Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
  • G01B11/026—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring distance between sensor and object
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C3/00—Measuring distances in line of sight; Optical rangefinders

Definitions

• the present invention relates to a device for determining positions or movements, said device comprising a carrying body (10) carrying a read pattern comprising at least two types of regions, and at least one read-out means (12) arranged to read the read pattern, the carrying body and the read-out means being movable relative to one another.
• Fig 1 is a schematic block diagram of a meter of degrees in accordance with a preferred embodiment of the invention.
• Fig 2 is a more detailed view of the degree meter of Fig 1 ;
• Fig 3 is a cross-sectional view of the degree meter of Fig 2 ;
• Fig 4 is a schematic view of a meter of distances in accordance with one embodiment of the invention.
• Fig 6 is a schematic representation of a position and determination device intended for a rotational body in accordance with a further embodiment of the invention. Detailed Description of Preferred Embodiments
• the invention concerns a device for measuring angles, and a first embodiment of the angle meter in accordance with the invention is shown in Fig 1.
• the angle meter comprises a reader part 1 which, senses the current angle and which in response thereto issues an angle-indicating signal, and processing part 2, which transforms the output signal from the reader part into an angle signal, and a user part 3, which uses the signal representative of that angle issued from the processing part.
• the device could comprise one or several memory means 4 to ensure safer function.
• the reader part in accordance with the invention comprises a disc 10, which is mounted for rotation about a shaft 11 extending at right angles to the plane of the disc, and at least one read-out means 12, which is located above the plane of the disc to read the disc.
• the disc is formed with a reflecting surface and with a read pattern comprising at least two types of fields/regions producing distinguishable reflected signals.
• the read pattern is formed by fields located at different levels, i.e. in the form of pits made in the surface, like in the case of conventional compact discs.
• the fields also have the appearance of areas enclosed by two radii departing from the axis of rotation of the disc and by two arcs of a circle between the radii.
• Other configurations of the fields are, however possible within the scope of the invention.
• compact discs should be understood in the present description all available types of laser discs.
• the fields of the read pattern preferably are arranged in circles extending around the axis of rotation of the discs.
• the fields could be in the shape of helical tracks running outwards, towards the periphery of the disc, and the read-out means is arranged to follow the pitch of the helical track when the disc rotates.
• a commercially available standard compact disc could be used.
• One problem when standard discs are used that have helically configured tracks in the form of apertures laid out in turns extending from the centre of the disc towards the peripheral border thereof is, however that normally, the number of apertures varies from one turn to the next, depending on the distance of the individual turn from the centre of the disc.
• a third way is to burn into the disc a "looping" track. This means that when the player reaches the end of the track, the disc contains information, which may be interpreted by the reader head based on the read-out activity and which indicates that the reader head now is to return to a track that it has passed through previously.
• the read pattern could also be configured to comprise identifiable information.
• a pattern could be located internally of the metering track, i.e. such that the read pattern will have a width comprising at least two and preferably several reading fields positioned one radially internally of the other.
• the pattern extending radially from the centre of the disc could in this case contain digital information, indicating the degrees, and in this manner the degrees may be read directly, without resetting of the disc and calculation.
• the code preferably is read radially from the centre of the disc, but obviously it is likewise possible to read in the opposite direction.
• the different levels of reflection may be made use of by analysis of the amount of light of a specific wavelength, the different levels being distinguishable from one another. It is however also possible to use two or several different wavelengths of the emitted light, as will be described in more detail in the following.
• the size and configuration of the fields could also be made use of to identify one or several positions along the track.
• An aperture located at the zero point could, for instance have a considerably larger size, making it easy to identify.
• the read pattern as defined above could be arranged in a circular or helical configuration, i.e. closed or open. As discussed above, the track could be formed on a disc. However, it is likewise possible to form the read pattern in a circular or helical pattern on a cylindrical jacket face, such as externally on a shaft or the like.
• An open read pattern could also be arranged essentially linearly or be configured differently, provided that the read-out means is able to follow the track. In this case the read pattern could be used to detect displacements in one plane.
• the read pattern could be in the shape of a tape or the like that could be interconnected with the carrying object.
• the track could be worked directly into the carrying object, such as directly into the disc surface of the disc or directly into the jacket face of a cylindrical body.
• the read pattern could be produced for instance by punching, moulding or burning by means of a laser.
• the pattern in accordance with the invention could be used also for other purposes, such as to store information.
• This solution could be used e.g. to improve the storage capacity of conventional compact discs.
• the pattern in accordance with the invention makes it possible to provide a protective translucent layer of for instance plastics on top of the pattern. This arrangement increases e.g. the dirt- repellent properties.
• a disc could be used to carry the read pattern.
• the disc could be a commercially available compact disc.
• compact disc should be understood in the present document all types of available laser discs.
• the disc Since normally the disc need not be exchanged, it may be mounted in a stationary position. This makes the entire device more stable and less impact-sensitive. In addition, it becomes less expensive and more simple to manuf cture .
• the disc need to withstand high temperatures, it may be manufactured from glass or some other heat-resistant material.
• the reflective layer on the disc could also be replaced by other heat-resistant reflective materials .
• the read-out unit 12 comprises a source of light and a measuring means, preferably integrated in the same reader head.
• the measuring means is a sensor arranged to register the way the light from the source of light is reflected by the various fields on the disc.
• the source of light is a laser and the measuring means preferably is an interferometer. This is particularly suitable in cases when the fields of the disc are reflective fields located at different levels, whereby different degrees of extinction are obtained of the light entering the interferometer, depending on the route travelled by the light.
• the reader head issues one pulse each time it meets an aperture, the output signal consequently forming a pulse train.
• the pulses By counting the pulses it is possible to gain knowledge on the number of apertures that has passed by. These pulses form the digital data that the processing unit is then to convert into angle data.
• the processing means 2 comprises a processing unit, which is connected to the read-out means 1 and which may be a processor, a micro-chip or the like that interprets the signals from the read-out means to produce the torsion angular position of the disc.
• the processing unit is arranged to continuously supply data on the torsion angular position of the disc.
• the device may be made more impact-resistant. For example, a signal read some hundredths of a second previously, may be stored in a memory buffer. In case of power failure, the gap may be filled with the aid of the memory buffer. This is true, however, only of angle meters wherein the disc rotates at an essentially constant speed.
• the memory may retain the 10 latest values.
• wavelengths it is possible to use several separate reader units, for example one for each wavelength.
• light comprising several wavelengths or a range of wavelengths for illumination of the read pattern may be used.
• detection means a division of the light according to wavelength may be made, for example by means of a prism, and only the desired wavelengths are used for the detection function. In practical terms, this may be effected for example by means of a multi-interferometer or a CCD could be arranged after the separation of wavelengths.
• Another possibility is to separate directly in an interferometer or the like the degree of reflection concerning the various wavelengths without first separating the reflected light with respect to wavelength.
• the reading function is effected from two or several superposed read patterns.
• the read pattern is exposed to severe environmental conditions, such as extreme heat, pollution, vibrations and the like. This may be the case when the angle meter is intended for measuring rotating shafts or the like, as will be described in closer detail further on. In the case of such applications, adaptation of the reader unit is required to make it less sensitive.
• the lens arranged to focus the reflected beams towards the detection means normally is movably mounted in order to allow focusing corrections during operation of the device.
• the lens and the detection means could instead be fixedly interconnected, which eliminates the problems of vibration- induced error focusing.
• the sensitivity to pollution is reduced, and in addition, this structure can be made more robust and less heat -sensitive .
• correction may be effected by choosing the best-focused detection means. This could be done by guiding the reflected light towards the chosen detection means with the aid of a movable mirror or the like, although preferably all detection means are instead illuminated simultaneously. This may be done by division of the light beam by means of a prism, semi-transparent mirrors or the like, and thereafter the signal issued from the best- focused detection means is chosen. Alternatively, or as a supplement, it is likewise possible to make the detection means more robust by enlarging the area of the detection surface that receives the reflected radiation, which reduces the sensitivity to error focusing.
• the detection means it is possible to locate the detection means further away from the read pattern by providing means for transfer of light from the preferred position for respectively emission of light towards the read pattern and reception of reflected light.
• Such transfer means could be e.g. an optical fibre or the like. In this way, the sensitive equipment may be moved to less exposed locations, thus reducing the problems of pollution, vibrations and heat.
• the read-out means preferably is attached to a stationary part of the device, such as a chassis or a housing 5.
• the disc preferably is interconnected with a movable part of the device, such as a laser diode 6 or the like, and the housing 5 and the laser diode 6 may be displaced relative to one another with the aid of a screw means, such as a micro screw 8.
• the degree-value data computed by the processing unit 2 are forwarded to a user part 3, such as a data package.
• the user part could be for instance a display or the like, indicating the degree data.
• the degree-value data could also be transferred to some other unit, which makes use of this signal directly for control purposes or the like.
• the angle meter in accordance with the invention could also comprise stabilising means 9 or the like to ensure stable and firm movements of the disc 10.
• the angle meter in accordance with the invention may be used in a variety of fields, where the number of revolutions need to be counted or angles be measured.
• suitable areas of application may be mentioned in optical distance measurement means, in robot-control means for precision welding purposes, in inductive sensors and other measurement equipment, in observatories, in tachometers, in targeting systems and radar systems.
• Two basic fields of applications are, however significant, viz.:
• the device in accordance with the invention could also be designed as an absolute-value sensor, and thus be able to produce exact values without having to be reset. This is achieved by means of a reserve source of energy and a memory, as described previously. However, it could also be achieved by providing identifiable information in predetermined positions on the face of the disc, as described above.
• An angle meter in accordance with the invention is advantageously used for distance- measurement purposes, for example.
• the principle behind a distance meter of this kind is based on trigonometric relationships, from which, with knowledge of two values, i.e. the angle (v) and a known length of one of the catheters (x) , it becomes possible to derive the length (y) of the other catheter and/or the length of the hypotenuse. With increasing length, the accuracy of the angle becomes increasingly important, and consequently very precise angle meters are required for this purpose.
• the distance meter preferably comprises two laser diodes 6, 7 spaced a known distance (x) apart. The distance could be for instance one meter.
• One of the laser diodes 7 is fixedly mounted whereas the other laser diode, as mentioned earlier, is rotary and interconnected with the disc of the angle meter. Rotation of the laser 6 thus results in rotation of the disc mounted underneath. The latter is in turn read by the reader head.
• the angle signal is then transformed for instance by means of a stored table of tangential values and is multiplied by the distance x separating the lasers, which gives the value of the distance from the fixed laser 7 and to the point where the beams cross.
• the distance meter as defined above may of course be used in distance measurement applications of all kinds.
• the precision of the angle meter opens up the fields of possible uses for the meter, such as for calculation of areas, obtaining building construction measurements, map interpretation, navigation, and so on.
• the use of the distance meter as defined above could be effected in the following manner.
• the distance meter, set in a zero position, i.e. with the beams being parallel, is directed so as to point at the target, whereby two laser points will appear side by side.
• the display 3 of the meter on which display the distance to the target may be shown is then read.
• the display shows the distance to the beams-meeting point also during the very process of adjustment, when one beam is being rotated.
• a further advantage of the distance meter is that it does not have be located at the place to which the distance is to be measured, nor does a reflecting prism or other similar means have to be set up at that place .
• At least one read pattern 13 is arranged for example on the jacket face of the rotating object.
• the field areas of the track could in this case extend either in an axial direction, 13a, to measure rotational movements R of the rotating object, or in a tangential direction, 13b, to measure movements A in an axial direction.
• fields are arranged in both of these directions. This may be effected by arranging a sequence of several distinguishable tangential read pattern axially, one after the other.
• the meter can thus be used to indicate the angle of rotation as well as axial displacement, a feature which is of interest for estimation of for instance load on bearings and the like.
• the tracks could be made distinguishable by arranging identifiable points of reference in the tracks, as discussed above.
• the read pattern could, as already mentioned, be designed to indicate axial displacements only.
• One such pattern 13b may consist of depressed areas in the form of rings arranged in sequence in an axial direction around the rotary body.
• Separate read patterns 13a, 13b with fields that have a larger extension in the direction opposite to the read-off direction could also be used when it is desirable to take measurements in several directions. In this way, the sensibility to vibrations is reduced and so is the problem of error readings. It is, however, possible to use one single pattern only, which is designed to allow positions and movements to be determined in several directions.
• the meter in accordance with the invention makes it possible to obtain high precision and accuracy while at the same time the meter is comparatively simple and inexpensive to manufacture .
• a disc or a similar radially projecting part 14 on the shaft or the cylindrical body having a face that is not parallel to the axial direction and that preferably comprises a plane extending at right angles to the axial direction, in order to carry the read pattern 13c, like in the meter described previously.
• the track in this case comprises concentric rings. In this manner displacements F in the radial direction may be detected, which is useful in order to detect bearing play.
• One of several of the patterns described above thus may be used simultaneously, and one or several read- off means 12 may be provided to read these patterns.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optical Transform (AREA)
• Electromagnetism (AREA)
• Engineering & Computer Science (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Length Measuring Devices By Optical Means (AREA)

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• 1999
  • 1999-12-20 SE SE9904661A patent/SE9904661D0/sv unknown
• 2000
  • 2000-12-20 WO PCT/SE2000/002618 patent/WO2001046644A1/en active Application Filing
  • 2000-12-20 AU AU25667/01A patent/AU2566701A/en not_active Abandoned
  • 2000-12-20 EP EP00989122A patent/EP1247071A1/en not_active Withdrawn

Non-Patent Citations (1)

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