WO1998037434A1

WO1998037434A1 - Optoelectronic system for detecting space coordinates of an object

Info

Publication number: WO1998037434A1
Application number: PCT/EP1997/004178
Authority: WO
Inventors: Pietro Uberto
Original assignee: European Risk Capital Company S.A. Holding
Priority date: 1997-02-19
Filing date: 1997-07-31
Publication date: 1998-08-27
Also published as: IT1291037B1; TW339406B; ITTO970136A1; AU4378497A

Abstract

An optoelectronic system is described, for detecting space coordinates of an object, that comprises: a fixed transmission device, adapted to transmit a beam of electromagnetic radiation and composed of a plurality of transmitters placed on mutually different planes; a reception device placed onto the object, comprising a plurality of receivers placed on mutually different planes and adapted to generate signals indicating their own angular orientation with respect to the transmission device; and processing means that process received information from the reception device to detect space coordinates of the object.

Description

OPTOELECTRONIC SYSTEM FOR DETECTING SPACE COORDINATES OF AN OBJECT

The present invention refers to an

optoelectronic system for detecting space

coordinates of an object.

The applications for this system that are

known in the art cover several fields, the most common of which are multimedia applications that

employ computers, detecting systems for human bodies .moving into space and pointing devices for

computers .

The devices currently used in these fields have the following limits: - in multimedia applications, the devices are very costly because they use industrial sensors that are usually much more accurate than necessary

(accelerometers, gyroscopes, mechanical systems,

etc . ) ; - in detecting systems for human bodies moving

into space, mechanical arrangements are used that

are rather complex and costly to realize;

- in many cases it would be enough to have a low-linearity and low-accuracy device with only two degrees of freedom (for example the pointing system for a computer) .

Object of the present invention is solving the

above prior-art problems, providing an optoelectronic system that is simple to manufacture

and with a very low cost to detect the six space coordinates (three Cartesian coordinates and three

angular coordinates) of an object.

The above and other objects and advantages of the invention, which will result from the following

description, are reached with an optoelectronic

system like those disclosed in Claims 1, 3 and 5. Preferred embodiments and non-trivial variations of

the present invention are disclosed in Claims 2, 4 and 6 to 13.

The present invention will be better described by means of some preferred embodiments thereof,

provided as a non- limiting example, with reference

to the enclosed drawings, in which:

-- Figure 1 is a schematic view that shows the

general operating principle of the optoelectronic

system of the present invention;

- Figure 2 is a schematic view that shows the operating principle of an embodiment of the present invention ;

- Figure 3 is a schematic view that shows the operating principle of another embodiment of the present invention;

- Figure 4 is a block diagram of a first, possible practical arrangement of the

optoelectronic system according to the present invention;

- Figure 5 is a block diagram of a second, possible practical arrangement of the optoelectronic system according to the present invention;

- Figure 6 is a perspective view of a possible

embodiment of a receiver according to the present invention; and

- Figure 7 is a top view of the receiver in

Figure 6.

With particular reference to Figures 1 to 3 , the theoretical-practical operating principles of

the optoelectronic system of the present invention

will be described first, taking into account that this is anyway adapted to recognize the location of an object into space at different completeness and accuracy levels, even greater than the ones shown. The system operating principle is based on the directionality features of a detector or receiver

or on the receiver sensitivity being dependent on

the angle from which the signal to be detected

comes .

An example thereof is a directional microphone

having a characteristic cardioid shape, while a

photosensitive detector has a sensitivity of the

"cosine" type (proportional to the cosine of the

angle between signal propagation direction and

normal line to the sensitive detector surface) .

It is clear that, given a receiver with its

characteristic directionality and a signal

transmitter, by measuring only the signal intensity

detected by the receiver, there are not enough

information about the mutual position between

transmitter and receiver, since the received signal

amplitude can depend both on the direction from

which the signal comes (direction where the

transmitter is placed) , and on the distance at

which the transmitter is placed, and on the power

of the transmitter itself .

In order to get information related to the

mutual space location of a transmitter and a

receiver, different solutions can be used:

- move the receiver to search for the maximum sensitivity;

- multiply the transmitters by placing them in different points into space (in this case it is

necessary to know a priori the power of single transmitters) ;

- multiply the receivers by physically placing

them into the same centroid but providing them with a different space orientation (in this case it is

necessary to know the sensitivity of the different receivers) .

Taking into account this principle, in order to be placed in the three-dimensional space it is enough to have an adequate number of receivers and

transmitters: the relationship between them provides all searched information; if the number of transmitters/receivers is greater than the minimum enough one, a redundancy of information will be created that is useful to improve • knowledge of the position and to allow the system to operate even

when not all transmitters are in sight.

From the conceptual point of view, given a set of transmitters with singularly-known coordinates

for each one of them and univocally- identifiable emission for each one of them, it is possible, from a single receiver equipped with a sufficient number of elements, to obtain one's own space position

with six degrees of freedom (three Cartesian coordinates and three angular coordinates) , provided that the receiver receives the signal from a sufficient number of transmitters.

It is also important to note that, in

principle, it is possible to invert the role of transmitters and receivers since the operating

principle remains unchanged: it is always based on the measure of the relative transmitter-sensor angle notwithstanding the fact that the reference system is composed of transmitters and are the

sensors that moves into the space, or that instead are the transmitters that move into a space defined

by a set of receivers. Furthermore, it is not mandatory that the number of receivers and transmitters be the same since, provided that there are enough degrees of freedom, the system could operate even with a single receiver or with a

single transmitter, as will be better seen

afterwards .

The conceptual aspects on which the

optoelectronic system of the present invention is

based, will now be discussed. In short-distance communications, infrared devices are currently the most convenient technological solution even if it is obvious that the present invention can be applied also to

functionally-equivalent devices which will be available every time.

Let us therefore take into account the case of

a semiconductor photon detector like the well-known P-N junction silicon detector: by reverse biasing

it, the current crossing the junction, and therefore the useful electric signal, is proportional to the number of incident photons onto the detector, neglecting reflection losses as a first approximation.

With reference to Fig. 1, given a plane detector with area A and of any shape and given a source of parallel photons (ad ideal case is a

source located at an infinite distance, but practically it is enough that the. distance between

detector and source is much greater that the physical sizes of source and detector) that

generates a flux φ (photons/sec*area) , the electric signal S generated on the detector is proportional

to the cosine of the angle formed by the photon propagation direction and by the normal line to the detector surface (always neglecting reflection effects as a first approximation) , that is to the surface projection onto the normal plane to the photon propagation direction. The following equation therefore applies:

S = D ^• A ^• cos a ^• φ wherein :

S = electric signal

D = sensor sensitivity

A = sensor area

a = angle between normal line to detector surface and photon propagation direction φ = flux

If a linearly biased light source is now taken into account, instead of an ordinary light source, by providing the sensor with a polarizer, there occurs a signal depending on sensor rotation with respect to the axis that joins sensor and emitter,

that is this signal is proportional to the cosine of the angle formed between the incident light

polarization direction and the optical axis of the polarizing filter.

This allows earning one degree of freedom

without increasing the number of sensors- transmitters, and this can be convenient in particular applications that do not allow, for reasons of costs, rooms or the like, to use the so- far described standard technique.

Two theoretical techniques will now be described, that allow detecting an object

orientation on which photon flux detectors are located, with respect to a reference system

composed of a set of photon emitters (flux generators) without the need of knowing the value of flux φ , the sensor sensitivity D and the area A thereof .

The two described techniques are adapted to measure a single angle defined on a plane: this is

therefore a mono-dimensional problem. It will be seen below that, by multiplying the elements composing the system, it is possible to reach the knowledge of the six coordinates completely

defining a rigid body into the space.

The first theoretical technique of the system of the present invention will now be described. With reference to Fig. 2, the object being

examined is equipped with at least two detectors a,

b with the same area and sensitivity, having

respective normal lines Na and Nb and being placed

on two planes forming an angle β.

Taking into account a flux of photons normal to the line joining the two planes, the angle a

formed by the incident flux and the normal line Na to the detector a can be obtained by the following

equations : φ_Λ. = φ ^• Cos a φ_b - φ ^■ Cos (180 - (α + β) )

and therefore:

φ_λ/φ_h = Cos a / Cos { a + β) a is determined from this ratio, since angle β

is known by construction and the ratio of signals generated by the two detectors is measured.

In the simplest case, that is also shown in

Fig. 2, if the two detectors a, b are placed at a

right angle (β = 90°), the equation becomes:

φ_a/φ_b = Cos a / Sin a = Ctg a and therefore the angle a is univocally determined within a range of values by the ratio of signals on

the two detectors. It is clear that the ratio Φ_a/φ_b is determined only if both detectors are lit. It

can be thereby easily inferred that the theoretical maximum range for such a measuring system is equal

to the angle β formed by the two detectors a, b.

The second theoretical technique of the system

of the present invention will now be described.

With reference now to Fig. 3, let us take into account the case in which the object whose orientation has to be known, is equipped with only

one plane detector A and that the reference system

is composed of two sources a', b' that emit fluxes

having the same intensity and being incident on the detector A itself but not being mutually parallel .

Let us also take into account, always for reason of easiness as in case of Fig. 2, that the

direction vectors of the two fluxes and the normal line N to the detector A are on the same plane.

It is necessary that the detector is able to distinguish photons coming from the two emitters a', b', and this can be easily obtained by modulating fluxes and demodulating signals obtained

synchronously and asynchronously.

Having defined φ_a. , φ_b. the fluxes related to the two emitters a', b' picked up by detector A,

with reference to Fig. 3 and where K is a constant

that depends on the sensitivity and area of detector A, the following is obtained:

φ_a. = K ^• Cos a φ_b. - K • Cos (β - a)

from which:

φ_a. I φ_h. = Cos a / Cos (β - ex) Therefore, by the signal ratio and by the known value of β, the detector orientation angle is

univocally determined with respect to the reference system. Similarly to the previous case, angle β defines the range of angles wherein the system can operate: in this case, the maximum range is 180° - β.

What has been previously described refers to the measure of the orientation angle for an object

rotating around an axis: as already mentioned, by increasing the number of detectors and

transmitters, it is possible to know the orientation of an object into the three-dimensional space, that is the angular coordinates of the

object . If the transmitters are not placed at an infinite distance (real case) , the relative sensor- transmitter angle depends not only on the

object orientation into the space (the three Euler

angles) , but also on the Cartesian coordinates of

its optical barycenter: in this way the space position of the object is completely identified

with six degrees of freedom.

It can be therefore concluded that, within a

space lit by one or more radiation sources whose Cartesian coordinates are known, and by having available a body equipped with one or more sensors

whose relative orientations are known, it is possible, starting from signals detected by sensors, to compute the relative body- source angles and, from those, to compute the three Cartesian

coordinates and the three angular coordinates that

completely define the body itself in the reference system that is integral with the sources .

With reference to Figures 4 to 7 , two possible practical embodiments of the optoelectronic system according to the present invention will now be

described.

The described applications are related to the

two-dimensional case, that is to the case in which only two orthogonal coordinates has to be known, as occurs for example in a pointing device for computers .

The block diagram in Fig. 4 describes a first

practical embodiment of the system that can be used

with a number n of transmission devices and 1 reception device (or sensor-detector) . The system

in Fig. 4 substantially includes a driving circuit

1 that drives a transmission device composed of a plurality of transmitters (in this case Light Emitting Diodes or LEDs for visible, I.R. or U.V. light) 3, by successively turning them on and by adjusting their light emission intensity as function of the intensity signal coming from a synchronous demultiplexer unit 5, connected to the driving circuit 1 by means of an oscillator 6. This

unit 5 is connected to the reception device 7

through a preamplifier 9, and divides the signal from the reception device 7 into n signals related

to the n transmitters 3; moreover, the unit 5 generates a signal that is proportional to the total intensity to be sent to unit 1, as already

mentioned.

The effect of unit 5 is moreover that of

separating useful signals from background noise generated by other light sources being present in the environment .

Output signals from the demultiplexer unit 5

are supplied to a logic input circuit 11, that processes these signals and obtains coordinates x, y. Both coordinate signals x, y (for ease of representation, only the circuitry connected to signal y has been shown, being it identical with

the one connected to signal x) are input to a shunt

13, that computes the displacement "speed" of the

coordinates and supplies these data to a circuit 15 that computes the absolute value of direction B and to a circuit 17 that generates a clock signal C: the above-said signals B and C respectively represent amount and direction of cursor displacement on the monitor. These signals B and C are input to a logic managing circuit 19 (similar

to the one used by current mouses) , which in turn inputs signals, for example to a personal computer

(not shown) or to equivalent processing devices, for the processing thereof .

The block diagram in Fig. 5 shows a second practical embodiment of the system that can be used with 1 transmission device and a plurality (in this

case 4) of reception devices (or sensors- detectors). The system in Fig. 5 substantially comprises a reception device 21, that will be better described below, adapted to detect light emitted by a transmission device 23, that also in

this case has been realized by means of a LED. An input network 25, connected to the reception device

21 through a preamplifier 27, obtains the direction

coordinates x', y' from input signals from the

reception device 21 and supplies a signal Σ' that

is proportional to the total radiation intensity. These signals are sent to a synchronous demodulator 29, which extracts the coordinate signals x, y and

the sum (intensity) signal E from the background noise. This latter signal is sent to a driving circuit 31, connected to the synchronous demodulator 29 by means of an oscillator 32, that drives the above-mentioned transmitter device 23.

Quite similarly to the previous case, the coordinate signals x, y (for ease of

representation, only the circuitry connected to signal y has been shown, being it identical with

the one connected to signal x) are input to a shunt 33, that computes the displacement "speed" of the coordinates and supplies these data to a circuit 35

that computes the absolute value of direction B' and to a circuit 37 that generates a clock signal C: the above-said signals B' and C respectively represent amount and direction of cursor

displacement on the monitor. These signals B' and C are input to a logic managing circuit 39

(similar to the one used by current mouses) , which

in turn inputs signals, for example to a personal

computer (not shown) or to equivalent processing

devices, for the processing thereof.

With reference now to Figures 6 and 7, an embodiment of the reception device, for example 21 in Fig. 5, is shown in more detail. The reception device 21 is composed of a substantially pyramidal body, with as many faces as are necessary to guarantee required detections (in the Figure 4 faces are shown, forming a pyramid with a squared base) : every face 41 is composed of a

photosensitive element that operates as a real receiver element. Obviously, a plurality of

different arrangements are possible for the

reception device 21, both as regards the number of

pyramid faces, and as regards its generic space solid shape.

In addition to the above-described

applications, several uses of the optoelectronic system of the present invention are possible. The following are mentioned, as non- limiting examples: a) Pointing device for a computer, useful to

replace the so-called and well-known "mouse", to be

used by rotating the head in the direction where

the cursor must be moved: for this application, a

possible solution is a receiver-sensor device

shaped as a pyramid with triangular base or squared

base and one transmitter.

b) Recognition system for the space position

of the head (so-called multimedia virtual helmet) , wherein the processing computer can be informed about the helmet position with six degrees of freedom; this application has a possible solution through a sensor shaped as a pyramid with squared

or triangular base and a plurality of at least three transmitters. For reasons of completeness,

the system must also provide the possibility of "clicking" in some way, to be able to completely replace the mouse. Possible solutions are: (1) a

pedal, typically to be used in industries; (2) a voice recognition system, for household or office use or to help disabled people. c) Complete virtualising system for the

movement of a human body into the space: to realize

this solution, a suit is necessary, equipped with

polyhedric sensors at the ends of the body parts

within a reference system composed of a plurality

of adequately extended transmitters according to

the analysis completeness level that it is desired

to obtain.

d) Industrial applications, for example in the

field of deformation studies (crash tests, etc.) .

e) Helping devices for disabled people or for

professional use (object pointing, computer use,

etc.) that do not require using the hands. For its application versatility, the present invention can also be coupled to processing devices

that are more powerful that the currently known ones, that can be used instead of the above- mentioned personal computers or equivalent processing means. Particular reference is made to

neural networks, that are currently realized through software, but that in the future could be included in hardware devices suitable to highly improve performance and costs of the optoelectronic system of the present invention.

Claims

1. Optoelectronic system for detecting space coordinates of an object, said system comprising:

a transmission device (23), said transmission device (23) being adapted to transmit a beam of electromagnetic radiation;

- a reception device (21) placed onto said object, said reception device (21) comprising a

plurality of receivers (41), each one of said plurality of receivers (41) being adapted to generate signals indicating their own angular orientation with respect to said transmission

device (3, 23); and

- processing means (25, 29, 33, 35, 37, 39)

connected to said transmission device (23) and said reception device (21), said processing means (25, 29, 33, 35, 37, 39) processing information received

from said receivers (41) to detect said space coordinates of said object;

characterized in that:

- said transmission device (23) is placed in a fixed position; and

- said plurality of receivers (41) of which said reception device (21) is composed are placed

on mutually different planes.

2. Optoelectronic system according to claim 1, characterized in that said processing means (25,

29, 33, 35, 37, 39) substantially comprise: an input network (25) adapted to extract

direction coordinates (x¹, y') from input signals from said reception device (21) and to supply a signal (╬ú') that is proportional to the total radiation intensity;

- a synchronous demodulator (29) connected to

said input network (25) to extract the coordinate signals (x, y) and the intensity signal (╬ú) from a backgound noise;

- a shunt (33) connected to said synchronous demodulator (29) and adapted to compute the displacement "speed" of said coordinates (x, y) ;

- a circuit (35) connected to said shunt (33)

to compute the absolute value of the direction

(B-);

- a circuit (37) connected to said direction-

computing circuit (35) to generate a clock signal

⁽C⁾ ;

- a logic managing circuit (39) connected to

said direction-computing circuit (35) and said

clock-generating circuit (37) , said logic managing circuit (39) being adapted to send detecting signals for the object position to downstream processing devices .

3. Optoelectronic system for detecting space coordinates of an object, said system comprising: a transmission device (3) adapted to transmit a beam of electromagnetic radiation;

a reception device (7) placed onto said object, said reception device (7) being adapted to

generate signals indicating their own angular orientation with respect to said transmission device (3 ) ; and

- processing means (5, 11, 13, 15, 17, 19) connected to said transmission device (3) and said reception device (7), said processing means (5, 11, 13, 15, 17, 19) processing information received from said recepion device to detect said space coordinates of said object; characterized in that:

- said transmission device (3) is placed in a

fixed position, said transmission device (3) being composed of a plurality of transmitters, said plurality of transmitters of which said

transmission device (3) is composed being placed on

mutually different planes.

4. Optoelectronic system according to claim 3, characterized in that said processing means (5, 11,

13, 15, 17, 19) substantially comprise:

- a demultiplexer unit (5) connected to said reception device (7) and said transmission device (3), said demultiplexer unit (5) dividing the signal from said reception device (7) into n

signals related to the n transmitters (3) and generating a signal that is proportional to the total intensity;

- a logic input circuit (11) connected to said demultiplexer unit (5) and adapted to process said signals and extract said coordinates (x, y) ;

- a shunt (13) connected to said logic input

circuit (11) and adapted to compute the

displacement "speed" of said coordinates (x, y) ;

- a circuit (15) connected to said shunt (13) to compute the absolute value of the direction (B) ;

- a circuit (17) connected to said direction- computing circuit (15) to generate a clock signal

(C) ;

- a logic managing circuit (19) connected to

said direction-computing circuit (15) and said clock-generating circuit (17) , said logic managing

circuit (19) being adapted to send detecting signals for the object position to downstream processing devices .

5. Optoelectronic system for detecting space coordinates of an object, said system comprising:

- a transmission device adapted to transmit a beam of electromagnetic radiation;

- a reception device placed onto said object,

said reception device comprising a plurality of receivers, each one of said plurality of receivers being adapted to generate signals indicating their own angular orientation with respect to said transmission device; and processing means connected to said transmission device and said reception device, said

processing means processing information received

from said recepion device to detect said space coordinates of said object;

characterized in that: said transmission device ^ΓÇó is placed in a fixed position, said transmission device being

composed of a plurality of transmitters, said

plurality of transmitters of which said transmission device is composed being placed on

mutually different planes; and

- said plurality of receivers of which said

reception device is composed are placed on mutually different planes.

6. Optoelectronic system according to claim 3, 4 or 5, characterized in that it is equipped with modulating means for fluxes generated by said plurality of transmitters (3) and with demodulating

means for signals generated by said reception device (7) .

7. Pointing device for a computer, characterized

in that it is equipped with an optoelectronic system according to any of the previous claims, said reception device (7, 21) being placed onto said pointing device for a computer.

8. Pointing device according to claim 7, characterized in that said transmission device (23) is composed of a transmitter and said reception

device (21) is composed of three receivers (41) , said three receivers (41) forming the faces of a

pyramid with a triangular base.

9. Pointing device according to claim 7,

characterized in that said transmission device (23) is composed of a transmitter and said reception

device (21) is composed of four receivers (41),

said four receivers (41) forming the faces of a

pyramid with a squared base.

10. Multimedia helmet for the recognition of the head position into space, characterized in that it

is equipped with an optoelectronic system according to claim 3 or 4 , said reception device (7, 21) being placed onto said multimedia helmet.

11. Multimedia helmet according to claim 10, characterized in that said transmission device (3)

is composed of at least three transmitters and said reception device (21) is composed of three

receivers (41), said three receivers (41) forming

the faces of a pyramid with a triangular base.

12. Multimedia helmet according to claim 10, characterized in that said transmission device (3)

is composed of at least three transmitters and said reception device (21) is composed of four receivers

(41) , said four receivers (41) forming the faces of a pyramid with a squared base.

13. Suit for the detection of the movement of a human body into space, characterized in that it is equipped with an optoelectronic system according to any of claims 1 to 6 , said reception device (7, 21)

being placed onto said suit .