WO2005098509A1

WO2005098509A1 - Image-producing scanning device used to detect cavities

Info

Publication number: WO2005098509A1
Application number: PCT/EP2005/003548
Authority: WO
Inventors: Karl-Heinz Gaida
Original assignee: Endoscan Gmbh
Priority date: 2004-04-06
Filing date: 2005-04-05
Publication date: 2005-10-20
Also published as: DE202005005448U1

Abstract

The invention relates to an image-producing scanning device which is used to detect cavities, for the purpose of recognising surface changes and changes, in particular damage, below the surface, as well as simultaneously detecting the surface geometry. The aim of the invention is to produce said type of device which detects geometric data and also other parameters. Said aim is achieved by virtue of the fact that the inventive device comprising a light source which is used to emit an illumination beam, a rotating deflection device which enables a measuring respective illumination beam to be deflected onto the object which is to be examined, and a detecting, evaluating and storing unit, which enables a receiving beam reflected by the object to be detected and processed, is provided.

Description

Imaging scanner to detect voids

description

The invention relates to an image-forming scanning device for detecting cavities for the purpose of detecting

Surface changes and changes, especially damage, below the surface, as well as for the simultaneous detection of the surface geometry. The proposed solution is primarily used to identify the aforementioned properties and parameters in industrial buildings, such as in tunnels, sewer systems, pipeline systems of larger diameter, cooling towers, etc.

Due to increasing traffic volume, extended nature conservation and increasing technological possibilities, more and more and longer road and train tunnels are being excavated worldwide.

With the growing number and size, the time and manpower required for the necessary tests, the burdens for users, operators and test engineers increase.

In order to reduce the effort for the visual inspection and to objectify the results, the present invention is proposed, which for operators of highways, roads and rail networks, construction and planning offices, structural inspection engineers and operators of power plants and water supplies a measurement option at the highest level to support the main inspection and provides regular control.

On the basis of the prior art, the object of the invention is to specify a scanning method which allows a predeterminable number of defined measuring points to be determined, and at the same time, in addition to purely geometric data of the cavity to be measured, above all other parameters should also be detectable simultaneously. The invention is intended to enable the recording and storage of the entire inner surface of said cavities as a color or false image in different spectral ranges, as well as a profile determination.

Basically, scanning devices for measuring the spatial coordinates of an object with a light source for emitting a transmission beam, with a deflection device with which the transmission beam can be directed onto the object, and with a detector with which a reception beam reflected by the object can be detected, and corresponding evaluation units known.

Such a scanner is e.g. known from DE 33 15 576 A1. In this scanning device, the transmission beam generated by a laser is directed onto the object to be measured by a first pivotable deflection mirror. A second pivotable deflecting mirror directs a part of the transmitted beam reflected by the object to be measured onto a detector which is connected to an evaluation unit.

Such scanning devices are used to measure distances and to measure three-dimensional spatial profiles, such as road and rail tunnels. It is a common requirement that the measurement be carried out with sufficient speed and accuracy. In order to be able to detect irregularities, the measurement must be carried out with a measuring point grid, which extends over several meters from the center of the lane.

The respective distance should also be determinable as precisely as possible.

Since known devices, due to the spatial limitation of the beam path due to the mechanical suspension of the deflection mirrors, only permit scanning in a restricted solid angle range, a multiple pass through the cavity to be measured is required, the scanning mirrors used being subjected to movement from the outset, due mechanical instabilities, a decrease in accuracy is accepted.

On the basis of this prior art, an invention which is close to the present invention and which is intended to enable faster measurement of spatial profiles with higher resolution has been proposed. For example, DE 44 45 464 A1 proposes a scanning device in which spatial coordinates of an object are measured by means of a light source for emitting a transmission beam with a relatively large beam diameter, a deflection device with which the transmission beam can be directed onto the object, and with a detector with which a reception beam thrown back by the object can be detected, as well as with an evaluation unit, the scanning device being attached to a means of locomotion with which a movement in a translation direction can be carried out, with a mirror rotor arranged outside a housing of the scanning device, which via a tubular mirror rotor attachment in a fitting opening is rotatably mounted in a wall of the housing of the scanning device and can be set in rotation via a drive device about an axis of rotation, has a mirror element with which it enters the mirror along the axis of rotation through the mirror rotor attachment End transmit beam is deflectable at an angle to the axis of rotation to a rotation about the translation direction and with which the receive beam can be deflected in the region of the mirror on the axis of rotation. However, such a device is primarily suitable for measuring spatial coordinates. Due to the geometry of the laser beam there and the collection optics provided there, the detection of minimal cracks in the building, as aimed at by the present invention, is only possible to a limited extent. At the same time, the traversing and thus measuring speed of the device there is technically limited from the outset due to the type of laser beam deflection.

The present invention is therefore based on the object of specifying a scanning device which defines a predeterminable number It is possible to define measuring points, while at the same time with purely geometrical data of the cavity to be measured, with a crack line _. Up to 0.2 mm or better, especially other changes in the state of the object to be measured, such as cavities, gravel pockets, water damage, etc. should be detectable, ie a simultaneous acquisition of image, thermal and geometry data should be made possible. This has the advantage that the building only has to be driven on once and that all data can be clearly assigned. Furthermore, the device is intended to ensure a significant increase in the measurement speed compared to conventional methods.

The object is achieved by the characterizing features of patent claim 1. Advantageous refinements are the subject of the subordinate claims.

The essence of the present invention consists in a novel deflection principle for the intended use, which does not require any additional beam splitters, etc. A new type of polygon mirror is used to deflect the laser radiation and also radiation of other wavelengths, which has at least three, preferably four mirror pairs, two associated mirror pairs of one facet each enclosing an angle of 90 ° and via which coupling and decoupling occurs during rotation Measuring and receiving beams without disturbing further optical modules is made possible. These mirror pairs are arranged in a radially symmetrical manner on a carrier body distributed around its axis of rotation with an opening remote from the axis of rotation. In this case, at least one separate one is also distributed symmetrically about the axis of rotation of the polygon mirror and perpendicular to it, in at least three sectors, at equal angles

Imaging system, which can simultaneously represent the illumination source, which is essentially formed by long-distance high-performance microscope optics, which allows a predetermined point of the object to be measured to be imaged on a receiver surface. To the required multivalent In order to do justice to the use of the proposed scanning device, analogously to the imaging systems, however, a passive thermography system as well as an active laser distance measuring system for each sector are provided, for example, in each case equally centrally distributed symmetrically with an angular offset. The type of detector systems used is not essential to the invention and is determined exclusively by the required parameters to be detected; the only essential thing is that such detectors are used in an inventive arrangement that can be operated via the polygon mirror essential to the invention. It is therefore also within the scope of the invention to optimize the mirror surfaces of the polygon mirror to spectral regions which can be predetermined as desired. In addition, one facet sensor is provided per sector, not per mirror pair, with the help of which a starting point for the mirror pair currently arriving in the respective sector upon rotation can be detected and which triggers a predeterminable speed-independent counting pulse sequence for the downstream evaluation electronics.

The invention will be explained in more detail below using an exemplary embodiment. 1 shows an embodiment of a special polygon mirror with exemplary assigned transceiver units in a schematic perspective view, FIG. 2 shows a more detailed side view of the polygon mirror according to FIG. 1 with assignment of an essential receiver component, FIG. 3 shows a schematic view of the overall structure of the proposed 4 a front view of an exemplary arrangement of the polygon mirror and the sectors assigned to it Transmitter, receiver, detector and evaluation modules and FIG. 5 an example of the detection of a tunnel cross section.

FIG. 1 shows, by way of example, an embodiment of a special polygon mirror 1 with associated transceiver units in a schematic perspective view and the solid angle that can be detected by the individual mirror pairs with respective overlapping areas. In this specific exemplary embodiment, 1 denotes that which is essential to the invention

Polygon mirror, which rotates around the indicated axis, realizes a signal exchange with four imaging systems E1, E2, E3, E4 provided in this example, each via mirror Sp. The connection lines shown in each case between the individual receivers E, via the mirrors Sp to the polygon mirror partial surfaces located at the rear in the image plane, represent the path that the respective received light beams take, for example, from the object wall to the respective receiver. Which path the light beam takes, for example, becomes clearer from FIG. 2. FIG. 1 also shows how the transmitted / received light beam sweeps across the room, in the example in four sectors that partially overlap (see the radial border and the sector sections).

FIG. 2 shows a more detailed side view of the polygon mirror 1 according to FIG. 1 with assignment of an essential transceiver component. The polygon mirror 1 is mounted on an axis XX of a motor 2. In the example, the polygon mirror 1 has four mirror pairs 11-11 ', 12-12 ", 13-13' and in Fig. 1 covered by the pairings 11-11 ', the rear pair 14-14', which is circumferential around its In the context of the invention, it is essential to provide at least three such mirror pairs. The two individual mirrors assigned to each mirror pair are arranged at an angle of 90 °. These mirrors each have a highly precise surface treatment, as they do is customary and technologically feasible according to the state of the art For example, according to FIG. 2, a laser light source 4, which emits light of one or more visible spectral ranges, for example through a partially transparent mirror Sp, the type of illumination being insignificant in the context of the present invention, radiated perpendicularly onto the first mirror 12 ', from there reflected on the assigned opposite mirror 12 and from there deflected perpendicularly to an object wall (not shown) (for example a tunnel inner wall). The object wall could also be illuminated in any other way, but is particularly expedient in the manner described, since it is made possible with one and the same device and the respective measuring surface is illuminated identically. In the context of the invention, however, it is essential that at least one separate imaging system per sector (only one such imaging system, here E2, is shown in FIG. 2 for reasons of clarity), which in the example is formed by long-distance high-performance microscope optics, is provided. This optics is selected in a professional manner so that it is adapted to the object conditions and the mirror sizes used. In contrast to the proposals according to the known state of the art, the size of the object field per measurement or pixel is not determined by the illuminating light source used, but only by the geometry of the receiver used and the imaging scale of the imaging optics used.

FIG. 3 only schematically illustrates further necessary, but not essential to the invention, to get an idea of the mode of operation of the overall device. For example, the illustrated imaging unit E2 is followed by an analog signal processing, a photometer, and, for example, a laser radar, a thermography system, etc., for which only one module 5 is designated by way of example. Subsequently, pure data processing and storage modules etc. are provided, which include, for example, PCI frame grabbers, the driver software and scanner control. These are in Fig. 3 comprises a dashed and designated 3 frame.

The further modules to be provided within the scope of the invention and their arrangement with respect to one another are shown more clearly in FIG. 4 in a front view of the polygon mirror 1. There it is indicated that centrally symmetrical about the axis of rotation XX of the polygon mirror 1 and perpendicular to it (in deviation from FIG. 1) in at least three sectors S1, S2, S3 in each case equally angularly distributed, i.e. here offset by 120 °, a separate imaging system E1 , E2, E3 is provided, through which the lighting could be realized at the same time. A passive thermography system T1, T2, T3, which is formed in the example by an MCT sensor with GaAs optics, is also provided for each of these imaging systems, each offset by 40 ° in the example, in a centrally symmetrically uniform manner. This thermography system is selected so that it ensures the detection of at least 10,000 pixels per revolution in a spectral range from 2 to 12 μm.

Within the scope of the invention, analogous to the above systems, a common active laser distance measuring system L1, L2, L3 per sector S1, S2, S3 is provided in a further uniformly distributed angular offset, here of 40 °. It can also be seen from FIG. 4 that so-called facet sensors F1, F2, F3 are provided. In the example, these are formed by light barriers that depend on the angle of reflection

Light reflection, emitted, for example, from an auxiliary laser (not shown), which is provided independently of the respective lighting sources, is received as soon as a pair of mirrors 11-11 'to 14-14' arrives upon rotation of the polygon mirror 1 into a predetermined starting position. This received pulse triggers for everyone in this scanning sector, in

Example S1, S2, S3, arranged sensor system the scanning, analog-digital conversion, storage and data transmission of an electronically freely selectable number of measuring points (for example 10,240 per scanning sector). Since it is not the angle of rotation of the polygon mirror, but the angle of reflection of the mirror pair that is recorded By means of a suitable arrangement of the facet sensors, production-related geometric deviations of the mirror pairs of the polygon mirror can be corrected. In addition, an index sensor I is provided, which defines a mirror pairing during the measurement as the first, for the purpose of establishing a zero point, and thus supplies the subsequent evaluation units 3 with a signal for unambiguous assignment of the signals originating from the individual mirror pairings for the purpose of synchronization.

It can be seen from the above description of the specific exemplary embodiment that any other

Detector systems can be arranged with the same requirements as described above, so the invention is not restricted to this exemplary embodiment.

Figure 5 shows schematically the detection of a

Road tunnel cross section based on an arrangement of light receivers E and thermal sensors T according to FIG. 3. For example, the left sector of 124 ° (which corresponds to the aperture of a pair of mirrors used in the example) denotes a first field swept by a pair of mirrors in an optical channel, for example second sector, also overlapping on the right, of likewise 124 °, the field swept by the subsequent second pair of mirrors, in the example also in an optical channel. In the example offset by 40 °, a further sector can be seen, which, for example, is intended to characterize the field which is simultaneously covered by a thermographic sensor.

Determined by its position with regard to the assigned facet sensor, its start pulse and the selected number of pulses, each sensor is thus assigned a unique scan area. This is shown hatched in FIG. 5 for two optical channels, for the sectors of two imaging systems offset by 120 degrees. The intersection of the sectors, cf. Fig. 5, for example in the top of the tunnel, is desired and can be used for a clearer representation of the scan sectors for the subsequent evaluation be used to advantage. The sectors shown are run for each mirror pair.

The image-forming scanning device claimed here for the detection of cavity profiles, which is mounted on a corresponding transport vehicle, enables complete detection of all object-relevant data at a solid angle at driving speeds in the order of magnitude, for example, of 4 km / h with a single pass, for example through a tunnel of 360 °. The above-described, staggered arrangement of the individual measurement and the systems triggering the measurement guarantees a speed-independent, unambiguous and jitter-free assignment of the individual image, thermal and distance data to a spatial coordinate system of the object to be measured, regardless of the polygon mirror. With the proposed scanning device based on a

Means of transport installed, for example transported through a tunnel, achievable travel speed is only determined by the desired resolution of the parameters to be detected in the direction of transport and can thus be optionally specified. With comparable resolutions to known devices according to the state of the art, however, the scanning device proposed here can achieve four times higher driving speeds, which represents a considerable advantage with increasing inspection requirements.

All the features shown in the description, the claims below and the drawings can be essential to the invention both individually and in any combination with one another. LIST OF REFERENCE NUMBERS

1 polygon mirror

11-11 ', 12-12', 13-13 ', 14-14' mirror pairs

2 engine

3 evaluation unit

4 laser light source

5 Receiver unit E1. E2. E3, imaging system

F1. F2. F3 facet sensor

I index sensor

L1, L2, L3 laser distance measuring system

S1. S2. S3 sector Sp deflecting mirror

T1. T2, T3 thermography system

X-X (motor) axis of rotation

Claims

1. Image-generating scanning device for detecting cavities, comprising a light source for emitting an illuminating beam, a rotating deflection device with which a measuring or illuminating beam can be directed onto the object to be examined, and a detector, evaluation and storage unit with which a the received beam thrown back by the object can be detected and processed, the entire scanning device being movable in a translational movement in the longitudinal direction of the object to be detected, characterized in that - a polygon mirror (1) which can be set in rotation is provided, which is circumferential about its axis of rotation (XX) evenly distributed, has at least three pairs of mirrors (11-11 ', 12-12', 13-13 "), the two individual mirrors (11,11 ';12,12';13,13") which are assigned to one another Include an angle of 90 ° with the opening away from the axis of rotation, whereby - centrally symmetrical about the axis of rotation (XX) u nd perpendicular to this in at least three sectors (S1, S2, S3), each equally distributed angularly, at least one separate imaging system (E1, E2, E3), via which the illumination can be realized simultaneously, which is a predetermined point of the object to be measured to be reproduced with pinpoint accuracy on a receiver unit (5), is provided, - analogously to the imaging systems (E1, E2, E3), but to the above imaging systems, each with an angular offset, centrally symmetrically evenly distributed per sector (S1, S2, S3) for further detector systems the same or different spectral ranges are provided and - in addition, one facet sensor (F1, F2, F3) is provided for each sector (S1, S2, S3). T. Image-generating scanning device according to claim 1, characterized in that the further detector systems are formed by passive thermography systems (T1, T2, T3).

3. Image-generating scanning device according to claim 1, characterized in that the further detector systems are formed by active laser distance measuring systems (L1, L2, L3).

4. The image-generating scanning device according to claim 1, characterized in that the polygon mirror (1) has four mirror pairs (11-11 ', 12-12', 13-13 ", 14-14 ') distributed uniformly around its axis of rotation (XX) and is centrally symmetrical around the axis of rotation (XX) and perpendicular to it in three sectors (S1, S2, S3) each equally distributed angularly and with an angular offset to each other a separate imaging system (E), a passive thermographic system (T) and a facet sensor (F) is.

5. Image-generating scanning device according to claim 1 or 4, characterized in that the optical axes of the separate imaging and lighting systems (E1, E2, E3) are arranged parallel to the axis of rotation (XX) of the polygon mirror (1) and the coupling of light onto the first individual mirror (11 ", 12", 13 ', 14') via a deflecting mirror (Sp).

6. Image-generating scanning device according to claim 1 or 4, characterized in that the facet sensors (F) assigned to each sector (S1, S2, S3) each have a starting point for the currently arriving mirror pairing (11 -11 ', 12-12', 13- 13 ') and trigger a predeterminable speed-independent counting pulse sequence for the downstream evaluation electronics (3). Image-generating scanning device according to one of the preceding claims, characterized in that an index sensor (I) is additionally provided, which determines a pair of mirrors during the measurement as the first, for the purpose of establishing a zero point, and thus a signal for the subsequent evaluation units (3) for unambiguous assignment of the delivers signals originating from the individual mirror pairs for the purpose of synchronization.