventionally, tire shape defects are inspected by detecting the surface height of multiple points with a contact or non-contact point measuring sensor while rotating the tire with a rotating machine, and determining the tire surface from the distribution of the surface height. It has been done by measuring the shape. However, in the inspection of shape defects based on tire shape measurement using point measurement type sensors, the shape of the entire surface to be detected for shape defects in tires is exhausted due to the restrictions on the number of sensors arranged and the inspection time. There was a problem that it was not possible to measure, and detection of shape defects was likely to occur.
On the other hand, in Patent Document 1, the surface of a rotating tire is irradiated with slit light (line light) to capture an image of the slit light, and the shape is detected by a light cutting method based on the captured image. A technique for measuring the surface shape of the film is shown. According to the technique disclosed in Patent Document 1, it is possible to comprehensively (continuously) measure the entire shape of a shape defect detection target surface (a tire sidewall surface or a tread surface) in a tire. Can be prevented from being missed.
As shown in Patent Document 1, in general, when shape detection is performed by a light cutting method, a single light cutting line (one line is irradiated with light) on a detection target surface (such as a sidewall surface of a tire). A single line light is irradiated from the detection height direction (the direction of the surface height to be detected) in the light cutting line so that the portion is formed with a camera arranged in a specific direction. An image of a linear line light (an image of a light cutting line) is captured.

In the production process of metal plates, thick plates and thin plates are produced through a rolling process in which metal materials such as steel, aluminum, and copper are rolled. In order to manage product quality, it is necessary to measure the surface shape of a strip-shaped metal material (hereinafter referred to as a rolled material) before and after passing through the rolling process at high speed and without contact while the rolled material is moving. It becomes important. Similarly, the surface shape of plate materials (thick plates and thin plates) that flow through hot rolling lines, cold rolling lines, wire rolling lines, etc., and slabs, blooms, billets, etc. before rolling are high-speed and non-contact. It is important for quality control to measure with.
Japanese Patent Laid-Open No. 11-138654

By the way, the tire surface (especially the sidewall surface) is black and has high glossiness, and the ratio of the scattered and reflected line light applied to the tire surface is relatively low. Further, the tire surface (particularly, the sidewall surface) is formed in a mountain shape as a whole, and it is necessary to reduce the aperture of the camera in order to obtain a necessary depth of field.
Therefore, in the tire surface shape measurement disclosed in Patent Document 1, in order to obtain a clear image of the line light irradiated on the tire surface, the intensity (light quantity) of the line light is increased or the image of the camera is captured. It is necessary to increase the exposure time by lowering the rate (slower shutter speed).
However, when the intensity of the line light is increased, there is a problem that the tire that is black and absorbs light may be thermally damaged. Furthermore, the use of a light source with high power (usually a laser light source) has a problem that a cooling device is required, which leads to an increase in size and cost of the device, and deteriorates maintainability.
In addition, if the image of the light section line is to be imaged with sufficient spatial resolution in the circumferential direction of the rotating tire within the limited time allowed for product inspection, the camera will be able to obtain a clear image of the line light. There has been a problem that the imaging rate (number of imaging per unit time) cannot be lowered.
For example, the inspection time allowed for a tire shape defect inspection is about 1 second. Further, in the measurement of the tire shape by the light cutting method, in order to distinguish the image of the light cutting line from the characters written on the tire surface, at least the line width (about 1 mm) of the characters in the circumferential direction of the rotating tire. It is necessary to perform imaging with a spatial resolution of. In order to satisfy the requirements of the inspection time and spatial resolution, it is necessary to capture 2000 frames per second for passenger car tires and 4000 frames per second for larger truck or bus tires. However, when imaging is performed at a high imaging rate of 4000 frames per second, a clear image of line light cannot be obtained by the technique disclosed in Patent Document 1.
In addition, even in the above-described metal product production process, if an image of the optical cutting line is to be imaged with sufficient spatial resolution on the surface of the material that moves within a limited time, it is necessary to image at a high imaging rate. There was a problem that a clear image of line light could not be obtained. Further, in order to complete the shape measurement within a limited time, there is a problem that the calculation load of image processing required for detecting the optical cutting line must be reduced so as to be able to cope with a high imaging rate.
Accordingly, the present invention has been made in view of the above circumstances, and the object of the present invention is to capture an image of line light (image of a light cutting line) irradiated on the surface of a relatively moving object to be measured. When measuring the surface shape of the object to be measured by detecting the shape based on the captured image based on the captured image, a sufficiently high imaging rate (for example, per second) without increasing the intensity of the line light. Even if the optical section line is imaged at 4000 frames or more), a clear image of the optical section line can be obtained, and further, calculation of image processing required for detecting the optical section line so as to be able to cope with such a high imaging rate. It is an object of the present invention to provide a shape measuring apparatus and a method for reducing the load.

In order to achieve the above object, a shape measuring apparatus according to the present invention captures an image of line light (image of a light section line) irradiated on the surface of a relatively moving object to be measured, and based on the captured image. This is a shape measuring device that measures the surface shape of the object to be measured by detecting the shape by the light cutting method, and includes the following components (1-1) to (1-4). .
(1-1) The direction of movement of the surface of the object to be measured is applied to the surface of the object by irradiating a plurality of line lights from a direction different from the detected height direction of the surface of the object to be measured. Line light irradiation that forms a plurality of separated light cutting lines that extend in a second direction orthogonal to the first direction and whose ranges occupied in the second direction are shifted from each other (that is, the center positions in the second direction are different) means.
(1-2) A direction in which principal rays of each of the plurality of line lights are specularly reflected with respect to the surface of the object to be measured, with respect to the images of the plurality of separated light cutting lines formed on the surface of the object to be measured. Imaging means for imaging in.
(1-3) For each of the plurality of captured images obtained by the imaging unit in response to the movement of a certain unit, in advance corresponding to each of the plurality of separated light cutting lines in the coordinate system of the captured image of the imaging unit. Light cutting line coordinate detection means for individually detecting light cutting line coordinates, which are the coordinates of the image of the light cutting line, from each of a plurality of set images of independent image processing target areas.
(1-4) Surface shape calculating means for calculating a surface height distribution in the first direction of the object to be measured based on the plurality of light cutting line coordinates detected by the light cutting line coordinate detecting means.
Note that “the surface of the object to be measured that moves relatively” means that the surface of the object to be measured itself is moved by linear movement or rotation of the object to be measured, and that the object to be measured is fixed. Thus, it means that the optical system for irradiating the line light and capturing the image thereof in the shape measuring apparatus moves along the surface of the object to be measured.

For example, when line light is irradiated onto the surface of a glossy object to be measured such as a tire or metal, the amount of specularly reflected light is larger than that of scattered reflected light directed in a specific direction (imaging range of the camera). Also, when the surface of the object to be measured is curved, an image of one line light having a long line length (image of a light cutting line) is regularly reflected from the principal ray of the line light (light along the center line). Even if the imaging means performs imaging in the direction, the specularly reflected light of the line light that is away from both sides from the principal ray does not reach the imaging means, and is away from the center of the entire image of the light section line. As for the portion, the amount of reflected light reaching the image pickup means is insufficient and a clear image cannot be obtained.
On the other hand, in the shape measuring apparatus according to the present invention, the imaging means captures an image of the light section line (line light image) in the regular reflection direction of the line light irradiated on the surface of the object to be measured. Even if imaging is performed at a sufficiently high imaging rate (for example, 4000 frames or more per second) without increasing the intensity of the line light, a clear image of the light section line can be obtained. In addition, the line light irradiating means irradiates the surface of the object to be measured with a plurality of line lights having a short line length occupying the longitudinal direction (the second direction) in a state shifted from each other. The imaging means is located in the regular reflection direction of the principal ray of each light. Therefore, according to the present invention, a clear image can be obtained with respect to the entire image of the plurality of light cutting lines over a relatively wide range in the second direction.

In the present invention, since a plurality of light cutting lines are separately formed on the surface of the object to be measured, a plurality of light beams whose intervals between the light cutting lines change according to the surface shape of the object to be measured. If a sufficient interval is set for the position variation width of the cutting line, a plurality of independent image processing target areas corresponding to a plurality of light cutting lines can be set in advance in the coordinate system of the captured image. it can. The “image processing target area corresponding to each of the plurality of optical cutting lines” shown here includes only an image of the optical cutting line corresponding to the area in the image processing target area. , Other than that, it means a region where no image of the light section line exists.
The plurality of independent image processing target regions corresponding to the plurality of separated light cutting lines are measured by, for example, measuring a measurement object for calibration whose shape is known in advance by the shape measuring device (the imaging unit). Imaging), and can be calculated from the positions (coordinates) of the images of the plurality of light cutting lines in the obtained captured image.
By the way, when irradiating a plurality of line lights on the surface of the object to be measured, it is conceivable to irradiate a plurality of line lights in a row so that one light cutting line is formed on the surface of the object to be measured. . Then, the surface shape of the object to be measured can be measured only by performing image processing based on the light cutting method that is generally performed on the image of the single light cutting line.
However, it is necessary to align the optical system of each of the plurality of line lights with high accuracy so that one light cutting line is formed on the surface of the object to be measured. Invite the deterioration.

FIG. 10 schematically shows a state in which positional deviation occurs in the images v1 to v3 of the light cutting lines when a plurality of light cutting lines are formed on the surface of the object to be measured to form one light cutting line. FIG. FIG. 10 shows an example in which there are three light cutting lines (three line lights to irradiate), but cases where the number of light cutting lines is two or four or more are also conceivable.
As shown in FIG. 10, when a positional shift (a portion surrounded by a wavy line in the figure) occurs in the images v1 to v3 of the plurality of light cutting lines, a direction (in FIG. 10) orthogonal to the longitudinal direction of the light cutting lines. In a simple process (normally performed process) in which the position of the pixel with the highest luminance is detected for each line in the X-axis direction), the position (coordinates) of the image of the light section line cannot be detected correctly.
In addition, it is possible to allow a slight misalignment between the positions v1 to v3 of the plurality of light cutting lines on the surface of the object to be measured, and the coordinate detection processing (image processing) of the light cutting lines in consideration of the position shifts. If this is done, the computational load increases, and depending on practical (relatively cheap) circuits and processors, high-speed image processing corresponding to a high imaging rate (for example, 4000 frames or more per second) becomes difficult. .
On the other hand, in the present invention, the light cutting line coordinate detecting means detects the coordinates of the plurality of separated light cutting line images from the images of the plurality of independent image processing target areas. The coordinates of the image of the light section line can be detected by a simple process (high-speed process) in which the position of the pixel with the highest luminance is detected for each line. In other words, even if an image of the light section line is taken at a high imaging rate, a clear image of the line light irradiated on the surface of the object to be measured can be obtained, and further, such a high imaging rate can be handled. It is possible to reduce the computational load of image processing required for detecting the light section line.

Further, in the present invention, for each position (coordinate) in the second direction, according to the movement in a certain unit (for example, in the case where the object to be measured is a rotating tire, a constant angular cycle of the rotation). If the surface height of the object to be measured calculated from a plurality of the detected light cutting line coordinates is arranged, it represents the surface height distribution in the first direction. Therefore, at least the surface height distribution in the first direction can be calculated by the surface shape calculation means.
In the inspection of the surface of the object to be measured, if it is sufficient to obtain a one-dimensional profile of the first direction (the moving direction of the surface of the object to be measured) at each position in the second direction, the surface shape calculation The calculation result of the means can be used.

Further, the shape measuring apparatus according to the present invention includes a plurality of sets of the first line light irradiating means for irradiating the line light and capturing an image of the line light in parallel on each of a plurality of surfaces of the object to be measured; It is conceivable to have a set of imaging means.
Thereby, the shape measurement of a plurality of surfaces (for example, the sidewall surface and tread surface of the tire) of the object to be measured can be performed simultaneously, and the time required for the shape measurement of the entire detection target surface of the object to be measured can be shortened.
In this case, it is preferable that the plurality of line light irradiation units corresponding to the plurality of surfaces of the object to be measured output the line light having different wavelengths.
For example, it is conceivable to extract an image of a corresponding wavelength (color) as a line light image by a predetermined image processing unit for each captured image of the plurality of imaging units. Alternatively, it is conceivable that the shape measuring apparatus includes an optical filter that selectively transmits light of a corresponding wavelength in the optical path of incident light to each of the plurality of imaging units.
Thereby, it can prevent that the line light used by the other surface in the shape measurement of a certain surface turns into noise light about the several surface of a to-be-measured object.

In addition, it is more preferable that the shape measuring apparatus according to the present invention further includes a component shown in either of the following (1-5) or (1-6).
(1-5) Collimating means for collimating each of a plurality of line lights irradiated on the surface of the measurement object by the line light irradiation means in the line length direction.
(1-6) A condensing unit that condenses each of the plurality of line lights irradiated on the surface of the measurement object by the line light irradiation unit in the line length direction.
As a result, even if the length of each of the plurality of line lights irradiated on the surface of the curved object to be measured is slightly increased, the specular reflection direction of the light rays away from both sides from the principal ray is set to the direction of the imaging means. Can be approached. As a result, the number of line lights can be reduced and the apparatus can be simplified.
Moreover, in the shape measuring apparatus according to the present invention, the line light irradiating means has an end in the second direction (longitudinal direction of the optical cutting line) between the adjacent objects in the second direction on the surface of the object to be measured. It is conceivable to form the plurality of separated light cutting lines where the positions of the portions overlap.
Thereby, measurement data of the shape (height distribution) of the surface of the object to be measured can be obtained without loss (continuously) in the second direction.
Further, in the shape measuring apparatus according to the present invention, the light cutting line coordinate detecting means calculates the coordinates of the highest luminance pixel for each line in the first direction for each of the images of the plurality of independent image processing target areas. It is conceivable to detect the light cutting line coordinates by detection.
Thereby, the coordinates of the light cutting line can be detected by a simple process with a low calculation load.

If the variation (individual difference) in the surface shape (surface height) of the object to be measured is small with respect to the interval between the plurality of light cutting lines, the image processing target areas corresponding to the plurality of light cutting lines, respectively. Even if the coordinates of are fixed, there is no particular problem. However, when the variation in the surface shape is large, if the coordinates of the plurality of image processing target areas are fixed, the position of the light cutting line deviates from the corresponding image processing target area (hereinafter referred to as the out-of-area state). There is a risk that the optical cutting line cannot be detected normally. However, for objects to be measured whose surface shape changes slowly, such as tires, even if the surface shape varies greatly, the multiple optical cutting lines are within a small variation range with respect to each other. Thus, the overall position (especially the position in the first direction) greatly fluctuates.
Therefore, it is more preferable that the shape measuring apparatus according to the present invention further includes the constituent elements shown in the following (1-7).
(1-7) detecting a position of a pixel having a luminance of a predetermined level or more in one or a plurality of predetermined trial areas in a captured image obtained by imaging the object to be measured by the imaging unit; By shifting the coordinates of a plurality of predetermined independent reference areas in the captured image obtained by imaging the object to be calibrated by the above according to the detection position of the pixel having the luminance of the predetermined level or more, the plurality Image processing target area automatic setting means for automatically setting the coordinates of the independent image processing target areas.
As described above, the coordinates of the plurality of independent reference regions corresponding to the case where the surface height of the object to be measured is a predetermined reference height are set in advance, and the surface shape of the object to be measured greatly varies. However, with respect to an image of an area (the predetermined area) where only one specific light cutting line can be expected to pass through the area, the position of a pixel having a luminance of a predetermined level or higher (that is, the specific one A position of a part of the light section line) is detected, and based on the detected position, a shift from the coordinates of the reference area (particularly the coordinates corresponding to the first direction) to the coordinates of the image processing target area is performed. For example, it is possible to avoid the out-of-region state.

In the present invention, since a plurality of light cutting lines are separately formed on the surface of the object to be measured, the shape of the surface of the object to be calculated calculated from each of the plurality of light cutting lines in one captured image (described above) The height distribution in the second direction (one-dimensional profile) is a mixture of different positions in the first direction (positions shifted in the first direction by a predetermined amount of movement). Therefore, in the inspection of the surface of the object to be measured, when a two-dimensional profile (the first direction and the second direction) of the surface of the object to be measured is required, the shape measuring apparatus according to the present invention can perform the following (1 What is necessary is just to provide the structure shown to -8).
(1-8) The surface shape calculation unit is configured to detect a positional deviation amount in the first direction between the plurality of light cutting line coordinates detected by the light cutting line coordinate detection unit and the plurality of separated light cutting lines. The surface height distribution in the first direction and the second direction of the object to be measured is calculated on the basis of the set shift information set in advance for the shift amount of the movement corresponding to.
Note that the shift amount of the movement is, for example, an image processing based on a captured image obtained by measuring a measurement object for calibration whose shape is known in advance (imaging by the imaging unit) with the shape measuring device. Can be calculated.

In addition, when the object to be measured is a tire, in the measurement of the shape of the sidewall surface of the tire where characters are written on the surface, as described above, in order to distinguish between the characters and the image of the line light, high imaging is required. It is necessary to ensure high spatial resolution by performing imaging at a rate. The present invention is suitable for application to such a detection target.
Therefore, when the object to be measured is a tire, it is preferable that the shape measuring apparatus according to the present invention has the following configuration.
That is, the line light irradiation means includes a first line light irradiation means for forming the plurality of separated light cutting lines extending in the second direction substantially parallel to a radial direction of the tire on a sidewall surface of the tire. Prepare. Furthermore, the imaging means includes first imaging means for capturing images of the plurality of separated light cutting lines formed on the sidewall surface of the tire by the first line light irradiation means.
Thereby, the shape of the sidewall surface of the tire can be detected at high speed and with high spatial resolution.
In addition, when the object to be measured is a tire, the shape measuring apparatus according to the present invention may further include the following configuration.
That is, the line light irradiating means forms the plurality of separated light cutting lines extending in the second direction substantially parallel to a direction orthogonal to the tire circumferential direction on the tire tread surface. Irradiation means is provided. Furthermore, the image pickup means includes second image pickup means for picking up images of the plurality of separated light cutting lines formed on the tread surface of the tire by the second line light irradiation means.

Further, the present invention captures an image of line light irradiated on the surface of a relatively moving object to be measured using the shape measuring apparatus described above, and detects the shape by a light cutting method based on the captured image. It can also be grasped as a shape measuring method for detecting the surface shape of the object to be measured.
That is, the shape measuring method according to the present invention is a measuring method for executing the following steps (2-1) to (2-4).
(2-1) The direction of movement of the surface of the object to be measured is applied to the surface of the object by irradiating a plurality of line lights from a direction different from the detected height direction of the surface of the object to be measured. Line light irradiation means for forming a plurality of separated light cutting lines extending in a second direction orthogonal to the first direction and occupying ranges in the second direction are formed on the surface of the object to be measured. In addition, the image pickup means for picking up the images of the plurality of separated light cutting lines, the field of view of the image pickup means in a direction in which light along the principal ray of each of the plurality of line lights is regularly reflected on the surface of the object to be measured. With the line light irradiating means irradiating the surface of the object to be measured with the plurality of line lights, the plurality of separated light cutting line images are moved in a certain unit. According to the imaging hand Line light irradiation, an imaging step of imaging the.
(2-2) With respect to each of the plurality of captured images obtained by the line light irradiation / imaging process by a predetermined calculation unit, each of the plurality of separated light cutting lines in the coordinate system of the captured image of the imaging unit. A light cutting line coordinate detection step of individually detecting light cutting line coordinates, which are coordinates of the image of the light cutting line, from each of the plurality of independent image processing target areas set in advance.
(2-3) A surface shape calculation step of calculating a surface height distribution of the object to be measured based on the plurality of light cutting line coordinates detected by the light cutting line coordinate detection step by a predetermined calculation means.
Thereby, the shape measuring method according to the present invention has the same effects as the shape measuring apparatus according to the present invention.

According to the present invention, an object to be measured is obtained by capturing an image of line light irradiated on the surface of a glossy object to be measured such as a tire or a metal member, and performing shape detection by a light cutting method based on the captured image. When detecting the surface shape of the object, even if the line light image is captured at a sufficiently high imaging rate (for example, 4000 frames or more per second) without increasing the line light intensity, A clear image of line light irradiated on the surface can be obtained. As a result, the surface shape can be detected at high speed and with high spatial resolution without causing thermal damage to the object to be measured.
Furthermore, according to the present invention, since the coordinates of the plurality of separated light cutting line images are detected from the images of the plurality of independent image processing target areas, for example, the pixel having the highest luminance for each line. The coordinates of the image of the light section line can be detected by a simple process (high-speed process) of detecting the position of. As a result, it is possible to reduce the computational load of image processing required for detecting the optical cutting line so as to be compatible with a high imaging rate.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a diagram showing a schematic configuration of a shape measuring apparatus W according to an embodiment of the present invention, and FIG. 2 is a diagram schematically showing a three-dimensional arrangement of light sources and cameras in a sensor unit provided in the shape measuring apparatus W. FIG. 3 is a diagram schematically showing the arrangement of the line light source and the camera in the sensor unit when viewed from a specific direction (Y-axis direction), and FIG. 4 shows the tire surface at the position where the main ray of the line light reaches. FIG. 5 schematically shows the arrangement of the line light source and the camera in the sensor unit when viewed from the vertical direction, FIG. 5 schematically shows how the line light is collimated in the sensor unit, and FIG. 6 shows the sensor. FIG. 7 schematically shows an example of a tire image captured by a camera in the shape measuring device W, and FIG. 8 shows a shape measuring device. FIG. 9 is a diagram schematically illustrating the distribution of measurement data obtained by W and the state of data shift. FIG. 9 is a diagram schematically illustrating an example of a captured image of an object to be calibrated by a camera in the shape measuring apparatus W. FIG. 10 is a diagram schematically showing a state in which a position shift occurs in a light cutting line when a plurality of light cutting lines are formed on the surface of the object to be measured to form one light cutting line.

First, the overall configuration of the shape measuring apparatus W according to the embodiment of the present invention will be described with reference to FIG.
The shape measuring apparatus W according to the embodiment of the present invention takes images v1 to v3 (images of light cutting lines) of line light irradiated on the surface of a rotating tire 1 (an example of an object to be measured) with a camera, It is an apparatus that detects the surface shape of the tire 1 by performing shape detection by a light cutting method based on a captured image. As the tire 1 rotates around its rotation axis 1g, the surface of the tire 1 moves relative to the line light and the camera.
As shown in FIG. 1, the shape measuring device W includes a tire rotating machine 2, a sensor unit 3, a unit driving device 4, an encoder 5, an image processing device 6, and the like.
The tire rotating machine 2 is a rotating device such as a motor that rotates the tire 1 that is the object of shape measurement about the rotation shaft 1g. For example, the tire rotating machine 2 rotates the tire 1 at a rotation speed of 60 rpm. As a result, the shape measuring device W detects the surface shape of the entire circumference range of the tread surface and the sidewall surface of the tire 1 by the sensor unit 3 to be described later during one second in which the tire 1 is rotated once.
The sensor unit 3 is a unit in which a light source that irradiates line light onto the surface of the rotating tire 1 and a camera that captures an image of a light cutting line (line light image) on the surface of the tire 1 are incorporated. In the present embodiment, two sensor units 3a and 3c used for measuring the shape of each of the two sidewall surfaces of the tire 1 and one sensor unit 3b used for measuring the shape of the tread surface of the tire 1 are combined. Two sensor units 3 are provided. Details of these sensor units 3 will be described later.

The unit driving device 4 is a device for supporting each sensor unit 3 movably by using a driving device such as a servo motor as a driving source, and positioning the position of each sensor unit 3 with respect to the tire 1. The unit driving device 4 moves each sensor unit 3 before the tire 1 is attached to or detached from the tire rotating machine 2 according to an operation on a predetermined operation unit or a control command from an external device. After a new tire 1 is mounted on the tire rotating machine 2, the sensor unit 3 is positioned at a predetermined inspection position close to the tire 1.
The encoder 5 is a sensor for detecting the rotation angle of the rotating shaft of the tire rotating machine 2, that is, the rotation angle of the tire 1, and the detection signal is used for controlling the imaging timing of the camera provided in the sensor unit 3. It is done.
The image processing device 6 performs shutter control (control of imaging timing) of the camera provided in the sensor unit 3 based on the detection signal of the encoder 5. For example, the image processing device 6 releases the shutter of the camera every time the encoder 5 detects that the tire 1 rotating at a speed of 60 rpm has rotated by 0.09 ° (= 360 ° / 4000). Control as follows. Thereby, imaging is performed at an imaging rate of 4000 frames per second.
Furthermore, the image processing device 6 inputs data of an image captured by a camera provided in the sensor unit 3, that is, an image of a line light (image of a light cutting line) irradiated on the surface of the tire 1. Based on the captured image, shape detection processing by a light cutting method is executed, and shape data (data representing the height distribution on the surface of the tire 1) as a result of detection is output to a host computer (not shown). At that time, the image processing device 6 performs predetermined image processing on the sidewall surface of the tire 1 to remove the character image written therein and extract only the line light image. Then, based on the extracted line light image, the shape detection process by the light cutting method is executed. The image processing apparatus 6 is realized by, for example, an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).
Then, the host computer determines whether or not the surface shape detected for each surface of the tire 1 satisfies an allowable condition set in advance for each surface of the tire 1, and the determination result is displayed in a predetermined manner. Displayed on the unit or output as a predetermined control signal.
In addition, since the shape detection process by a light cutting method is known, description is abbreviate | omitted here.

Next, the sensor unit 3 will be described with reference to FIGS.
As shown in FIG. 2, the sensor unit 3 includes a light projecting device 10 that outputs a plurality of line lights, and a camera 20.
In FIG. 2, the X axis is the direction in contact with the circumference of the tire rotation at the shape measurement position of the tire 1, the Z axis is the detected height direction (the direction of the surface height to be detected) at the shape measurement position of the tire 1, and the Y axis is A direction perpendicular to the X axis and the Z axis is represented.
That is, in the sensor units 3a and 3c used for measuring the shape of the sidewall surface of the tire 1, the Z axis is the direction of the rotating shaft 1g of the tire 1, and the Y axis is the radial direction of the tire 1 (the rotation of the tire 1). The direction of the normal to the axis 1g).
In the sensor unit 3 b used for measuring the shape of the tread surface of the tire 1, the Z axis is the radial direction of the tire 1, and the Y axis is the direction of the rotation axis 1 g of the tire 1.

The light projecting device 10 includes a plurality of (three in FIG. 2) line light sources 11 to 13, and the plurality of line light sources 11 to 13 divide the same number (plurality) of light cutting lines Ls 1 on the surface of the tire 1. It is an apparatus that irradiates from a direction different from the detection height direction (Z-axis direction) in the light cutting lines Ls1 to Ls3 so that .about.Ls3 is formed.
FIG. 7 is a diagram schematically illustrating an example of a captured image of the tire 1 by the camera 20. As shown in FIG.
As shown in FIG. 7, the light projecting device 10 is provided on the surface of the tire 1 in the Y-axis direction (corresponding to the first direction) perpendicular to the X-axis direction (corresponding to the first direction) that is the movement direction of the surface of the tire 1 due to the rotation. A plurality of separated light cutting lines Ls1 to Ls3 (which correspond to the second direction) and their ranges in the Y-axis direction are shifted from each other (that is, the center positions in the Y-axis direction are different from each other) ( An example of the line light irradiation means). The coordinates in the X-axis direction of each of the light cutting lines Ls <b> 1 to Ls <b> 3 vary according to the surface height of the tire 1.
Further, as shown in FIG. 7, the light projecting device 10 is configured so that the adjacent ones on the surface of the tire 1 in the Y-axis direction are located at the ends in the Y-axis direction (longitudinal direction of the light cutting lines Ls <b> 1 to Ls <b> 3). A plurality of separated light cutting lines Ls1 to Ls3 are formed. Thereby, the measurement data of the shape (height distribution) of the tire surface can be obtained without missing (continuously) on the Y axis.
In the example shown in FIG. 7, the coordinates in the X-axis direction of some of the light cutting lines Ls1 and Ls3 are substantially the same, but the coordinates in the X-axis direction of all the light cutting lines Ls1 to Ls3 may be different. Conceivable.

The camera 20 includes a camera lens 22 and an image sensor 21 (light receiving unit), and a plurality of line light images v <b> 1 to v <b> 3 (light cutting line images) irradiated on the surface of the tire 1. Imaging is performed in the direction in which the principal rays Li1 to Li3 of the line lights are regularly reflected with respect to the surface of the tire 1 (an example of the imaging unit).
Therefore, in the sensor units 3a and 3c for the sidewall surface, the light projecting device 10 includes a plurality of light cutting lines Ls1 to Ls3 in the Y-axis direction parallel to the radial direction of the tire 1 on the sidewall surface of the tire 1. Are formed from a direction different from the detection height direction (Z-axis direction) by the light cutting lines Ls1 to Ls3 (an example of the first line light irradiation means).
On the other hand, in the sensor unit 3b for the tread surface, the light projecting device 10 includes a plurality of lights in the Y-axis direction, which is a direction orthogonal to the tire circumferential direction (the tire surface moving direction) on the tread surface of the tire 1. A plurality of line lights are irradiated from a direction different from the detection height direction (Z-axis direction) by the light cutting lines Ls1 to Ls3 so that the cutting lines Ls1 to Ls3 are formed (the second line light irradiation means). Example).
In the present embodiment, the irradiation of three line lights is illustrated for each surface of the tire 1 (for each sensor unit 3). However, by increasing or decreasing the number of the line light sources 11 to 13, It is also conceivable to irradiate two line lights or four or more line lights on each surface of one.

Further, the light projecting device 10 and the camera 20 are configured so that the principal rays (lights along the center line) of the plurality of line lights output from the line light sources 11 to 13 are applied to the surface of the tire 1 by a holding mechanism (not shown). Thus, the field of view of the camera 20 is held in the direction of regular reflection. Thereby, the camera 20 captures the images v1 to v3 of the plurality of light cutting lines in the direction in which the principal rays of the plurality of line lights are regularly reflected with respect to the surface of the tire 1 (an example of the imaging unit). For example, the positional relationship between the light projecting device 10 and the camera 20 is set such that the position and orientation of the camera 20 is set in a direction different from the detection height direction of the light section line, and then the regular reflection of the principal ray of each line light is performed. It can be considered that the design is performed by a process of setting the positions and orientations of the line light sources 11 to 13 in the light projecting device 10 so that the light is directed to the imaging range of the camera 20. Of course, the positional relationship between the light projecting device 10 and the camera 20 may be determined by the reverse procedure.
That is, the camera 20 in the sensor unit 3a, 3c for the side wall surface has a plurality of line light images v1 to v3 (images of light cutting lines Ls1 to Ls3) irradiated to the side wall surface of the tire 1 by the line light source 10. ) In the direction in which the principal ray of each of the plurality of line lights is regularly reflected with respect to the sidewall surface (an example of the first imaging means).
Further, the camera 20 in the sensor unit 3b for the tread surface uses a plurality of line light images v1 to v3 irradiated to the sidewall surface of the tire 1 by the line light source 10, and the principal ray of each of the plurality of line lights. Imaging is performed in the direction of regular reflection with respect to the sidewall surface (an example of the first imaging unit).

3 and 4 are diagrams schematically showing the arrangement of the line light source 10 and the camera 20 in the sensor unit 3. FIG. 3 shows the principal rays of the line light when viewed from the Y-axis direction. This represents a state when the arriving positions P1, P2 and P3 (hereinafter referred to as principal ray arrival positions) are viewed from a direction perpendicular to the tire surface. 3 (a), 4 (a) and 4 (c) are diagrams of the sensor units 3a and 3b for the sidewall surface, and FIGS. 3 (b) and 4 (b) are for the tread surface. It is a figure about the said sensor unit 3b.
As shown in FIGS. 3A and 3B, in the sensor unit 3 for both the sidewall surface and the tread surface, when viewed from the Y-axis direction, principal rays Li1, Li2, A line connecting the angle formed by Li3 with respect to the Z axis (or the angle formed with respect to the surface of the tire 1) and the corresponding principal ray arrival positions P1, P2, P3 and the center of the image sensor 21 of the camera 20 Each of the line light sources 11 to 13 and the camera are set so that the angle (or the angle formed with respect to the surface of the tire 1) formed by the imaging center lines Lo1, Lo2, and Lo3 (hereinafter referred to as imaging center lines Lo1, Lo2, and Lo3) is equal. 20 is held.
Further, as shown in FIGS. 4A to 4C, in the sensor unit 3 with respect to both the sidewall surface and the tread surface, the principal ray arrival positions P1, P2, and P3 from the direction perpendicular to the tire surface. When viewed, the line light sources 11 to 13 and the camera 20 are arranged such that the principal rays Li1, Li2, Li3 in each of the plurality of line lights and the corresponding imaging center lines Lo1, Lo2, Lo3 form one straight line. Is retained.
The positional relationship between the light projecting device 10 and the camera 20 described above is set with reference to the surface of the tire 1 (the surface of the principal ray arrival positions P1 to P3) to which the principal ray of the line light reaches. Shown as positional relationship. The positional relationship does not mean that the positions of the light projecting device 10 and the camera 20 are set for each tire 1 that is a subject, and the average surface shape of the tire 1 to be inspected is used as a reference. Means that it is set as For example, assuming a virtual reference surface representing an average surface shape of the tire 1 to be inspected, the light projecting device 10 and the camera 20 are connected to the main lines of the plurality of line lights irradiated on the surface of the tire 1. The light beam is held by a predetermined holding mechanism so that the imaging range of the camera 20 is positioned in a direction in which the light ray is regularly reflected with respect to the reference plane.

  On the other hand, the image processing device 6 is inspected every time the encoder 1 detects that the tire 1 has been rotated by a certain unit angle (for example, 0.09 °) while the tire 1 is rotated once (that is, constant). For each of a plurality of captured images (images for one rotation (360 degrees)) obtained by the camera 20 with a plurality of preset independent image processing targets in the coordinate system of the captured images of the camera 20 A light cutting line coordinate detection process for individually detecting coordinates (hereinafter referred to as light cutting line coordinates) of the images v1 to v3 of the light cutting lines Ls1 to Ls3 from the respective images of the areas A1 to A3 (see FIG. 7). (An example of the light cutting line coordinate detection means). Here, the plurality of independent image processing target areas A1 to A3 are areas whose coordinates are set in advance corresponding to the plurality of separated light cutting lines Ls1 to Ls3 formed on the surface of the tire 1, respectively.

As shown in FIG. 7, the shape measuring apparatus W forms a plurality of light cutting lines Ls <b> 1 to Ls <b> 3 separately on the surface of the tire 1. For this reason, if the space | interval between these light cutting lines Ls1-Ls3 is set to a sufficient space | interval with respect to the position fluctuation width of several light cutting lines Ls1-Ls3 which changes according to the surface shape of the tire 1, In the coordinate system of the captured image of the camera 20, a plurality of independent image processing target areas A1 to A3 corresponding to the plurality of light cutting lines Ls1 to Ls3 can be set in advance.
In the example shown in FIG. 7, an area A1 whose X coordinate is greater than or equal to x1 and whose Y coordinate is less than y1 is an area corresponding to the light cutting line Ls1. An area A2 having an X coordinate less than x1, a Y coordinate greater than or equal to y1, and less than y2 is an area corresponding to the light cutting line Ls2. Similarly, a region A3 having an X coordinate of x1 or more and a Y coordinate of y2 or more is a region corresponding to the light section line Ls3. In the image processing target areas A1 to A3, only the images v1 to v3 of the optical cutting lines Ls1 to Ls3 corresponding to the areas on a one-to-one basis exist in the images of the image processing target areas A1 to A3. This is a region where there is no image of a light cutting line other than.
The plurality of independent image processing target areas A1 to A3 are obtained by, for example, performing measurement (imaging by the camera 20) of a calibration object to be measured whose shape is known in advance by the shape measuring device W. Is calculated based on the positions (coordinates) of the images v1 to v3 of the plurality of light cutting lines Ls1 to Ls3 and the estimated width of the variation range of the surface shape of the tire 1, and is stored in the memory of the image processing device 6.

Further, the image processing device 6 has the highest luminance pixel for each line in the X-axis direction (the movement direction of the tire surface, corresponding to the first direction) for each of the plurality of independent image processing target areas A1 to A3. The light cutting line coordinates are detected by detecting the coordinates. As described above, the image processing apparatus 6 detects the coordinates of the images v1 to v3 of the plurality of separated light cutting lines Ls1 to Ls3 from the images of the plurality of independent image processing target areas A1 to A3. The coordinates of the images v1 to v3 of the light cutting lines Ls1 to Ls3 can be detected by a simple process (high speed process) of detecting the position of the pixel with the highest luminance for each line. As a result, even if the images of the light cutting lines Ls1 to Ls3 are captured at a high imaging rate (for example, 4000 frames per second), the image processing required for the detection of the light cutting line so as to cope with such a high imaging rate. Calculation load can be reduced.
The Y coordinates of the light cutting lines Ls1 to Ls3 obtained as described above are the longitudinal positions of the light cutting lines Ls1 to Ls3, that is, the radial position of the tire 1 on the sidewall surface of the tire 1, On the tread surface of the tire 1, the position of the tire 1 in the rotation axis direction is shown. Further, the X coordinate of each of the light cutting lines Ls <b> 1 to Ls <b> 3 represents the surface height of the tire 1.

Then, the image processing device 6 calculates the X coordinate for the coordinates of the light cutting lines Ls1 to Ls3 detected from the captured image (a plurality of light cutting line coordinates detected in accordance with the rotation angle) by using a preset conversion coefficient. Converted into the height of the surface, the shape information of the tire surface after conversion, that is, the information on the rotation angle of the tire 1 (for example, the count number of the encoder 5), the Y coordinate of the light cutting lines Ls1 to Ls3, and the tire surface height Is output to the host computer.
Here, for each position (coordinate) in the Y-axis direction (corresponding to the second direction), calculation is performed from a plurality of the light cutting line coordinates detected according to the rotation angle of the tire 1 (with a constant angular period). If the surface height of the tire 1 is arranged, it represents a one-dimensional surface height distribution in the moving direction of the tire surface. Accordingly, the information on the rotation angle of the tire 1, the Y coordinate of the light cutting lines Ls1 to Ls3, and the tire surface height are related to the surface height distribution in the moving direction of the surface of the tire 1 (corresponding to the first direction). It is information to represent. The image processing device 6 that executes processing for converting the X coordinate into the surface height of the tire 1 is an example of the first surface shape calculating means.

When setting the conversion coefficient for converting the X coordinate of the optical cutting lines Ls1 to Ls3 into the surface height of the tire 1, for example, the shape measuring device W measures the measurement object for calibration whose shape is previously known (camera 20). The conversion coefficient is calculated from the correspondence between the positions (coordinates) of the images of the plurality of light cutting lines Ls1 to Ls3 in the obtained captured image and the surface height of the calibration object, The calculation result is stored in the memory of the image processing device 6.
Alternatively, a conversion coefficient for converting the surface height of the tire 1 into the X coordinate of the light cutting lines Ls1 to Ls3 by measuring the calibration object is calculated in advance and stored in the memory of the host computer. In a computer, it is also conceivable to evaluate the surface shape of the tire by the magnitude of the X coordinate.

By the way, in the inspection of the tire surface, if it is sufficient to obtain a one-dimensional profile in the X-axis direction (the movement direction of the tire surface) at each position in the Y-axis direction, It is sufficient to perform conversion.
On the other hand, in the inspection of the tire surface, when a two-dimensional (X-axis direction and Y-axis direction) profile of the tire surface is required, it is not sufficient to convert only the X coordinate to the surface height.
FIG. 8 is a diagram schematically showing the distribution of measurement data obtained by the shape measuring apparatus W and the state of data shift.
FIG. 8A shows the tire surface height information for each of the image processing target areas A1 to A3, the information on the rotation angle of the tire 1 at the time of data measurement (the rotation angle or the count number of output pulses of the encoder 5). Is a diagram schematically showing a state in which the horizontal axis of the graph is arranged and the Y coordinate (longitudinal direction of the optical cutting line) of the light cutting lines Ls1 to Ls3 is arranged as the vertical axis of the graph.

In the shape measuring apparatus W, as shown in FIG. 7, since the light cutting lines Ls1 to Ls3 corresponding to the image processing target areas A1 to A3 are separately formed, a plurality of light cuttings in one captured image are performed. The tire surface shape (height distribution in the longitudinal direction of the light cutting line) calculated from each of the lines Ls1 to Ls3 includes a mixture of different positions in the tire surface movement direction (X-axis direction). In FIG. 8, a part of the measurement data d11, d31 for each of the areas A1 and A3 and a part of the measurement data d21 for the area A2 are data in which the positions in the movement direction of the tire surface coincide with each other. Represent. Similarly, a part of the measurement data d12, d32 for each of the areas A1 and A3 and a part of the measurement data d22 for the area A2 indicate that the positions in the moving direction of the tire surface coincide with each other. The example shown in FIG. 8 is an example in the case where there is no positional deviation in the X-axis direction of the measurement data corresponding to the image processing target areas A1 and A3.
As shown in FIG. 8A, when the amount of displacement of the position in the tire surface movement direction (X-axis direction) converted into the rotation angle is the shift amount θs of the tire rotation angle, as shown in FIG. In order to match the positions in the X-axis direction (tire surface movement direction) on the tire surface between the measurement data corresponding to A2 and A2, the rotation angle at the time of measurement must be shifted by θs.
FIG. 8B shows the tire surface corresponding to each of the image processing target areas A1 to A3 after the rotation angle at the time of measurement is shifted by θs for the measurement data corresponding to the image processing target areas A1 and A2. Schematic representation of height information arranged with the position information in the moving direction on the tire surface as the horizontal axis of the graph and the Y coordinate of the optical cutting lines Ls1 to Ls3 (longitudinal direction of the optical cutting line) as the vertical axis of the graph FIG.

Therefore, in the shape measuring device W, the image processing device 6 or the host computer detects a plurality of the light cutting line coordinates detected by the image processing device 6 according to the rotation angle of the tire 1 and a plurality of separated light cutting lines. Based on the setting information (hereinafter referred to as angle shift information) relating to the shift amount θs of the tire rotation angle corresponding to the positional deviation amount in the X-axis direction (corresponding to the first direction) between Ls1 to Ls3, the X of the tire 1 It is also conceivable to calculate the surface height distribution in the axial direction (the first direction) and the Y-axis direction (the second direction) (an example of the second surface shape calculating means). Here, the angle shift information is the shift amount θs of the tire rotation angle or information corresponding thereto, and is preset information (information stored in advance in the image processing device 6 or the memory of the host computer). Note that the angle shift information includes a rotational shift amount (here, a rotational angle shift) corresponding to a positional shift amount in the X-axis direction (corresponding to the first direction) between the plurality of separated light cutting lines Ls1 to Ls3. Amount), which is information set in advance, and is an example of the setting shift information.
More specifically, the image processing apparatus 6 or the host computer, as described above, the image processing apparatus 6 uses a conversion factor set in advance for a plurality of light cutting line coordinates detected according to the rotation angle. In accordance with the process of converting the X coordinate into the height of the tire surface and the angle shift information set in advance, a plurality of light cutting line coordinates detected for each of the image processing target areas A1 to A3 are used as the tire rotation angle shift amount θs. By performing a process of shifting each other by a corresponding amount, the surface height distribution in the moving direction (the first direction) of the surface of the tire 1 and the direction orthogonal to the moving direction (the second direction) is calculated.

Further, the shift amount θs of the tire rotation angle is measured by measuring the object to be calibrated whose shape is known in advance (imaging by the camera 20) by the shape measuring device W, and performing image processing based on the obtained captured image. It is the information calculated by.
FIG. 9 is a diagram schematically illustrating an example of a captured image obtained by capturing an object to be measured whose calibration is known with the camera of the shape measuring apparatus W.
The measurement object for calibration corresponding to the captured image shown in FIG. 9 has a flat measurement surface, and a scale mk representing the rotation angle of the tire is written on the measurement surface.
The shape measuring device W previously measures the object to be calibrated (imaged by the camera 20) in advance, and the obtained imaged image has a misalignment width in the X-axis direction between the optical cutting lines Ls1 to Ls3. Is read by the memory mk, the read angle becomes the shift amount θs of the tire rotation angle.

In the measurement using the shape measuring device W, if the variation (individual difference) in the tire surface shape (the height of the tire surface) is small with respect to the distance between the plurality of light cutting lines Ls1 to Ls3, the plurality of light cutting lines. Even if the coordinates of the image processing target areas A1 to A3 corresponding to Ls1 to Ls3 are fixed, no particular problem occurs.
However, when the variation in the tire surface shape is large, if the coordinates of the plurality of image processing target areas A1 to A3 are fixed, the positions of the light cutting lines Ls1 to Ls3 correspond to the corresponding image processing target areas A1 to A3. Therefore, the coordinates of the light cutting lines Ls1 to Ls3 may not be normally detected.
However, due to the characteristic that the surface shape of the tire 1 changes slowly, when the variation in the tire surface shape is large, the plurality of light cutting lines Ls1 to Ls3 are kept within a small variation range with respect to each other. As a result, the overall position (particularly, the position in the X-axis direction) varies greatly.

Therefore, in the shape measuring apparatus W, it is conceivable that the image processing apparatus 6 executes a process of automatically setting the coordinates of the image processing target areas A1 to A3 in advance (before the main measurement) (the image processing target area). An example of automatic setting means).
More specifically, the image processing device 6 detects the position of a pixel having a luminance equal to or higher than a predetermined setting level in one or a plurality of predetermined areas A0 (hereinafter referred to as trial areas) in the captured image of the camera 20. The coordinates of a plurality of independent reference areas set in advance (reference areas corresponding to the respective image processing target areas A1 to A3) are set in accordance with the detection positions of pixels having a luminance level equal to or higher than the set level in the trial area. The coordinates of a plurality of independent image processing target areas A1 to A3 are automatically set.
Here, the coordinates of the reference region are measured by, for example, measuring the object to be measured whose shape is known in advance (imaging by the camera 20) with the shape measuring device W, and a plurality of light in the obtained captured image. It is calculated based on the positions (coordinates) of the images of the cutting lines Ls1 to Ls3 and stored in the memory of the image processing device 6.
Further, the set level is a luminance level that is recognized as a part of the image of the light section line if the pixel has a higher luminance.

For example, as shown in FIG. 7, the image processing apparatus 6 has the smallest coordinate in the Y-axis direction for the trial area A0 from the position where the coordinate in the Y-axis direction is the smallest to the position where the coordinate becomes the predetermined value y0. While detecting the coordinates of the pixel having the highest luminance and its luminance for each line in the X-axis direction sequentially from the position, it is determined whether or not the detected luminance is equal to or higher than the set level. Further, the image processing device 6 is configured so that the X coordinate of the pixel when the luminance of the highest luminance pixel first becomes equal to or higher than the set level, or the luminance of the highest luminance pixel is continuously set to a predetermined line. According to the average value of the X coordinates of the pixels when the minute (for example, 2 to 3 lines) is equal to or higher than the set level, the X coordinates of the plurality of independent reference regions as a whole are shifted. Are automatically set as the image processing target areas A1 to A3 and stored in a predetermined memory.
For example, in the example shown in FIG. 7, the difference between the X coordinate of a pixel having a luminance equal to or higher than the set level and the X coordinate of the light section line Ls1 obtained by measurement of the calibration object is represented by the reference region. The shift amount from the coordinates to the coordinates of the image processing target areas A1 to A3.
As described above, the coordinates of a plurality of independent reference regions corresponding to the case where the surface height of the tire 1 is a predetermined reference height (known height) are set in advance, and the tire surface shape changes. Pixels of the trial area A0 in which only one specific light cutting line (in the example shown in FIG. 7, the light cutting line Ls1) can be expected to pass through the area even if is large. (That is, a position of a part of the specific one light cutting line), and based on the detected position, a shift from the coordinates of the reference area to the coordinates of the image processing target areas A1 to A3 ( In particular, if the X-axis coordinate shift) is performed, it is possible to avoid the out-of-region state.

As described above, in the measurement of the tire shape using the shape measuring device W, the light projecting device 10 and the camera 20 are provided with a principal ray (center line) of each of a plurality of line lights by a holding mechanism (not shown). In the direction of regular reflection with respect to the surface of the tire 1 so that the field of view of the camera 20 exists. While the light projecting device 10 and the camera 20 are held as described above, the light projecting device 10 irradiates the surface of the tire 1 with a plurality of line lights, and images of the plurality of line lights ( The images of the light cutting lines Ls1 to Ls3) are imaged by the camera 20 at a constant angular period in the rotation of the tire 1 (an example of the line light irradiation / imaging process).
Further, the image processing device 6 (an example of a calculation unit) corresponds to each of the plurality of separated light cutting lines Ls1 to Ls3 in the coordinate system of the captured image of the camera 20 for each of the plurality of captured images obtained by the camera 20. The coordinates of the optical cutting lines Ls1 to Ls3 (the optical cutting line coordinates) are individually detected from each of a plurality of preset image processing target areas A1 to A3 (the optical cutting line coordinate detection step). Example).
Further, the image processing device 6 or the host computer (an example of a calculation unit) determines the tire surface height distribution (one-dimensional distribution) based on the plurality of light cutting line coordinates detected according to the tire rotation angle. Or a two-dimensional distribution) (an example of the surface shape calculation step).

When line light is irradiated on the surface of the black and glossy tire 1, the amount of specularly reflected light is larger than that of scattered reflected light directed in a specific direction (imaging range of the camera). In addition, since the surface of the tire 1 (particularly the sidewall surface) is curved, an image of one line light having a long line length is taken by the camera 20 in the regular reflection direction of the principal ray of the line light. However, the specularly reflected light of the line light that is away from both sides from the principal light does not reach the camera 20.
For example, in FIG. 2, when the length of the line light output from the central line light source 12 is increased, the specularly reflected light near the both ends of the line light is in a direction completely different from the direction of the camera 20. Will head. Therefore, the amount of reflected light that reaches the camera 20 is insufficient for a portion far from the center in the entire line light image, and a clear image cannot be obtained.

On the other hand, the shape measuring device W captures an image of the line light by the camera 20 arranged in the regular reflection direction of the line light irradiated on the surface of the tire 1, so that the intensity of the line light is not increased (high A clear image of the line light irradiated on the surface of the tire 1 even if a line light image is taken at a sufficiently high imaging rate (for example, 4000 frames or more per second) without using a power line light source. Can be obtained. In addition, the plurality of line light sources 11 to 13 irradiate the tire surface with a plurality of line lights having a relatively short line length, and the camera 20 is positioned in the regular reflection direction of the principal ray of each of the plurality of line lights. , A clear image can be obtained for the entire line light image. As a result, the surface shape of the tire 1 can be detected at high speed and with high spatial resolution without causing thermal damage to the tire 1.
The shape measuring device W includes a plurality of sensor units 3 each including a set of the light projecting device 10 (line light irradiating means) and a camera 20. In parallel with each of a plurality of surfaces (front and back sidewall surfaces and tread surfaces), the light projection device 10 irradiates the line light and the camera 20 captures an image of the line light. Thereby, the shape measurement of a plurality of surfaces (sidewall surface and tread surface) of the tire can be performed simultaneously, and the time required for the shape measurement of the entire detection target surface of the tire 1 can be shortened.

By the way, as shown in FIG. 5, the shape measuring apparatus W according to the embodiment of the present invention uses a plurality of line lights irradiated on the surface of the tire 1 by the light projecting apparatus 10 (an example of the line light irradiation means). Can be provided with a collimating lens 30 (corresponding to the collimating means).
Alternatively, as shown in FIG. 6, the shape measuring device W transmits each of a plurality of line lights irradiated on the surface of the tire 1 by the light projecting device 10 (an example of the line light irradiation means) in the line length direction. It is conceivable to provide a condensing lens 40 (corresponding to the condensing means) for condensing light.
By providing the collimating lens 30 or the condensing lens 40, even if the line length of each of the plurality of line lights irradiated on the surface of the curved tire 1 is slightly increased, the principal ray in the line light is directed to both outer sides. The specular reflection direction of the separated light beam can be brought close to the direction of the imaging range of the camera 20. As a result, the number of line lights can be reduced and the apparatus can be simplified.

In the above-described embodiment, the light projecting device 10 including a plurality of light sources (the line light sources 11 to 13) is shown. However, a plurality of light cutting lines Ls1 to Ls3 are formed on the tire surface. Other configurations are also conceivable as a projector for irradiating the line light.
For example, the light projecting device 10 branches one line light source and line light emitted from the line light source into a plurality of line lights, and the plurality of line lights after the branching are separated into a plurality of lines on the tire surface. An embodiment including an optical device that irradiates so that the light cutting lines Ls1 to Ls3 are formed is also conceivable. Thereby, the number of light sources can be reduced.

Further, it is conceivable that the plurality of light projecting devices 10 provided for each inspection target surface of the tire 1 include the line light sources 11 to 13 that output line lights having different wavelengths for each inspection target surface.
In that case, in each of the plurality of sensor units 3, an optical filter that selectively transmits light of a predetermined wavelength output from the light projecting device 10 corresponding to the camera 20 in the optical path of the incident light to the camera 20. Is provided.
For example, the light projecting device 10 in each of the sensor units 3a to 3c outputs line light having wavelengths of 650 nm, 670 nm, and 690 nm, respectively, and the wavelength is 650 ± on the front surface of the camera 20 that captures an image of the line light. It is conceivable to arrange a band-pass filter that selectively transmits light of 5 nm, 670 ± 5 nm, and 690 ± 5 nm.
Thereby, in the shape measurement of a certain surface of the tire 1, it is possible to prevent the line light used on the other surface from becoming noise light.
In addition, the plurality of light projecting devices 10 output line lights of different colors (wavelengths), and the image processing device 6 supports each captured image (color image) of each camera 20 that captures a color image. It is also conceivable to extract an image of the color (wavelength) to be used as an image of line light.

In the above-described embodiment, an example is shown in which shape measurement is performed while the tire rotating machine 2 rotates the tire 1 around the rotation shaft 1g.
However, in a state where the tire 1 itself is fixed, the sensor unit 3 (3a to 3c), which is the whole or a part of the shape measuring device W, rotates around the rotation axis 1g of the tire 1 by a predetermined rotation mechanism. It is possible to make it.
Further, the shape measuring device W is provided with a proximity sensor that detects that the sensor unit 3 (3a to 3c) is closer to the tire 1 than a predetermined distance, and the unit driving device 4 is connected to the proximity sensor. It is desirable to have a function of controlling the sensor unit 3 (3a to 3c) so as not to contact the tire 1 based on the detection result.
Further, the support mechanism of the sensor unit 3 (3a to 3c) supports the sensor unit 3 (3a to 3c) and rotates the tire 1 when a predetermined force or more is applied in the rotation direction of the tire 1. It is preferable to provide an arm having a joint part that bends in the direction or a damper that absorbs the impact.
Thereby, even when the sensor unit 3 contacts the tire 1, it is possible to prevent the device from being damaged.

In the above-described embodiment, the rotating tire 1 is the object to be measured, and the shape measuring device W that measures the surface of the tire that moves by the rotation is shown. It is also possible to measure the shape.
For example, the sensor unit 3 is disposed so as to face one side or both sides of a strip or plate-like rolled material that moves in a linear direction, and the image processing device 6 and the host computer (not shown) perform the above-described implementation. If processing similar to the processing in the form is performed, the surface shape of the rolled material can be measured at high speed and without contact.
Further, as shown in the embodiment, in addition to the device configuration for moving the surface of the object to be measured such as the tire 1 or the rolled material while the sensor unit 3 is fixed, the object to be measured is fixed, An apparatus configuration that moves the sensor unit 3 along the surface of the object to be measured (linear movement or rotational movement) is also conceivable.

  The present invention can be applied to a shape measuring device that measures the surface shape of a tire, a metal member, or the like.

The figure showing the schematic structure of the shape measuring apparatus W which concerns on embodiment of this invention. The figure which represented typically the three-dimensional arrangement | positioning of the light source and camera in a sensor unit with which the shape measuring apparatus W is provided. The figure which represented typically the arrangement | positioning of the line light source and camera in a sensor unit when it sees from a specific direction (Y-axis direction). The figure which represented typically the arrangement | positioning of the line light source and camera in a sensor unit when it sees from the direction perpendicular | vertical to the tire surface of the position where the chief ray of line light arrives. The figure which represented typically a mode that line light was collimated in a sensor unit. The figure which represented typically a mode that line light was condensed in a sensor unit. The figure which represented typically an example of the captured image of the tire with the camera in the shape measuring apparatus W. FIG. The figure which represented typically the distribution of the measurement data obtained by the shape measuring apparatus W, and the mode of data shift. The figure which represented typically an example of the picked-up image of the to-be-measured object for the calibration by the camera in the shape measuring apparatus W. The figure which represented typically a mode that position shift had arisen in these optical cutting lines, when connecting several optical cutting lines on the tire surface and forming one optical cutting line.

Explanation of symbols

W: Shape measuring device 1: Tire 2: Tire rotating machine 3: Sensor unit 4: Unit drive device 5: Encoder 6: Image processing device 10: Projection device 11, 12, 13: Line light source 20: Camera 21: Image sensor 22: Camera lens Ls1, Ls2, Ls3: Optical cutting line

Claims (13)

A shape measuring apparatus for measuring the surface shape of the object to be measured by capturing an image of line light irradiated on the surface of the object to be moved relatively and performing shape detection by a light cutting method based on the captured image Because
By irradiating a plurality of line lights from a direction different from the detected height direction of the surface of the object to be measured, the surface of the object to be measured is orthogonal to the first direction which is the moving direction of the surface of the object to be measured. Line light irradiation means for forming a plurality of separated light cutting lines extending in the second direction and occupying ranges in the second direction are shifted from each other;
Imaging means for capturing images of the plurality of separated light cutting lines formed on the surface of the object to be measured in a direction in which principal rays of the plurality of line lights are regularly reflected on the surface of the object to be measured. When,
For each of a plurality of captured images obtained by the imaging unit in response to the movement in a certain unit, a plurality of preset values corresponding to the plurality of separated light cutting lines in the coordinate system of the captured image of the imaging unit A light cutting line coordinate detection means for individually detecting a light cutting line coordinate which is a coordinate of the image of the light cutting line from each of the images of the independent image processing target areas;
Surface shape calculating means for calculating a surface height distribution in the first direction of the object to be measured based on a plurality of the light cutting line coordinates detected by the light cutting line coordinate detecting means;
A shape measuring apparatus comprising:   2. A set of a plurality of sets of the line light irradiating means and the imaging means for irradiating the line light and capturing an image of the line light in parallel on each of a plurality of surfaces of the object to be measured. The shape measuring device described in 1.   The shape measuring apparatus according to claim 2, wherein the plurality of line light irradiation units corresponding to the plurality of surfaces of the object to be measured output the line light having different wavelengths.   The shape measuring apparatus according to claim 1, further comprising collimating means for collimating each of the plurality of line lights irradiated on the surface of the object to be measured by the line light irradiating means in the line length direction. .   The shape according to any one of claims 1 to 3, further comprising condensing means for condensing each of a plurality of line lights irradiated on the surface of the measurement object in the line length direction by the line light irradiation means. measuring device.   The line light irradiating means forms the plurality of separated light cutting lines in which the positions of the end portions in the second direction of the adjacent objects in the second direction overlap each other on the surface of the object to be measured. The shape measuring apparatus according to claim 1.   The light cutting line coordinate detecting means detects the light cutting line coordinates by detecting the coordinates of the highest luminance pixel for each line in the first direction for each of the images of the plurality of independent image processing target areas. The shape measuring apparatus according to any one of claims 1 to 6. Detecting a position of a pixel having a luminance of a predetermined level or more in one or a plurality of predetermined trial areas in a captured image obtained by imaging the object to be measured by the imaging means ;
Shifting the coordinates of a plurality of predetermined independent reference areas in a captured image obtained by imaging the object to be calibrated by the imaging means according to the detection position of a pixel having a luminance of the predetermined level or higher. The shape measuring apparatus according to claim 1, further comprising an image processing target area automatic setting unit that automatically sets the coordinates of the plurality of independent image processing target areas.   The surface shape calculating means corresponds to the movement in the first direction between the plurality of light cutting line coordinates detected by the light cutting line coordinate detection means and the plurality of separated light cutting line coordinates in the first direction. The surface height distribution in the first direction and the second direction of the object to be measured is calculated based on set shift information set in advance with respect to the shift amount. The shape measuring apparatus described.   The shape measuring apparatus according to claim 1, wherein the object to be measured is a rotating tire. The line light irradiation means includes first line light irradiation means for forming the plurality of separated light cutting lines extending in the second direction substantially parallel to a radial direction of the tire on a sidewall surface of the tire. ,
11. The image pickup means comprises first image pickup means for picking up images of the plurality of separated light cutting lines formed on a sidewall surface of the tire by the first line light irradiation means. The shape measuring device described in 1. Second line light irradiation means for forming the plurality of separated light cutting lines extending in the second direction substantially parallel to a direction orthogonal to the circumferential direction of the tire on the tread surface of the tire. Comprising
11. The image pickup device according to claim 10, wherein the image pickup device includes a second image pickup device that picks up images of the plurality of separated light cutting lines formed on the tread surface of the tire by the second line light irradiation device. The shape measuring apparatus described. A shape measuring method for detecting the surface shape of the object to be measured by capturing an image of line light irradiated on the surface of the object to be measured that moves relatively, and performing shape detection by a light cutting method based on the captured image Because
By irradiating a plurality of line lights from a direction different from the detected height direction of the surface of the object to be measured, the surface of the object to be measured is orthogonal to a first direction which is a moving direction of the surface of the object to be measured. Line light irradiation means for forming a plurality of separated light cutting lines extending in the second direction and occupying ranges in the second direction, and the plurality of separations formed on the surface of the object to be measured The image pickup means for picking up the image of the light cutting line is arranged such that the field of view of the image pickup means is positioned in a direction in which the light along the principal ray of each of the plurality of line lights is regularly reflected with respect to the surface of the object to be measured. In this state, the line light irradiating means irradiates the surface of the object to be measured with the plurality of line lights, and images the plurality of separated light cutting lines according to the movement in a certain unit. Imaging by means A line light irradiation, an imaging step that,
The plurality of captured images obtained by the line light irradiation / imaging process are set in advance by a predetermined calculation unit corresponding to the plurality of separated light cutting lines in the coordinate system of the captured image of the imaging unit. A light cutting line coordinate detection step for individually detecting a light cutting line coordinate which is a coordinate of the image of the light cutting line from each of the images of the plurality of independent image processing target areas;
A surface shape calculating step of calculating a surface height distribution of the object to be measured based on the plurality of light cutting line coordinates detected by the light cutting line coordinate detecting step by a predetermined computing means;
The shape measuring method characterized by performing.

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