U.S. patent application number 14/871646 was filed with the patent office on 2016-06-30 for bore testing device.
The applicant listed for this patent is JENOPTIK Industrial Metrology Germany GmbH. Invention is credited to Michael RUDOLF.
Application Number | 20160187265 14/871646 |
Document ID | / |
Family ID | 55531013 |
Filed Date | 2016-06-30 |
United States Patent
Application |
20160187265 |
Kind Code |
A1 |
RUDOLF; Michael |
June 30, 2016 |
Bore Testing Device
Abstract
A bore testing device for testing the inner surface of a bore in
a workpiece is described. The bore testing device has a measuring
head which defines an axial direction, and on which axial direction
an optical system is situated which is in image transmission
connection with a digital image sensor and a downstream evaluation
apparatus. An apparatus for determining surface depth information
from the output signals of the digital image sensor is
provided.
Inventors: |
RUDOLF; Michael; (Konstanz,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JENOPTIK Industrial Metrology Germany GmbH |
Villingen-Schwenningen |
|
DE |
|
|
Family ID: |
55531013 |
Appl. No.: |
14/871646 |
Filed: |
September 30, 2015 |
Current U.S.
Class: |
356/496 ;
356/626 |
Current CPC
Class: |
H04N 2005/2255 20130101;
G01B 9/0209 20130101; H04N 5/2256 20130101; G01N 21/954 20130101;
G01B 11/12 20130101; H04N 9/07 20130101; G01B 9/02021 20130101;
A61B 1/04 20130101; A61B 1/06 20130101; G01N 2021/9544 20130101;
G01B 11/2441 20130101; H04N 5/23238 20130101; G01B 11/22 20130101;
G01B 9/02 20130101 |
International
Class: |
G01N 21/954 20060101
G01N021/954; G01B 9/02 20060101 G01B009/02; G01B 11/22 20060101
G01B011/22 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 1, 2014 |
DE |
10 2014 114 304.3 |
Dec 16, 2014 |
DE |
10 2014 118 753.9 |
Claims
1. A testing device for testing the inner surface of a bore in a
workpiece, comprising: a) a measuring head which defines an axial
direction, and on which an optical system with a panoramic view is
situated which is in image transmission connection with a digital
image sensor and a downstream digital evaluation apparatus; and b)
an apparatus for determining surface depth information from the
output signals of the digital image sensor.
2. Testing device according to claim 1, wherein: a) the apparatus
for determining surface depth information includes a white light
interferometer having a light source whose light is one of
coupleable and coupled into the beam path of the optical system for
striking the inner surface.
3. Testing device according to claim 2, wherein: a) a positioning
apparatus is associated with a reference mirror of the white light
interferometer, the positioning apparatus being controllable by a
control apparatus which is in data transmission connection with the
evaluation apparatus in such a way that the evaluation apparatus
assigns the associated output signals of the digital image sensor
to different positions of the reference mirror.
4. Testing device according to claim 1, wherein: a) an advancing
apparatus for advancing the measuring head in the axial direction
in one of a stepwise and a continuous manner is associated with the
measuring head.
5. Testing device according to claim 1, wherein: a) one of: i) the
measuring head; and, ii) the measuring head together with an
illumination arrangement is configured as an endoscope which is
insertable into the cavity to be tested.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of German application
No. DE 10 2014 114 304.3, filed Oct. 1, 2014, and this application
claims priority of German application No. DE 10 2014 118 753.9,
filed 18 Dec. 2014, and each of which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The invention relates to a bore testing device for testing
the inner surface of a bore in a workpiece.
BACKGROUND OF THE INVENTION
[0003] Bore testing devices of this type, also referred to as
internal test sensors, are used to test the inner surfaces of
bores, for bores, for example in the inspection of cylinder bores
in crankcases. They are used for imaging the radial inner surface
of the bore, and to check whether it meets predetermined
requirements regarding surface quality.
[0004] Such devices are known from WO 2009/003692, DE 4416493 A1,
DE 4320845 C1, and DE 3232904 C2, for example.
[0005] A bore testing device of this type for testing the inner
surface of a bore in a workpiece is known from DE 10 2009 019 459
B4, having a measuring head which defines an axial direction, and
on which an optical system with a panoramic view is situated which
is in image transmission connection with a digital image sensor and
a downstream evaluation apparatus. The testing device known from
the cited publication also has an illumination arrangement for
illuminating an imaging area of the inner surface which is detected
by the optical system. The testing device known from the cited
publication allows quick, accurate testing of inner surfaces of
cavities, for example bores.
OBJECTS AND SUMMARY OF THE INVENTION
[0006] An object of the invention is to provide a bore testing
device of the type for testing the inner surface of a bore in a
workpiece which is improved with regard to the detection of surface
defects in a bore in a workpiece.
[0007] This object is achieved by the invention set forth
herein.
[0008] This object is achieved by the invention set forth herein
which includes a testing device for testing the inner surface of a
bore in a workpiece having a measuring head which defines an axial
direction, and on which an optical system with a panoramic view is
situated which is in image transmission connection with a digital
image sensor and a downstream digital evaluation apparatus, as well
as an apparatus for determining surface depth information from the
output signals of the digital image sensor.
[0009] The invention provides an apparatus for determining surface
depth information from the output signals of the digital image
sensor. In this way, by means of the testing device according to
the invention it is possible not only to image the inner surface of
the cavity and test it by evaluating the resulting brightness
image, but also to determine its topography. During the testing, if
an anomaly is discovered on the inner surface in the evaluation of
an image (camera image) recorded by the digital image sensor, by
evaluating the output signal of the apparatus for determining
surface depth information it may be concluded whether the detected
anomaly is a depression in the surface, and therefore a
manufacturing defect, or whether it is an elevation caused by
soiling which may possibly be easy to remove.
[0010] In this manner, due to the additional surface depth
information obtained, the test result obtained by means of a bore
testing device according to the invention is much more meaningful
than in testing devices which provide only imaging (brightness
image) of the inner surface, without surface depth information. As
a result, the detection of surface defects is improved. The
apparatus for determining surface depth information from the output
signals of the digital image sensor may have any suitable design,
depending on the particular requirements. Thus, for example, it is
possible to determine the topography of the surface to be examined
based on shadow images, and thus obtain surface depth information,
according to the known "shape from shading" method. However, any
other measuring methods which operate in a contactless manner, in
particular optical measuring methods such as confocal microscopy,
which are suitable for measuring lengths or distances may be
used.
[0011] In this regard, one advantageous further embodiment of the
invention provides that the apparatus for determining surface depth
information includes a white light interferometer, whose white
light is coupleable or coupled into the beam path of the optical
system for striking the inner surface to be examined. Such white
light interferometers, whose design and function per se are
generally known to those skilled in the art, may be used with high
accuracy for determining surface depth information in the context
of the invention. They are relatively simple in design and robust,
and have a high level of measuring accuracy. In the context of the
invention, the mode of action of a white light interferometer is
that the white light of a light source is coupled into the beam
path and split into a reference beam and a measuring beam by means
of a beam splitter, the reference beam being reflected from a
reference mirror, and the measuring beam being reflected from the
surface of the measured object and scattered. The returning beams
are relayed by the beam splitter to the digital image sensor, and
form an interference signal for each individual pixel of the
digital image sensor as a function of the topography of the inner
surface. Each pixel of the digital image sensor scans this
interference signal in the form of a white light correlogram when
the length of the reference arm or the measuring arm of the white
light interferometer is changed by means of a positioning unit. The
interference signal of a pixel then has a maximum modulation when
the optical wavelength of the light striking the pixel is exactly
the same for the reference beam and for the measuring beam. The z
value of a point on the inner surface to be tested, which is imaged
on this pixel of the image sensor, thus corresponds to the z value
of a positioning apparatus for positioning the reference mirror
when the modulation of the correlogram is at a maximum. The surface
depth information, and thus the topography, of the examined surface
may then be ascertained by determining for each individual pixel
the z value of the positioning apparatus for which the modulation
of the output signal of this pixel is at a maximum. This embodiment
thus allows surface depth information to be determined in a
relatively simple manner.
[0012] To achieve a design, e.g., a setup, in a simple and
cost-effective manner in the above-mentioned embodiment, one
advantageous further embodiment of the invention provides that a
positioning apparatus is associated with a reference mirror of the
white light interferometer, the positioning apparatus being
controllable by a control apparatus which is in data transmission
connection with the evaluation apparatus in such a way that the
evaluation apparatus assigns associated output signals of the
digital image sensor to different positions of the reference
mirror. The modulation of the interference signal of a pixel is
thus changed by positioning the reference mirror with the aid of
the positioning apparatus. A high level of measuring accuracy may
thus be achieved by using a positioning apparatus having high
positioning accuracy.
[0013] In other respects, the design and function of a white light
interferometer are generally known to those skilled in the art, and
therefore are not explained here in greater detail.
[0014] By the use according to the invention of an optical system
(imaging optics) with a panoramic view, the inner surface of the
cavity is imaged on the digital image sensor along a
circumferential lateral surface line. In order to examine different
axial areas of the cavity, one advantageous further embodiment of
the invention provides that an advancing apparatus for advancing
the measuring head in the axial direction in a stepwise or
continuous manner is associated with the measuring head.
[0015] Another further embodiment of the invention provides that at
least the measuring head, preferably the measuring head together
with an illumination arrangement for illuminating the inner
surface, is designed as an endoscope which is insertable into the
bore to be tested.
[0016] In the context of the invention, a bore is understood to
mean any rotationally symmetrical or substantially rotationally
symmetrical recess in a workpiece, regardless of how the recess has
been introduced into the workpiece, for example by drilling or by
means of some other machining process, or by molding or the like.
In the context of the invention, a substantially rotationally
symmetrical recess is understood to mean that the basic shape of
the recess is rotationally symmetrical, but may contain grooves or
the like, for example. Within the meaning of the invention, a
rotationally symmetrical recess is of course understood to mean a
recess whose basic shape deviates from rotational symmetry due to
anomalies.
[0017] The invention is explained in greater detail below with
reference to the appended drawing, in which one embodiment of a
bore testing device according to the invention is illustrated in a
highly schematic manner. All features, alone or in any arbitrary
combination, which are described, illustrated in the drawing, and
claimed in the patent claims constitute the subject matter of the
present invention, regardless of their recapitulation in the patent
claims or their back-reference.
[0018] Relative terms such as left, right, up, and down are for
convenience only and are not intended to be limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The sole FIGURE is a schematic side view of an embodiment of
a bore testing device according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The single FIGURE of the drawing illustrates in a highly
schematic manner a side view of one embodiment of a bore testing
device 2 according to the invention for testing the inner surface 4
of a bore 6 in a workpiece 8 (bore inspection device), having a
measuring head 10 which defines an axial direction. The
corresponding axis is symbolized in the figure by a dash-dotted
line 12, and coincides with the optical axis of an optical system
14 (imaging optics) with a panoramic view of 360.degree., situated
on the measuring head 10. The optical system 14 is in image
transmission connection with a digital image sensor 16 and a
downstream digital evaluation apparatus. The evaluation apparatus
has been omitted in the drawing for reasons of simplicity.
[0021] By means of the optical system 14 with a panoramic view, the
inner surface 4 of the bore 6 is imaged on the digital image sensor
16 along a circumferential lateral surface line 16 in the
peripheral direction. The resulting output signal of the digital
image sensor 16 is examined for anomalies or defects of the surface
4 in the downstream digital evaluation apparatus. The basic mode of
functioning of such a bore testing device is generally known to
those skilled in the art, and therefore is not explained here in
greater detail. In this regard, reference is made in particular to
DE 10 2009 019 459 B4.
[0022] To illuminate the inner surface 4, an additional
illumination arrangement may be provided, depending on the
particular circumstances; this additional illumination arrangement
has been omitted in the drawing for reasons of simplicity.
[0023] To position the measuring head 10 relative to the inner wall
4 in the axial direction, an advancing apparatus (symbolized by a
double arrow 18 in the drawing) for advancing the measuring head 10
in a stepwise or continuous manner in the direction of the axis 12
is associated with the measuring head 10. According to the
invention, the bore testing device 2 has an apparatus for
determining surface depth information from the output signals of
the digital image sensor 16, in the illustrated embodiment this
apparatus for determining surface depth information includes a
white light interferometer 20 having a broadband light source
22.
[0024] The beam 24 of the light source 22 is split into a measuring
beam 28 and a reference beam 30 by means of a beam splitter mirror
26. The measuring beam 28 is coupled into the beam path of the
optical system 14 and strikes the inner surface 4. The reference
beam 30 is deflected onto a reference mirror 32, which in the
illustrated embodiment takes place via a deflection mirror 34,
which, however, is not necessary for the basic functioning of the
white light interferometer, and is provided in the illustrated
embodiment solely for structural reasons.
[0025] A positioning apparatus, which is symbolized by a double
arrow 36 in the drawing and is used for changing the length of the
reference beam by linear positioning of the reference mirror 32, is
associated with the reference mirror 32. The reference beam
reflected from the reference mirror 32 is deflected onto the image
sensor 16 via the beam splitter 26. The measuring beam 24 strikes
the inner surface 4, is reflected by same, and likewise reaches the
image sensor 16 via the optical system 14.
[0026] An interference thus results on each pixel of the image
sensor 16 when the optical wavelengths of the measuring beam 24 and
of the reference beam 30 are virtually identical. Each pixel of the
image sensor 16 scans a white light correlogram (interference
signal) when the position of the reference mirror 32, and thus the
optical wavelength of the reference arm of the white light
interferometer 20, is changed by means of the positioning unit 36.
In other respects, the functioning of a white light interferometer
is generally known to those skilled in the art, and therefore is
not explained here in greater detail. In the test position of the
measuring head 10, its axial device corresponds to the axial
direction of the bore 6. The bore testing device 2 according to the
invention functions as follows:
[0027] The measuring head 10, which in this embodiment is designed,
i.e., configured, as an endoscope, is inserted into the bore 6 to
be examined, the optical system 14 detecting an image of the inner
wall 4 of the bore 6 along a circumferential lateral surface line
and imaging same on the image sensor 16. By evaluating the recorded
brightness image, i.e., the output signals of the image sensor 16,
it may be concluded, using known methods of image processing and
pattern recognition, whether an anomaly or defect is present on the
inner wall 14.
[0028] The measuring beam 24 and the reference beam 30 of the white
light interferometer 20 result in simultaneous interference on each
pixel of the image sensor 16; by positioning the reference mirror
32, for each pixel of the image sensor 16 it may be determined when
the modulation is at a maximum. When the modulation of the
correlogram is at a maximum, the associated positioning path of the
positioning unit 36 corresponds to the maximum value of the point
on the inner surface 4 which is imaged on this pixel. Surface depth
information may be obtained in this way, so that the topography of
the inner surface 4 may thus be determined. Based on the surface
depth information, it may be concluded whether a detected anomaly
is a depression in the surface which forms a surface defect, or is
an elevation on the surface caused by soiling, for example.
[0029] The testing device according to the invention is thus
improved with regard to the detection of surface defects in a
cavity in a workpiece.
[0030] Depending on the particular requirements, the surface depth
information may be determined for each pixel of the recorded
brightness image, so that the topography of the inner surface of
the bore may thus be determined over the entire surface. However,
it is also possible to determine the surface depth information, and
thus the topography of the inner surface, not over the entire
surface, but instead at individual surface locations as needed. In
this regard it is possible and meaningful in particular to
determine the surface depth information only at the surface
locations at which an anomaly has been identified, since only those
surface locations at which an anomaly exists are important for the
test result. Thus, in principle there is no need for determining
the surface depth information at surface locations without
anomalies.
[0031] By means of the bore testing device according to the
invention, when an anomaly is detected it may thus be concluded
whether this is, for example, a depression resulting from a surface
defect, or an elevation caused by soiling which may possibly be
eliminated by removing the soiling. Thus, due to the surface depth
information which is available using the bore testing device
according to the invention, the test result is much more meaningful
than in conventional devices.
[0032] While this invention has been described as having a
preferred design, it is understood that it is capable of further
modifications, and uses and/or adaptations of the invention and
following in general the principle of the invention and including
such departures from the present disclosure as come within the
known or customary practice in the art to which the invention
pertains, and as may be applied to the central features
hereinbefore set forth, and fall within the scope of the
invention.
* * * * *