HK1170310B - Coordinate measuring device - Google Patents

Description

The invention relates to a coordinate measuring device and a method for operating a coordinate measuring device according to the general concept of the corresponding independent claims.

The Technical Standards

The measurement of the position of moving targets is carried out by means of coordinate measuring devices, often called laser trackers. The term laser trackers refers to devices that have at least one distance meter operating with a focused laser beam (referred to as a measuring beam in the following description). For example, a mirror rotating about two axes is used to adjust the direction of the measuring beam to the target and record the angle relative to the axes of rotation. The target to be measured is returned with a retroreflector (in particular a cube prism or an arrangement of three mirror beams directly adjacent to each other), whereby the reflector is carried by the measuring instrument at the point of impact of the laser beam.

The measurement data obtained define the parallel displacement of the measuring beam reflected and are used to control the measuring beam direction so that the measuring beam follows the target (tracking) when it moves. This means that the measuring beam direction or the orientation of the mirror is changed accordingly to reduce or maintain the parallel displacement between the measuring beam and the measuring beam.

WO 2007/079600 A1 describes various arrangements of optical rangefinders and image sensors. In one arrangement (Figure 4) a survey camera (104), a position-sensitive diode (109) operating in the visible spectrum and a zoom camera (106) are all coupled into the measuring light path of a rangefinder (200, 300). The position-sensitive diode (109) must operate in the visible range to be able to accurately measure the beam of a He-Ne laser of an interferometer with targets. To capture reflective images, a reflector lighting (110) is placed outside the reflector light, which works in the range of the camera's viewfinder. The survey camera must operate in the range of view in order to be able to provide good quality image, especially in the range of colours.

US 6.504.602 B1 describes a theodolite with a rangefinder.

EP 2 071 283 A2 describes the use of two separate cameras with a wide and a narrow angle of view, each with its own light source coupled to the camera optics. The cameras are arranged separately, one of which is collimated with the focal line to a rangefinder, and operate with visible light.

The following shall be considered as a single product:

The object of the invention is to create a coordinate measuring instrument and a method for operating a coordinate measuring instrument of the type described above, which allow cost-effective and yet precise measurements.

This task is solved by a coordinate measuring instrument and a method for operating a coordinate measuring instrument with the characteristics of the corresponding independent claims.

The coordinate measuring instrument shall therefore have a support which can be rotated in relation to a base by at least two axes, the support being automatically oriented to a measuring aid which can be moved in space by rotation around these two axes by means of a control device. ▪ at least one optical distance measuring device for measuring the distance (along a measuring distance) to a measuring instrument moving in space;▪ an infrared light source and an optics (respective optical elements) for emitting an infrared target beam, with the target beam visible as an infrared target when reflected on the measuring instrument;▪ a fine-grained target unit for determining a fine position other than that of the image of the infrared target on a first position sensor, where the fine-grained target unit and the distance measuring device share a common output optics;▪ a second light source which reflects at least one light sensor, where the reflection of this light is only on a second target unit;▪ a second focus unit for determining the gross position of the target unit, where the second focus unit is on a second position sensor;

The control device shall be set up to orient the holder to the measuring device by rotation about at least two axes of the holder, measuring the fine position and the gross position.

This control may alternatively take into account the fine position and the gross position, for example by switching from the gross position to the fine position when approaching the target, or it may be possible to have a control which processes both values simultaneously and selects and uses only one or both values for control.

The arrangement of the output and/or input optics of all units creates a compact unit capable of performing a wide range of functions, while still having a simple mechanical structure (only two driven axes).

Preferably, the optical axis of the fine-target detection unit is coaxial with the optical axis of the distance measurement device on a common measuring axis outside the coordinate measuring device. This assumes that the fine-target detection unit and the distance measuring device have a common exit optics. A common exit optics (or entry optics) of two beam paths means that the two beam paths exit the device into the device environment through the same optical element, such as a lens or a disc, or enter the device environment from the device environment.

In another embodiment of the invention, the optical axes of the fine-focus unit and the gross-focus unit outside the carrier are not coaxial, so that the optical axes either pass through the same exit optics but not coaxial, or they pass through separate exit optics.

Typically, the fine-focus unit shall have an aperture or viewing angle of less than 1° or less than 2° or less than 3°, preferably the gross-focus unit shall have an aperture of more than 3° or more than 10° or more than 15° and preferably up to approximately 30° (i.e. ±15°).

In a preferred embodiment of the invention, the fine-target detection unit and the gross-target detection unit are sensitive to light from the second light source in separate regions of the infrared spectrum (i.e. either the corresponding sensor or the combination of the sensor with a filter). The fine-target detection unit is sensitive to light from the infrared light source and the gross-target detection unit is sensitive to light from the second light source. Thus, the fine-target detection unit does not perceive light from the second light source and the gross-target detection unit does not perceive light from the infrared light source.

Preferably all optical and electrical elements of the different units are on the carrier, but it is also possible that individual elements of one or more units are on a base or in an intermediate unit and are connected to the carrier by fiber optic leads, such as laser sources or radiation separators and detectors.

Preferably, a further embodiment of the invention would be a camera with a view sensor that is sensitive at least in the visible range to roughly locate the measuring instrument by light in the visible range, preferably with a greater viewing angle than the rough target detection unit, which makes it possible to implement a three-step method of locating and tracking the measuring instrument by first searching for the measuring instrument through the view camera, then pointing the holder at the measuring instrument, and then approaching the measuring instrument with the rough target detection unit and then the fine target detection unit.

In the procedure for operating the instrument for coordinate measurement, the holder shall be oriented to the instrument by rotation about at least two axes of the holder, measured by fine position, rough position and optionally also by measurements from the survey camera.

In another embodiment of the invention, which may be implemented independently of or in combination with the components described above, the instrument has a support which is rotatable with respect to a base by at least two axes, and which can be automatically aligned with a space-moving measuring device by rotation about these two axes by means of a control device. ▪ at least one optical distance measuring device for measuring the distance (along a measuring distance) to a measuring instrument moving in space.▪ an infrared light source and an optics for emitting an infrared target beam, whereby the target beam is visible as an infrared target when reflected on the measuring instrument.▪ a fine-grained target detection unit for determining a fine-grained position as the position of the infrared target image on a first position sensor, whereby the fine-grained target detection unit and the distance measuring device have a common output optics. The optical axis of the fine-focus unit outside the coordinate measuring device is coaxial to the optical axis of the distance measuring device on a common measuring axis and the support is rotatable by an axial tilt at least approximately horizontal and by an axial tilt at least approximately vertical when the coordinate measuring device is in operation.

This makes it possible to manufacture the beam splitter for separating the beam path from the distance measuring device and the fine-target detection unit more easily: according to the state of the art, beam splitters are designed along the measuring axis in such a way that the beam path of the undirected light component in the measuring beam runs straight ahead, i.e. without any shift in relation to the measuring axis. (a) on the one hand, the measuring axis is to cut the swing axis and the tilting axis in order to keep the geometry of the measurement and thus the calculation of the position of the measuring aid as simple and precise as possible;

In accordance with this statement of the invention, the condition (a) is waived, which makes the calculations more complicated, but a translucent plate can be used instead of a prism as a radiation separator, which in turn allows for an improved separation of the radiation paths from the distance measuring device and the fine-target detection unit in terms of weight and cost.

In another embodiment of the invention, which may be realized independently of or in combination with the elements described above, the distance measuring device has a measuring light source for producing a measuring beam, a radiation divider which decouplines part of the measuring beam produced and a beam extender which expands the decoupling measuring light and thereby directs it to two separate detectors.

This makes it possible to direct the light from the measuring light source to two independent detectors without a (more expensive) radiation separator, one of which is used to control the intensity of the measuring light source and the other for safety reasons to trigger an emergency shutdown if the measuring light source output intensity is too high.

Other preferred embodiments are derived from dependent claims, whereby features of procedural claims can be combined with those of device claims as appropriate and vice versa.

The following is a brief description of the drawings:

The following is a detailed description of the subject matter of the invention by means of preferred examples of execution, which are shown in the accompanying drawings, each showing schematically: Figure 1 Essential components and the radiation path in a measuring instrument of the invention;Figure 2a sensor arrangement with a radiation divider;Figure 3an external structure of a measuring instrument; andFigure 4a shift between a measuring axis and a mechanical collimation axis.

The reference marks used in the drawings and their meanings are summarised in the reference list.

The method of application of the invention

Figure 1 shows the radiation path in a coordinate measuring device 1 in a preferred embodiment of the invention. The essential elements of the coordinate measuring device 1 are arranged in or on a medium 6, preferably in a common housing. A fine-target detection unit 2 generates an infrared target beam 24, and a distance measuring device 4 generates a measuring beam 44. The beams enter through a common output optic 63 from both and proceed preferably coaxially along a measuring axis 60. The medium also contains a gross target unit 3 with a second light source 33, and an overview camera 9. A control and control camera 7 captures and processes the various measuring values and controls the orientation of the sensor, and can also display information, in particular about the orientation of the camera 8 and the image sensors, on the device.

In a measuring mode or tracking mode, the coordinate measuring device 1 or the carrier 6 is oriented to a measuring device 5, such as a retroreflector such as a triple mirror or a cube prism. The two rays are reflected there and are visible as an infrared target or first target 25 for the coordinate measuring device 1 or as a second target 35 for the distance measuring device 4. The second target 35 is geometric and visible from the measuring device 1 at least approximately or even exactly at the same location in space as the first target 25. Conceptually and from the wavelength range, the two points 25, 35 are considered to be different, but distinct from each other.

The distance measuring device 4 is an absolute distance measuring device in the example shown, but can also be an interferometer, or a combination of both. In it, a measuring light source 43 emits the measuring light beam 44. This passes through a first beam splitter 451 to split the emitted light and a second splitter 455 to deflect the returning light. The two splitters 451, 455 are part of a sensor unit 45. A deflected portion of the emitted light is reflected by a beam extension 452 and directed to two intensity sensors 453, 454. One of these intensity sensors 453 is known to amplify the measuring light beam in a way that controls the intensity of the light, while the other 454 uses additional detection elements to ensure that the light is not reflected from the other. For example, a high-intensity sensor 452 is placed on a side of a beam or a series of two beams.

The light returning from the second beam splitter 455 is directed to a detector 456. The intensity detected there is used in a known way to determine the absolute distance, for example by the Fizeau principle. The outgoing and returning measuring light 44 passes through an electro-optical modulator 46, a quarter-wave plate 47, a beam extension 48, a diversion mirror 49 and a beam separator 41, which combines the measuring beam 44 with the infrared target beam 24 of the fine target unit 2 and separates them respectively on the return journey.

The fine-focus unit 2 has an infrared light source 23 which generates the infrared target beam 24 and which is coupled via a second coupling 28 and reaches the measuring axis 60 via an optional further beam extension 29 and the beam splitter 41 The infrared light emitted by the infrared light source 23 is thus coupled as a target beam 24 into the common beam channel of the distance measuring device 4 and the fine-focus unit 2. In the second coupling 28 the return light is coupled from the infrared target point 25 and reaches the first coupling 26 and the first band 20 to the first position sensor where a reflector image of the position sensor 22 is produced on the first position sensor 21 where the reflector image of the first position sensor 25 is produced.

In the first coupling 26 light from a pointer light source 27 is optionally coupled and is transmitted as a beam in a common beam path between the distance measuring device 4 and the fine-focus unit 2. This light from the pointer light source 27 is in the visible range, so that the measuring axis 60 is also visible to an operator when an object is encountered.

Err1:Expecting ',' delimiter: line 1 column 1078 (char 1077)

If the measuring instrument 5 reflects exactly the light received, for example with a triple mirror, the second light source 33 shall be located close to the input optics of the gross target unit 3.

To avoid mutual interference between fine target detection unit 2 and gross target detection unit 3, they are preferably operating in different wavelength ranges of the infrared spectrum. For example, the fine target detection unit 2 has a first bandpass filter 20 with a first throughput range, and the gross target detection unit 3 has a second bandpass filter 30 with a second throughput range, with the two throughput ranges not overlapping. For example, the two wavelength ranges are 890-920 nm for the fine target detection unit 2 and 835-865 nm for the gross target detection unit 3.

The second light source 33 may, in addition to the light in the IR range, also emit light in the visible range and thus also serve as illumination for the overview camera 9.

Figure 3 shows the schematic outline of a coordinate measuring instrument 1 with the elements already described: output optics 63, gross target unit 3 with two secondary light sources 33 on either side of the input optics of the gross target unit 30 and the overview camera 9 with its lighting 91, also with two individual light sources on either side of the input optics of the overview camera 9.

Figure 4 shows a schematic offset dZ between the infrared beam 24 inside and outside the beam 6 and its housing. Inside the housing, the infrared beam 24 cuts, for mechanical reasons, preferably both a vertical pivot axis 61 (or vertical axis) and a horizontal pivot axis 62 (or vertical axis) of the beam 6. The vertical axis 61 is perpendicular to pivot axis 62, which in turn is perpendicular to a target axis and to the measuring axis 60. The target axis (or mechanical collimation axis) corresponds to the course of the infrared beam 24 inside the beam (up to 41). The target axis 61 which represents the pivot axis 61 and the pivot axis 62 cut further apart in a single pivot axis. However, the invention of the pivot axis 62 does not only cut the pivot axis 61 but also the shape of the pivot axis 62 shown here.

The measuring axis 60 and the tilt axis 62 (or the pivot axis 61) are spaced at least half or a whole millimeter apart, preferably between 1.4 mm and 2.5 mm. The infrared target beam 24 of the fine target detection unit 2 is displaced by the beam splitter 41 which acts as a plate in the beam path of the infrared target beam 24 and acts as a mirror for the measuring beam 44.

1	Koordinatenmessgerät	44	Messlichtstrahl
2	Fein-Zielerfassungseinheit	45	Sensoreinheit
20	erstes Bandpassfilter	451	Strahlteiler
21	erster Positionserfassungssensor	452	Strahlaufweitung
		453, 454	Intensitätssensor
22	Fein-Position	455	Strahlteiler
23	Infrarot-Lichtquelle	456	Detektor
24	Infrarot-Zielstrahl	46	elektrooptischer Modulator
25	Infrarot-Zielpunkt	47	Viertelwellenplatte
26	erste Einkopplung	48	Strahlaufweitung
27	Pointer-Lichtquelle	49	Umlenkspiegel
28	zweite Einkopplung	5	Messhilfsmittel
29	Strahlaufweitung	6	Träger
3	Grob-Zielerfassungseinheit	60	Messachse
30	zweites Bandpassfilter	61	Schwenkachse
31	zweiter Positionserfassungssensor	62	Kippachse
		63	Austrittsoptik, Deckscheibe
32	Grob-Position	64	Zwischenträger
33	zweite Lichtquelle	65	Basis
35	zweiter Zielpunkt	7	Regelung, Steuerung
4	Distanzmessvorrichtung	8	Anzeigevorrichtung
41	Strahlteiler, halbdurchlässiger Spiegel	9	Übersichtskamera
		91	Beleuchtung für
43	Messlichtquelle	Übersichtskamera

Claims (14)

1. Coordinate measuring machine (1), having a carrier (6), which is rotatable with respect to a base about at least two axes (61, 62), wherein the carrier (6) is automatically alignable with a measuring aid (5) which is movable in space by way of rotation about said at least two axes (61, 62) using a control device (7), wherein at least in each case an entrance and/or exit optical unit of the following units are arranged movably together on the carrier (6), at least one optical distance measurement apparatus (4) for measuring the distance to a measuring aid (5) that is movable in space; a first light source (23) and optical elements (28, 29, 41, 63) for emitting a first target beam (24), wherein the target beam (24) is visible as a first target point (25) upon reflection at the measuring aid (5); a fine target acquisition unit (2) for determining a fine position (22) as the position of the image of the first target point (25) on a first position acquisition sensor (21), wherein the fine target acquisition unit (2) and the distance measurement apparatus (4) have a common exit optical unit (63); a second light source (33), which emits light at least in the infrared range, wherein said light is visible as a second target point (35) on a second position acquisition sensor (31) of a rough target acquisition unit (3) upon reflection at the measuring aid (5); the rough target acquisition unit (3) for determining a rough position (32) as the position of the image of the second target point (35) on the second position acquisition sensor (31); and wherein the control device (7) is adapted for aligning the carrier (6) with the measuring aid (5) by way of rotation about the at least two axes (61, 62) of the carrier according to the measurement of the fine position (22) and the rough position (32); characterized in that the rough target acquisition unit (3) is sensitive only to light in the infrared range and the optical axes of the fine target acquisition unit (2) and of the rough target acquisition unit (3) outside the carrier (6) are not coaxial.
2. Coordinate measuring machine (1) according to Claim 1, wherein the optical distance measurement apparatus (4) is an absolute distance measurement device or an interferometer, or a combination of both.
3. Coordinate measuring machine (1) according to Claim 1 or 2, wherein the light emitted by the first light source (23) is coupled into the common beam path of the distance measurement apparatus (4) and of the fine target acquisition unit (2) as the target beam (24).
4. Coordinate measuring machine (1) according to Claim 3, wherein an optical axis of the fine target acquisition unit (2) outside the coordinate measuring machine (1) is coaxial with respect to the optical axis of the distance measurement apparatus (4) on a common measurement axis (60).
5. Coordinate measuring machine (1) according to any one of the preceding claims, wherein the fine target acquisition unit (2) has an opening angle of less than 1° or less than 2° or less than 3°.
6. Coordinate measuring machine (1) according to any one of the preceding claims, wherein the rough target acquisition unit (3) has an opening angle of more than 3° or more than 10° or more than 15°.
7. Coordinate measuring machine (1) according to any one of the preceding claims, wherein the fine target acquisition unit (2) and the rough target acquisition unit (3) are sensitive in mutually separate ranges of the spectrum, and the fine target acquisition unit (2) is sensitive to the light from the first light source (23) and the rough target acquisition unit (3) is sensitive to the light from the second light source (33).
8. Coordinate measuring machine (1) according to Claim 7, wherein the fine target acquisition unit (2) has a first bandpass filter (20) having a first transmission region, the rough target acquisition unit (3) has a second bandpass filter (30) having a second transmission region, and the two transmission regions do not overlap and the first bandpass filter (20) filters out the measurement light of the distance measurement apparatus (4).
9. Coordinate measuring machine (1) according to any one of the preceding claims, having a pointer light source (27) for generating light in the visible range, and a coupling-in means (26) for coupling this light as a beam into the common beam path of the distance measurement apparatus (4) and of the fine target acquisition unit (2).
10. Coordinate measuring machine (1) according to any one of the preceding claims, having furthermore an overview camera (9), which is sensitive at least in the visible range, for rough localization of the measuring aid (5) on the basis of light in the visible range.
11. Method for operating a coordinate measuring machine, wherein the coordinate measuring machine has a carrier (6), which is rotatable with respect to a base about at least two axes (61, 62), wherein at least in each case an entrance and/or exit optical unit of the following units are arranged movably together on the carrier (6), at least one optical distance measurement apparatus (4) ; a first light source (23); a fine target acquisition unit (2), wherein the fine target acquisition unit (2) and the distance measurement apparatus (4) have a common exit optical unit (63); a second light source (33); a rough target acquisition unit (3); having the following steps:

    measuring the distance to a measuring aid (5) that is movable in space by means of the optical distance measurement apparatus (4);

    emitting a first target beam (24) by means of the first light source (23) and optical elements (28, 29, 41, 63), wherein the target beam (24) becomes visible as a first target point (25) upon reflection at the measuring aid (5);

    determining a fine position (22) as the position of the image of the first target point (25) on a first position acquisition sensor (21) of the fine target acquisition unit (2);

    emitting light at least in the infrared range by means of a second light source (33), wherein said light becomes visible as a second target point (35) on a second position acquisition sensor (31) of the rough target acquisition unit (3) upon reflection at the measuring aid (5);

    determining a rough position (32) as the position of the image of the second target point (35) on the second position acquisition sensor (31) of the rough target acquisition unit (3);

    automatically aligning the carrier (6) with the measuring aid (5) by way of rotation about the at least two axes (61, 62) of the carrier by means of the control device (7) according to the measurement of the fine position (22) and the rough position (32),

    characterized in that

    the rough target acquisition unit (3) is sensitive only to light in the infrared range and

    the optical axes of the fine target acquisition unit (2) and of the rough target acquisition unit (3) outside the carrier (6) are not coaxial.
12. Coordinate measuring machine (1) according to any one of Claims 1 to 10, wherein the carrier (6) is rotatable about a tilt axis (62) which extends at least approximately horizontally during operation of the coordinate measuring machine (1) and is rotatable about a pivot axis (61) which extends at least approximately vertically, and wherein the measurement axis (60) does not intersect the tilt axis, and/or the measurement axis (60) does not intersect the pivot axis (61), and wherein the measurement axis (60) and the tilt axis (62) are spaced apart from one another by a distance of at least a half millimetre or at least one millimetre, preferably between 1.4 mm and 2.5 mm.
13. Coordinate measuring machine (1) according to any one of Claims 1 to 10, wherein the distance measurement apparatus (1) has a measurement light source (43) for generating a measurement light beam (44), and a beam splitter (451) which couples out part of the generated measurement light beam (44), and a beam expander (452), which expands the coupled-out measurement light and thereby guides it onto two separate detectors (453, 454).
14. Coordinate measuring machine (1) according to Claim 13, wherein the beam expander (452) has a cylindrical prism or a series of adjacent, unipartite cylindrical prisms.