DE102010060852B4 - Apparatus and method for detecting a surface texture of a surface of a workpiece - Google Patents

Abstract

Device for detecting a surface structure of a surface (1, 5, 6) of a workpiece (10), in particular a cylinder bore (1) or a piston (5) of an internal combustion engine, comprising an optical sensor (2, 2) for detecting a photodiode line a surface image of the workpiece (10), the longitudinal axis of which extends in a longitudinal direction, and a lighting means for illuminating the surface (1, 5, 6) and with a sensor positioning and adjusting device for positioning and adjustment of the sensor (2 2) relative to the surface of the workpiece, characterized in that the array of photodiodes belongs to a CI sensor in which the photodiode array is preceded by a CI optic towards the surface of the workpiece, and in that the sensor positioning and Adjusting means comprises a sensor rotating means, by means of which the optical sensor (2, 2) erstr such a parallel to the longitudinal axis of the CI sensor pivoting rotation axis is rotatable, that by the rotation, the angular orientation (4, 4) of the CI sensor relative to the surface (1, 5; 6) of the workpiece (10) is changeable.

Description

The invention relates to an apparatus and a method for detecting a surface structure of a, in particular cylindrical, surface of a workpiece, in particular a cylinder bore or a piston of an internal combustion engine, with an optical sensor which contains a diode array camera or a photodiode array for detecting a surface image of the workpiece, whose longitudinal axis extends in a longitudinal direction and with a lighting means for illuminating the surface and with a sensor positioning and -Justiereinrichtung for positioning and adjustment of the sensor relative to the surface of the workpiece. Specifically, the invention also relates to a mounting and adjustment device for surface scanners.

In order to capture the surface structure of functional treads, in particular of cylinders and pistons, they can be photographically recorded. Since these are comparatively large surfaces, it is advantageously possible to use a row of photodiodes, preferably with a superior optics, so-called "CIS elements". Within the scope of this property right, a "photodiode line" is also a "diode line camera". Similar to an office scanner, the photodiode line can be guided past the surface to be tested at a constant distance. This can in a workpiece with a cylindrical inner surface, ie z. Example, in a tubular workpiece, in particular in a cylinder bore, done on a circular path, while in a workpiece with a cylindrical outer surface, for example in a piston, meaningful way the photodiode line is stationary and the workpiece is rotated in front. With a flat workpiece surface, it will be preferred to move it linearly relative to the optical sensor.

From the DE 697 03 487 T2 and the DE 195 11 534 A1 Devices have become known which, by means of a scanning operation by means of a color line scanning camera or color line camera, provide three-dimensional (3D) images of surfaces for detecting 3D defects in an automatic inspection or inspection of surfaces, wherein the image data supplied by means of mathematical methods be evaluated mathematically. Such devices are relatively expensive and expensive.

From the DE 197 04 750 A1 a device has become known according to the preamble of claim 1, which additionally comprises a sensor rotating device with which a sensor having a photodiode array is rotatable about an axis parallel to the longitudinal axis of the array of photodiodes.

From the DE 29 30 407 A1 For example, a device with a sensor for optically detecting the surface structure of a cylinder bore with rotation possibilities for the optical sensor has become known.

From the US 2002/0186368 A1 For example, a device with CI sensors has become known which can be used not only in office document scanners but also for detecting the surface structure of a workpiece.

It is an object of the invention to provide an improved apparatus and method of the type mentioned above.

This object is solved by the features of claims 1 and 7.

The inventive device is characterized by a compact design, flexibility in use, ease of use and a functional structure, is particularly easy to implement and can be based essentially or wholly on commercially available components. It serves to position an optical image acquisition system for preferably cylindrical workpieces.

Depending on the reflection properties of the surface to be tested, specularly reflective or light-scattering, the line of photodiodes or the optics in front can be oriented in order to be able to record the surface with the greatest possible contrast. Furthermore, the camera or the photodiode array, if necessary also the recording optics, can be guided at a defined distance from the surface, so that the image is in focus. The illumination may be designed as a rod-shaped element, for example as a fluorescent tube or as light-emitting diodes arranged in series. The lighting can be oriented so that depending on the task either receives a maximum contrast, z. B. by a grazing light, or a high brightness. All these settings are not available in an office scanner or fax machine, which is why it z. B. can not reflect well reflective surfaces.

When testing devices are used in production, the workpiece types change at rather larger time intervals, so that a manual readjustment is tolerable if you want to switch to another type of workpiece. The industry will prefer to ask for adjustable test equipment, so that a flexible use with different types of workpieces is possible. It is therefore useful and economical, for automated visual inspection of surfaces to keep those device components adjustable, their optimal function of a pertinent spatial orientation depends. This avoids the procurement of several workpiece-specific test devices.

In particular, the following adjustment possibilities, be they manually or motor-adjustable, are helpful: positioning of the photodiode array or the sensor in the axial direction and / or in the radial direction for focusing and / or rotation of the sensor for adjusting the angle of the light receiving direction to the object surface.

It is also advantageous if non-mechanical variables such as the illuminance and / or the exposure time and / or the travel or scanning speed are adjustable. The lighting means, in particular the light source (s), can be arranged together in a photodiode housing or separately. The presence of a plurality of illumination means or light sources may prove helpful in some workpiece surfaces for better illumination or contrast enhancement. These illumination means or light sources can then be differently aligned with respect to the surface to be tested.

The setting of measurement parameters such as the illumination intensity and / or the exposure time and / or the travel or scanning speed can advantageously be computer-assisted or by means of software depending on the local surface reflectivity, the surface light scattering behavior, the degree of contamination (carbonization) or of smooth spots, z. B. by querying / evaluating the sensor signals or an additional existing monitor sensor. Local means advantageous both depending on the rotation angle as well as dependent on the y-direction ( 2 ).

According to an advantageous embodiment, it can be provided that the sensor contains the illumination means and / or that the sensor contains a lens that is superior to the illumination means in the direction of the surface of the workpiece to be tested.

According to a preferred refinement, it can be provided that the sensor positioning and adjusting device has a distance adjusting means for setting different distances of the optical sensor relative to the surface of the workpiece and / or an axial positioning means for setting different axial positions of the optical sensor along the axis of rotation or relative to the surface of the workpiece and / or a radial positioning means for adjusting different radial positions of the optical sensor relative to a curved or cylindrical surface of the workpiece.

In another illustration of the invention, the device mentioned at the outset and the method mentioned at the outset may be characterized in that all relevant mechanical settings for obtaining optimal measurement data for a given workpiece can be made manually or by motor means.

Advantageously, the sensor or the photodiode array for recording an image of the surface to be tested of a tubular workpiece to rotate about its longitudinal axis.

According to an advantageous development of the device according to the invention, it can be provided that it additionally contains a distance measuring means for measuring the distance of the optical sensor from the surface of the workpiece or for measuring a profile depth of surface structures of the surface of the workpiece. Advantageously, means may be provided to detect such distance measured values or the profile depth measured values and / or brightness contrast values.

It may be of particular advantage if at least two, preferably similar, optical sensors, in particular at least two rows of photodiodes, are provided for detecting the surface structure of the surface of the workpiece and / or at least two illumination means for illuminating the workpiece. In particular, more than one CI sensor and / or more than one light source may be present.

According to a particularly preferred embodiment it can be provided that the at least two optical sensors and / or the at least two illumination means with the aid of the sensor rotating means or by means of such a sensor rotating device, preferably independently and / or, in particular different, relative to each other , about which or about a respective axis of rotation extending parallel to the longitudinal axis of the row of photodiodes or of the respective rows of photodiodes are rotatable or rotated.

Useful is an additional detection of the z-coordinate ( 1 ) of a pixel so as to obtain a 3D surface image by scanning the workpiece surface. This can be z. B. measure the depth of pores. This can be achieved, for example, by attaching two rows of photodiodes including optics and lighting at a suitable distance and orientation to the surface. During the relative movement between the sensor and the surface, each object point is thus seen from two different directions, and the stereo image formed therefrom can be evaluated. This effect can be enhanced by using different colored light for each of the Viewing directions. Preferably, a three-dimensional (3D) image of the surface of the workpiece can be calculated from the signals or image data of the at least two optical sensors.

Alternatively or additionally, you can also tilt the optical sensor, z. B. by means of an actuator, so that the sensor "looks" at two consecutive scans from different directions on the same object point. The two image files can be, if necessary, after a suitable reorientation, z. B. by correlation method, then charge to a stereo file.

In other words, with the aid of the CI sensor, a first image of the surface of the workpiece can be detected in a first rotational position of the sensor rotating device, whereupon a second rotational position of the sensor rotating device is changed with the aid of the same CI sensor in a second rotational position of the sensor rotating device Image of the surface of the workpiece can be detected, that is, in a different angle setting or angular orientation relative to the workpiece surface, whereupon from the first image and from the second image, preferably after a lateral correlation, a three-dimensional (3D) image of the surface of the workpiece calculated can be.

Likewise, one can "look" perpendicular to the surface to be tested with the optical sensor and can illuminate this surface successively from two or more different directions. From the different shadow images the surface contour can be reconstructed. In this regard, reference may be made, for example, to the article by Vasileios Argyriou and Maria Petru, "Photometric Stereo: An Overview", in the Advances magazine in Imaging and Electron Physics, Vol. 156, pp. 1-54, 2009.

In other words, a first image of the surface of the workpiece can be detected with the aid of the CI sensor in a first rotational position of the sensor rotating device at a first rotational position of the illumination means, whereupon with the aid of the same CI sensor in the first rotational position or in a second rotational position a second image of the surface of the workpiece are detected under a second rotational position of the same and / or another illumination means, whereupon from the first image and from the second image a three-dimensional (3D) image or a three-dimensional (3D) surface topography of the Surface of the workpiece can be calculated. If, for example, one subtracts the two image data or files thus obtained, then only those image parts result for which the z coordinate is not equal to zero. Alternatively or equivalently, the summation of two dark field illumination images would be possible, which have been recorded from different illumination directions.

It is understood that the above measures can be combined with one another as far as feasibility is concerned.

Further advantages, features and aspects of the invention will become apparent from the claims and from the following description part, in which a preferred embodiment of the invention with reference to the figures.

Show it:

1 a schematic cross-section of a device according to the invention with two relative to each other and relative to a surface to be tested two cylindrical workpieces in their angular position rotatably adjustable optical sensors;

2 the device according to the invention 1 in a schematic longitudinal section.

The device shown in the figures serves to detect a surface structure of a cylindrical surface 1 . 5 ; 6 a workpiece 1 . 5 Here, for purposes of illustration, both a workpiece with a bore or tube inner wall 1 as well as a workpiece with a cylinder or tube outer wall 5 are shown. The device shown in the figures comprises two optical sensors 2 . 2 , each one a photodiode line 2 for detecting a surface image of the workpiece 1 . 5 and also each contain a lighting means, which are each arranged in a common housing. Every photodiode line 2 . 2 So serves as a line or line scan camera to capture a surface image of the workpiece 1 . 5 , The two rows of photodiodes and lights 2 . 2 are each arranged parallel to each other and are each on a parallel to the respective longitudinal axis of the respective photodiode array in the longitudinal direction extending sensor holding means, preferably a sensor holding rail 11 , Fixed, the or on a transversely, preferably perpendicular, extending carrier, preferably a boom 9 , are attached. The carrier or boom 9 is on a shaft or axis of rotation 8th an engine 7 attached. With the help of the rotary motor 7 So can the two optical sensors 2 . 2 together around the axis of rotation 8th be rotated so as to take an image or a scan along the bore inner wall 1 in a preferably constant distance to the surface 6 the bore interior wall 1 to be turned. For inspection of the surface 6 the cylindrical outer wall of in 1 On the left indicated cylinder body this can by means not shown in the figures rotating means, preferably by means of a motor, relative to the preferably stationary permanent sensors 2 . 2 to be rotated.

For fine adjustment of the respective optical sensor 2 . 2 relative to the surface 6 the bore inner wall 1 or relative to the surface 6 the cylinder outer wall 5 is every photo sensor 2 . 2 via a displacement device 3 with the respective sensor holding means 11 coupled, with the aid of the respective displacement device 3 . 3 the respective optical sensor 2 . 2 in the radial direction relative to the surface to be tested 6 can be moved.

Every optical sensor 2 . 2 can according to the invention by means of a sensor rotating device to a parallel to the longitudinal axis of the respective photodiode array 2 . 2 extending axis of rotation, preferably the longitudinal axis of the respective sensor retaining rail 11 , At least over a certain rotation angle range, are rotated, so that upon rotation of the respective Fotodiodenzeile 2 . 2 about the said axis of rotation, the angular orientation or angle adjustment 4 the respective photodiode line 2 . 2 relative to the surface to be tested 6 changed. A corresponding angle setting 4 . 4 can be done manually or preferably by motor, by a motor or by several motors, which are not shown in the figures.

The respective optical sensor 2 . 2 is with the respective sensor holding means 11 via a Höhenjustiermittel, preferably a Höhenjustierlagerung 12 , Connected, with the help of a height adjustment of the respective optical sensor 2 . 2 relative to the respective sensor holding means 11 or relative to the surface to be tested 6 can be made. This height adjustment can also be done manually or preferably by motor with the help of one or more motors not shown in the figures.

The device according to the invention can be coupled to an evaluation unit, not shown in the figures, by means of which the signals or image data of the rows of photodiodes can be coupled 2 . 2 can be evaluated using mathematical methods. In the exemplary embodiment shown in the figures, a three-dimensional (3D) stereo image of the surface can be obtained from the signals or image data of the two rows of photodiodes with the aid of the evaluation unit 1 . 5 of the workpiece 10 be calculated.

Alternatively or additionally, using any type of photodiode 2 the two rows of photodiodes 2 . 2 in a first rotational position of the sensor rotating device, a first image of the surface 6 of the workpiece 1 . 5 ; 10 what to do with the help of the same line of photodiodes 2 in a relation to the first rotational position changed second rotational position of the sensor rotating device, a second image of the surface 6 of the workpiece 1 . 5 ; 10 are detected, and wherein or from what from the first image and from the second image with the aid of the evaluation unit, a three-dimensional (3D) stereo image of the surface 1 . 5 of the workpiece 10 can be calculated.

Alternatively, or in addition to the above measures, using any type of photodiode 2 the two rows of photodiodes 2 . 2 in a first rotational position of the sensor rotating means under a first adjustment of the illumination means, a first image of the surface 6 of the workpiece 1 . 5 ; 10 what to do with the help of the same line of photodiodes 2 in a second rotational position of the sensor rotating device under a second rotational position of the same illumination means, a second image of the surface 6 of the workpiece 1 . 5 ; 10 can be detected, and wherein or from the first image and from the second image, a three-dimensional (3D) stereo image or a three-dimensional (3D) surface topography of the surface 1 . 5 of the workpiece 10 can be calculated with the help of the evaluation unit.

LIST OF REFERENCE NUMBERS

1

Surface / wall bore / pipe inner wall / cylinder bore / workpiece

2

optical sensor / photodiode array (and illumination)

3

Radial positioning / Radial displacement direction

4

angle adjustment

5

Surface / cylinder / pipe outer wall / piston

6

Scanning area / surface / workpiece

7

(Rotary) motor

8th

axis of rotation

9

boom

10

Workpiece (wall)

11

Sensor holding means / sensor retaining rail

12

Höhenjustiermittel / axial positioning / Höhenjustierlagerung

Claims (9)

Device for detecting a surface structure of a surface ( 1 . 5 ; 6 ) of a workpiece ( 10 ), in particular a cylinder bore ( 1 ) or a piston ( 5 ) of an internal combustion engine, with an optical sensor ( 2 . 2 ) comprising a photodiode line for capturing a surface image of the workpiece ( 10 ), whose longitudinal axis extends in a longitudinal direction, and with a lighting means for illuminating the surface ( 1 . 5 ; 6 ) and with a sensor positioning and adjusting device for positioning and adjusting the sensor ( 2 . 2 ) relative to the surface of the workpiece, characterized in that the row of photodiodes belongs to a CI sensor in which the Is arranged in the direction of the surface of the workpiece, a CI optics, and that the sensor positioning and -Justiereinrichtung comprises a sensor rotator, by means of which the optical sensor ( 2 . 2 ) is rotatable about an axis of rotation extending parallel to the longitudinal axis of the CI sensor such that the angular orientation ( 4 . 4 ) of the CI sensor relative to the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ) is changeable. Device according to claim 1, characterized in that the sensor ( 2 . 2 ) contains the illumination means and / or that the sensor ( 2 . 2 ) a the illumination means towards the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ) contains superior optics. Apparatus according to claim 1 or 2, characterized in that the sensor positioning and -Justiereinrichtung a Abstandseinstellmittel for setting different distances of the optical sensor ( 2 . 2 ) relative to the surface ( 1 . 5 ) of the workpiece ( 10 ) and / or an axial positioning means ( 12 ) for adjusting different axial positions of the optical sensor ( 2 . 2 ) along the axis of rotation and / or a radial positioning means ( 3 . 3 ) for setting different radial positions of the optical sensor ( 2 . 2 ) relative to a curved or cylindrical surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ) contains. Device according to one of claims 1 to 3, characterized in that it additionally contains a distance measuring means for measuring the distance of the optical sensor from the surface of the workpiece or for measuring a profile depth of surface structures of the surface of the workpiece. Device according to one of claims 1 to 4, characterized in that these at least two, preferably similar, optical sensors ( 2 . 2 ), in particular at least two rows of photodiodes, for detecting the surface structure of the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ) and / or at least two illumination means for illuminating the workpiece ( 10 ). Apparatus according to claim 5, characterized in that the at least two optical sensors ( 2 . 2 ) and / or the at least two illumination means by means of the sensor rotator or by means of a respective sensor rotator, preferably independently of each other and / or relative to each other, about or one parallel to the longitudinal axis of the photodiode array or the respective Photodiode line extending axis of rotation are rotatable. Method for detecting a surface structure of a surface ( 1 . 5 ; 6 ) of a workpiece ( 10 ), in particular a cylinder bore ( 1 ) or a piston ( 5 ) of an internal combustion engine, by means of a device according to one of claims 1 to 6, characterized in that the optical sensor ( 2 . 2 ) is rotated about the axis of rotation by means of the sensor-rotating device, so that the angular orientation of the CI sensor relative to the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ) changes. A method according to claim 7, characterized in that with the aid of the CI sensor in a first rotational position of the sensor rotating means a first image of the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ), whereupon, with the aid of the same CI sensor, in a second rotational position of the sensor rotating device which is changed with respect to the first rotational position, a second image of the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ), whereupon from the first image and from the second image a three-dimensional (3D) image of the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ) is calculated. A method according to claim 7 or 8, characterized in that with the aid of the CI sensor in a first rotational position of the sensor rotating means at a first rotational position of the illumination means, a first image of the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ) is detected, whereupon, with the aid of the same CI sensor in a second rotational position of the sensor rotating device under a second rotational position of the same illumination means, a second image of the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ), whereupon from the first image and from the second image a three-dimensional (3D) image or a three-dimensional (3D) surface topography of the surface ( 1 . 5 ; 6 ) of the workpiece ( 10 ) is calculated.

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