GB2156514A - Shape sensors - Google Patents

Shape sensors Download PDF

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Publication number
GB2156514A
GB2156514A GB08408084A GB8408084A GB2156514A GB 2156514 A GB2156514 A GB 2156514A GB 08408084 A GB08408084 A GB 08408084A GB 8408084 A GB8408084 A GB 8408084A GB 2156514 A GB2156514 A GB 2156514A
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GB
United Kingdom
Prior art keywords
means
shape
member
transmitting
emr
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08408084A
Other versions
GB2156514B (en
GB8408084D0 (en
Inventor
Minoo Homi Edalji Patel
Lawrence John Godfrey
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
London University College
Original Assignee
London University College
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by London University College filed Critical London University College
Priority to GB08408084A priority Critical patent/GB2156514B/en
Publication of GB8408084D0 publication Critical patent/GB8408084D0/en
Publication of GB2156514A publication Critical patent/GB2156514A/en
Application granted granted Critical
Publication of GB2156514B publication Critical patent/GB2156514B/en
Application status is Expired legal-status Critical

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01BMEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00Measuring arrangements characterised by the use of optical means
    • G01B11/24Measuring arrangements characterised by the use of optical means for measuring contours or curvatures
    • G01B11/245Measuring arrangements characterised by the use of optical means for measuring contours or curvatures using a plurality of fixed, simultaneously operating transducers
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00Detecting, measuring or recording for diagnostic purposes; Identification of persons
    • A61B5/103Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/107Measuring physical dimensions, e.g. size of the entire body or parts thereof
    • A61B5/1077Measuring of profiles

Abstract

A contactless shape sensor comprises a ring (3) to encircle the body the shape of which is to be determined, the inner surface (7) of the ring having at least one array of electromagnetic radiation (EMR) emitters encircling the ring and a corresponding array of EMR sensors. The EMR emitters are capable of emitting a signal over a wide angle and the EMR sensors have a wide field of view. When an EMR emitter A is switched on, the EMR sensors at B and C detect the edges of the shadow cast by the body thus defining lines AB and AC tangential to the shape (1) within the ring. By switching the emitters (A) around the ring in turn further tangential lines to the shape can be defined, and the resulting information can then be used to re-create the image of the body encircled by the ring. The device is particularly useful for determining the shape of a person's leg at a location where an amputation has been made. <IMAGE>

Description

SPECIFICATION Shape sensors This invention relates to shape sensors and in particular to contactless shape sensors.

There are a number of applications in engineering where the surface profile of an arbitrary object needs to be determined. This requirement is associated with the general problem of extracting meaningful data by digital processing of signals from optical sensors based on television camera tubes. The solution of this prcblem requires such a large amount of processing power and sophisticated computing algorithms that a low cost geneial purpose contactless shape sensor of this type is not likely to be developed for some time.

The invention provides a shape sensor for detecting the surface shape of a member comprising, means to transmit wide-angle beams of electro-magnetic radiation (EMR) at the member, means to receive the EMR spaced from the transmitting means to allow the member to be interposed between the transmitting and receiving means whereby a "shadow" or area relatively free of EMR is created on the receiving means by the obstructions member, means to detect the limits of the "shadow" on the receiving means and means to cause said beams to be operated at a multiplicity of different positions around an axis between the transmitting and receiving means and means to compose from the limits of the "shadow" detected on the receiving means an image of the member disposed between the transmitting and receiving means.

Preferably a multiplicity of transmitting means is provided in an annular array to receive the member the shape of which is to be sensed and a multiplicity of receiving means is provided in an annular array located coaxially with the array of transmitting means.

More specifically, a plurality of arrays of transmitting means may be provided with the means in one array being out of register with the means in the other array or arrays and a corresponding plurality of arrays of receiving means are provided.

In the latter arrangement means may be provided for actuating the transmitting means in the or each array in sequence around the annulus.

In a specific construction according to the invention the arrays of transmitting and receiving means may be mounted on the inside of an annular member to receive the member the shape of which is to be sensed.

In any of the above arrangements the transmitting means may each provide a wide or narrow angle beam of electro-magnetic radiation, by direct transmission, reflection or EMR guide.

Specialised contactless shape sensors can thus be provided for a range of applications.

These could, for example, be used as attachments to robotic devices, for the measurements of cross-sections or in automated flexible manufacturing centres.

The following is a description of some specific embodiments of the invention reference being made to the accompanying drawings in which: Figure 1 is a general view of a shape sensor in operation, Figure 2 is a plan view of a sensor, Figure 3 is a side view of Electro-magnetic Radiation (EMR) emitters and sensors, and Figure 4 is an enlarged view of EMR emitters and sensors.

The device illustrated in the drawing comprises a hinged ring as shown in Figure 1, but a continuous ring may also be used. Other shapes, as necessary may also be used. These shapes do not have to form a closed loop. The ring 3, is hinged at 5 with a clasp at 6 to keep the ring closed up. The ring is placed around an arbitrary shape 2 with an arbitrary cross-section 1, which can vary along the length of the body. The ring, 3 has arrays of electro-magnetic radiation (EMR) sources and sensors on its innei surface 7, and is equipped with signal cable 4, which can switch the EMR sources and scan the sensor outputs under the control of a digital computer.

Figures 2, 3 and 4 show details of one version of the contactless shape sensor. Figure 2 shows a plan view of the device built as a ring 3, around the cross-section to be sensed, denoted by 1. The ring is hinged at 5 with clasp 6 at the diametrically opposite end such that the ring can be placed around a shape or removed with ease.

The inner surface 7, of the ring is covered by arrays of EMR emitters 8, and EMR sensors 9. Figure 3 shows a side view of the ring with two strips of EMR emitters and sensors around the inner circumference of the ring.

Figure 4 shows an enlarged view of the emitter and sensor arrays. A series of alternate layers of EMR emitters and sensors allow higher effective densities of these devices and permit the sensor to be used for measurements at high resolution. Figures 3 and 4 show two alternating layers of EMR emitters and sensors.

The EMR emitters can be wide angle EMR emitting devices whereas the EMR sensors can be any appropriate type of EMR detector of small physical size but wide field of view.

the wavelengths of maximum EMR emission and EMR detector sensitivity are matched to each other but are also selected so as to be least affected by the wavelength of ambient light or other ambient EMR if operation under these conditions is necessary.

The arrays of EMR emitters and detectors are connected through their power supplies and signal conditioning equipment respectively to a digital computer. The EMR emitters are connected to a multiplexed digital to analogue or digital to digital interface or logic interface through which the computer is capable of switching on any single EMR emitter or a selectable combination of emitters. At the same time, the EMR sensors are connected to an analogue to digital interface which can transmit digital signals to the computer detailing the EMR levels detected by the sensors.

The computer can switch the EMR emitters on or off and detect their resultant EMR sensor outputs under program control. A variety of graphics peripherals can be used to display the cross-sectional shape.

Figure 2 illustrates the basic principle of operation of the device. If an EMR emitter at A A is switched on, then, EMR sensors at E and C will be on the borderline between detection and non-detection of the EMR emitted at A.

Thus, the circumferential region BAC will be detected whereas the region BDC will be undetected. The positions of E and C are defined by the change in detected EMR level from detection to non-detection. This allows the positions of lines AB and AC which are tangential to the shape 1, to be determined.

By switching on a second EMR emitter A' and determining the positions of E' and C', further tangential lines to the shape (A',B' a A'C') can be defined.

Thus, a computer can be used to switch the EMR emitters on and offin various predefined ways under program control and to detect the EMR sensor outputs so that the precise crosssection of the shape in the ring can be defined from the series of tangents that become available. One possible switching configuration is to alternately switch one EMR emitter on, scan all the EMR sensors, then switch the EMR emitter off but switch the adjacent emitter on and repeat the process.

Another strategy is to switch the IMR emitters on and off using various types of 'random walk' patterns which are able to complete the detection of a shape more rapidly than the sequential switching described earlier.

A A further refinement would be to switch on all the EMR emitters simultaneously or in appropriate patterns with each emitter giving out a characteristic type of EMR. The characteristic might be imparted by choice of EMR spectrum, switching frequency, modulation, etc of the emitted radiation. The sensor output signals can then be used to differentiate between emitters by electronic means or within the digital computer by signal analysis.

Each complete scan defines a profile in a single plane in two dimensions. Movement of the shape sensor device in a direction perpendicular to the original plane coupled with further complete scans at regular increments of travel will permit a three dimensional profile to be built up.

The use of a computer allows fast completion of the scans required to fully define a shape. Proper programming of the computer would also allow use of this device by an untrained operator or under the control of a low level robot arm or industrial machine.

The performance of the shape sensor is a function of the width e, of each EMR emitter and the resolution of the sensors s, along the inner circumference of the ring. Thus, for a concentrically placed circular cross-sectional shape, the resolving accuracy of either face of the shape, as defined by its tangents will be given by the expression: s+e 2 Thus, for values of e = 0.25 mm and s = 1 mm, a radial dimension of the shape can be resolved to within 0.625mm. The effective value of s can be reduced by alternating arrays of EMR emitters and sensors regularly offset from each other by fractions of the dimensions s.

The nature of the shape sensor, described so far, is such that re-entrant cross-sections cannot be adequately defined-the device will define an area which is enclosed by all the possible tangents to the shape. However, by making the shape to be sensed possess a surface that is reflective to the EMR signals given out by the emitters, the re-entrancy limitation may be overcome. The surface of the shape to be detected may be made reflective by reflective covering, reflective paint, reflective self-adhesive tape, etc. The reflective element merely needs to be in intimate contact with the surface and of negligible thickness in comparison to the accuracy of measurement desired. A reflective covering, coating, etc of known thickness may also be used.

A laser source of EMR may be of particular use in the operation of the shape sensor even though this is a narrow angle beam of EMR.

The laser beam may be traversed through a wide angle by mechanical, optical or electronic means to replace the wide-angle EMR emitters.

Claims (2)

1. A shape sensor for detecting the external shape of a member comprising, means to transmit wide-angle beams of electro-magnetic radiation at the member, means to receive the divergent beams spaced from the transmitting means to allow the member to be interposed between the transmitting and receiving means whereby a shadow is created on the receiving means by the member, means to detect the limits of the shadow on the receiving means and means to cause said beams to be created at a multipiicity of different positions around an axis between the transmitting and receiving means and means to compose from the limits of the shadows detected on the receiving means an image of the member disposed between the transmitting and receiving means.
2. A shape sensor as claimed in claim 1 wherein a multiplicity of transmitting means is provided in an annular array located coaxially with the array of receiving means.
2. A shape sensor as claimed in claim 1 wherein a multiplicity of transmitting means is provided in an annular array to receive the member the shape of which is to be sensed and a multiplicity of receiving means is provided in an annular array located coaxially with the array of transmitting means.
3. A shape sensor as claimed in claim 2 wherein a plurality of arrays of transmitting means are provided with the means in one array being out of register with the means in the other array or arrays and a corresponding plurality of arrays of receiving means are provided.
4. A shape sensor as claimed in claim 2 or claim 3 wherein means are provided for actuating the transmitting means in the or each array in sequence around the annulus.
5. A shape sensor as claimed in any of claims 2 to 4 wherein the arrays of transmitting and receiving means are mounted on the inside of an annular member to receive the member the shape of which is to be sensed.
6. A shape sensor as claimed in claim 5 wherein the annular member is split along a diameter, the two parts being hinge together at one split in the annulus and means being provided for fastening the two members together at the diametrically opposite split.
7. A shape sensor as claimed in any of the preceding claims wherein the transmitting means each provides a wide angle beam of electro-magnetic radiation.
8. A shape sensor as claimed in claim 1 having one or more electro-magnetic radiation transmitters and one or more electro-magnetic radiation receivers, the transmitter(s) and receiver(s) being rotatable (either mechanically or electronically) is the diametrical plane of the annulus.
9. A shape sensor as claimed in any of the preceding claims wherein the electro-magnetic radiation transmitter(s) comprises a reflection or guide means for radiation disposed in relation tothe axis as aforesaid and a remote source of electro-magnetic radiation directed at the reflector/guide means.
10. A shape sensor substantially as described with reference to and as illustrated in the accompanying drawings.
CLAIMS New claims or amendments to claims filed on..........
Supersededclaims 1, 2.
New or amended claims:
1. A shape sensor for detecting the external shape of a member comprising means to transmit divergent beams of an electro-magnetic radiation at the member, a multiplicity of electro-magnetic radiation receiving means to receive the divergent beam, the receiving means being arranged in an annular array to receive therein the member the shape of which is to be determined, means to cause the transmitting beams to create individual divergent beams of radiation at a multiplicity of different positions around the axis of the annular array, means to detect the limits of the shadow caused by the member in each beam on the receiving means disposed opposite the transmitting means of the beam and means to compose from the multiple sets of limits of the shadows detected on the receiving means an image of the external shape of the member within the array.
GB08408084A 1984-03-29 1984-03-29 Shape sensors Expired GB2156514B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08408084A GB2156514B (en) 1984-03-29 1984-03-29 Shape sensors

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB08408084A GB2156514B (en) 1984-03-29 1984-03-29 Shape sensors

Publications (3)

Publication Number Publication Date
GB8408084D0 GB8408084D0 (en) 1984-05-10
GB2156514A true GB2156514A (en) 1985-10-09
GB2156514B GB2156514B (en) 1988-08-24

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0543912A1 (en) * 1990-08-17 1993-06-02 Strenk Scientific Consultants, Inc. Method and apparatus for r.f. tomography
WO2004043253A1 (en) * 2002-11-07 2004-05-27 Wisys Technology Foundation, Inc. Method and apparatus for producing an electrical property image of substantially homogenous objects containing inhomogeneities
WO2006095320A2 (en) 2005-03-10 2006-09-14 Koninklijke Philips Electronics, N.V. System and method for detecting the location, size and shape of multiple objects that interact with a touch screen display

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2069690A (en) * 1980-02-19 1981-08-26 Unitika Ltd Measuring dimensions of body
EP0039143A2 (en) * 1980-03-31 1981-11-04 Harmo Industries Limited Method and apparatus for determining the shape of objects
GB2087550A (en) * 1980-10-28 1982-05-26 Fish Farm Dev Ltd Apparatus for measurement of volume and related parameters
GB2133537A (en) * 1982-12-16 1984-07-25 Glyben Automation Limited Position detector system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2069690A (en) * 1980-02-19 1981-08-26 Unitika Ltd Measuring dimensions of body
EP0039143A2 (en) * 1980-03-31 1981-11-04 Harmo Industries Limited Method and apparatus for determining the shape of objects
GB2087550A (en) * 1980-10-28 1982-05-26 Fish Farm Dev Ltd Apparatus for measurement of volume and related parameters
GB2133537A (en) * 1982-12-16 1984-07-25 Glyben Automation Limited Position detector system

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0543912A1 (en) * 1990-08-17 1993-06-02 Strenk Scientific Consultants, Inc. Method and apparatus for r.f. tomography
EP0543912A4 (en) * 1990-08-17 1994-01-26 Strenk Scientific Consultants, Inc.
WO2004043253A1 (en) * 2002-11-07 2004-05-27 Wisys Technology Foundation, Inc. Method and apparatus for producing an electrical property image of substantially homogenous objects containing inhomogeneities
JP2006505352A (en) * 2002-11-07 2006-02-16 ウィシス テクノロジー フォンデーション インコーポレイテッド Method and apparatus for creating a substantially uniform electrical properties image of a subject including inhomogeneities
US7627362B2 (en) 2002-11-07 2009-12-01 Wisys Technology Foundation Method and apparatus for producing an electrical property image of substantially homogeneous objects containing inhomogeneities
WO2006095320A2 (en) 2005-03-10 2006-09-14 Koninklijke Philips Electronics, N.V. System and method for detecting the location, size and shape of multiple objects that interact with a touch screen display
WO2006095320A3 (en) * 2005-03-10 2007-03-01 Koninkl Philips Electronics Nv System and method for detecting the location, size and shape of multiple objects that interact with a touch screen display

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Publication number Publication date
GB2156514B (en) 1988-08-24
GB8408084D0 (en) 1984-05-10

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 20010329