METHOD AND DEVICE FOR DETERMINING THE MEASUREMENTS OF OBJECTS WITHOUT MAKING CONTACT THEREWITH

Abstract: A method and a device are disclosed for determining measurement data of objects, such as people who may be dressed, by means of ultrasonic waves, wherein ultrasonic waves being transmitted to objects are reflected and wherein the measurement data are determined on the basis of transmission time-related information contained in the received ultrasonic reflection pattern. A time window can delimit the received signal from other signals representing multiple reflections between object and clothing.

Description: METHOD AND DEVICE FOR DETERMINING THE MEASUREMENTS OF OBJECTS WITHOUT MAKING CONTACT THEREWITH The present invention relates to a method for determining measurement data of naked objects, such as people who may be dressed, by means of ultrasonic waves, wherein ultrasonic waves being transmitted to objects are reflected and the measurement data are determined on the basis of information contained in a received ultrasonic reflection pattern. The present invention furthermore relates to a device for determining measurement data of naked objects, such as people who may be dressed, by means of ultrasonic waves, which device comprises ultrasonic transmission means for transmitting ultrasonic waves to the object and receiving means for receiving a ultrasonic reflection pattern reflected from said object. A method and a device of this kind are known from JP-A- 52-3.436. Ultrasonic transmission means fitted with an ultrasonic wave oscillator for transmitting ultrasonic waves having a frequency of 10 KHz to the human body are used therein. A reflected ultrasonic interference pattern is deducted from the interfering waves reflected from the human body by means of arithmetic operations, whereby the distance to the human body is determined from the result on the basis of a phase difference change therein. One drawback of such a method and device is the fact that relatively complex arithmetic operations are required in order to arrive at the desired measuring result. The object of the invention is to provide an improved method and a simpler device, which make it possible to obtain measurement data of an object via less complex operations . In order to accomplish that objective, the method according to the invention is characterized in that said measurement data are determined from runtime-related information contained in the received ultrasonic reflection pattern. Accordingly, the device according to the invention is characterized in that said device comprises data- processing means connected to said receiving means for determining said measurement data from runtime-related information contained in the received ultrasonic reflection pattern. The advantage of the method and device according to the invention is that information with regard to the distance between transmission means and receiving means can be derived directly from the runtime, given the velocity of the ultrasonic waves, without having to carry out relatively complex operations. In one embodiment of the method according to the invention, a time window is used, within which the received ultrasonic reflection pattern is processed. In a corresponding embodiment of the device according to the invention, time window means are connected between the receiving means and the data processing means for admitting the received ultrasonic reflection during a certain time span only. The advantage of this is an even further simplification of the necessary arithmetic operations, because a correct setting of the time window will make it possible to ensure that the receiving means can only receive the ultrasonic main reflection which is relevant for the determination of the desired measurement data within the given time span. Thus, multiple reflections and interferences from ultrasonic waves which have been reflected one or more times between clothing and body and which confuse the main reflection, as it were, can be left out of the operations, simply because they do not fall within the time window. The desired measurement data can then be determined from the transmission time data of the main reflections. It has been established that the transfer characteristic h(t) of some of the clothing of people is such that, due to multiple internal reflections in the material of the clothing, the response to an ultrasonic wave reflected therefrom is not momentaneous but spread over time. The transfer characteristic is time-dependent in that case, and in order to determine the effect of reflection from this type of clothing, all partial reflections must be integrated in time. There will be a convolution connection between cause and effect in that case. In order to be suitable for this type of clothing as well, the received reflection pattern Φ effect / given the ultrasonic wave cause transmitted to the obj J ect, must be determined in dependence on time t from the convolution operation: t E ff ect < t ) = J Φ =a US e < * > h ( t - T ) d T - 00 Preferably, the receiving means are arranged for transmitting ultrasonic, puls wave shaped signals, so that the convolution operation, when used, can be a "spike" convolution operation, as a result of which the received ultrasonic reflection pattern can be detected more easily and more unequivocally than would be possible with the transmission of for example a pulse train. Envelope detection of the received ultrasonic reflection pattern by means of an envelope detector in the receiving means is preferred, because of the simple decision software and hardware that is required, in order to enable a quick determination of measurement data. Autocorrelation of the received ultrasonic reflection pattern appears to considerably improve the signal-to- noise ratio and thus the reliability of the method and device according to the invention. It has appeared to be possible to improve the accuracy of the measurement data by correcting said data for the temperature of the ambient air in which the ultrasonic waves propagate . The present invention and its further advantages will now be explained in more detail with reference to the accompanying drawing, wherein like elements are indicated by like numerals in the figures of the drawing. In the drawing: Figure 1 shows a schematic embodiment of a device according to the invention; and Figure 2 shows a simulation model of the device of Figure 1. Figure 1 schematically shows a device 1 which is arranged for determining the measurements of objects 0, such as (usually clothed) persons, by means of ultrasonic waves without making contact with said objects. Ultrasonic waves having a frequency of up to 100 KHz are reflected well from a human object, whilst they are not reflected too much from clothing or absorbed by said clothing. Device 1 comprises transmission means 2, which contain one or more ultrasonic transducers and receiving sensors 3 , which may or may not be separated from said transmission means 2, which receive the ultrasonic reflection pattern. Said transducers are capable of scanning the object, for example in a line scan, so as to carry out measurements on the entire object or on that part of said object which generally determines for example the size of people's clothing. The transmission and receiving means 2 and 3 may be combined into one transducer, which is capable of transmitting and receiving successively in a so-called pulse echo mode. An envelope detector (not shown) is present in the receiving means 3, in which detection takes place on the basis of the maximum of the received ultrasonic reflection pattern. Transmission means 2 which transmit a pulsed ultrasonic signal appeared to provide sufficient resolving power, which lies around 3.3 mm with a pulse duration of 20 μsec, which results in an eventual measurement deviation which is acceptable for clothing sizes. To this end, the measurement data are determined, on the basis of transmission time-related information in the received ultrasonic reflection pattern, in data processing means 4 of the device 1 which are connected to the receiving means 3. Given the velocity of the ultrasonic sound in air of about 330 m/sec, the distance travelled can be determined on the basis of the time which passes between transmission and receipt, from which it is possible to determine the distance between transmission/receiving means 2/3 and the reflecting surface of the object in the plane in which measurements are being carried out. When window, lock or gate means 5 are used, whereby the receiving means 3 are only sensitive during a certain time span, or for example only pass the received reflection pattern to the data processing means 4 during that time span, the received signal is not disturbed by signals being multiply reflected between clothing and object, as a result of which means 4 can remain relatively simple, the cost price can remain low and the processing time of the generally digitized signals can furthermore remain short . Because some types of clothing appear to exhibit a time- dependent transfer characteristic h(t) which does not react momentaneously, it takes some time on the side of receiving means 3 before all reflected signal contributions have been received. An integral operation is carried out in data processing means 4 for reconstructing the ultrasonic reflection pattern. The received ultrasonic reflection pattern Φ effect is then obtained by mathematical convolution of the ultrasonic wave Φcause transmitted to the obj •J ect and the transfer characteristic h(t) , according to the equation: t * effe = t ( ) = J Φ cauge (r ) h (t - r) dr (1) -00 Instead of using this convolution in the time domain, it is also possible to determine the corresponding integral transformation in the form of a product in the frequency domain, which is preferred if said computation can be realised more quickly by the software or if it requires less complicated hardware. When the transmitted wave Φ cauae is a pulsed signal, this signal can be regarded in a mathematical sense as a distribution, and equation (1) leads to a "spike" convolution, wherein Φ effect (t) will be equal to h(t) in accordance with the screening characteristic of distributions. For some other types of clothing, wherein no multiple internal reflections occurred, the transfer characteristic h simply appeared to be momentaneous , however. The pulsed signal may for example be a triangular signal, which preferably has a total duration of about 3 - 30 μsec, more in particular 20 - 25 μsec, in order to realise an optimum resolving power. It has become apparent that it is possible to improve the signal-to- noise ratio considerably by using autocorrelation techniques, which are known per se, in the data processing means 4. Device 1 preferably comprises memory means 5 and a temperature gauge 6 connected to memory means 5. Stored in said memory means 5, usually in the form of tables, are data relating to the sound velocity as a function of the temperature of the ambient air, wherein a signal P which is received from temperature gauge 6 and which is representative of the temperature measured by said temperature gauge is used as a pointer in said memory means 5 for selecting the associated precise speed of sound, in order to use it together with the determined transmission time in computing the measurement data. Figure 2 shows a simulation model of the device of Figure 1, wherein the transmission and receiving means 2 and 3 are arranged with transducers which each have a differentiating effect on the pulsed input signals supplied thereto. The effect is that the input signal supplied to means 4 in Figure 2 has been differentiated twice. By carrying out the inverse integration twice in means 4, a representative of the sought original triangular signal is obtained, whereby device 1 eventually appeared to possess very good noise reducing characteristics .

Claims: CLAIMS 1. A method for determining measurement data of naked objects, such as people who may be dressed, by means of ultrasonic waves, wherein ultrasonic waves being transmitted to objects are reflected and the measurement data are determined on the basis of information contained in a received ultrasonic reflection pattern, characterized in that said measurement data are determined from runtime- related information contained in the received ultrasonic reflection pattern. 2. A method according to claim 1, wherein a time window is used, within which the received ultrasonic reflection pattern is processed. 3. A method according to claim 1 or 2, wherein, in case of a time-dependent transfer characteristic h(t) of clothing of the object, the received reflection pattern Φ effecC / given the ultrasonic wave Φcause transmitted to the obj J ect, is obtained from the convolution operation: t Φ effect ( t ) = J Φ cause ( r ) h ( t - T ) άτ ( 1 ) . -00 4. A method according to claim 3, wherein the convolution operation is a "spike" convolution operation, wherein Φ oause (T) is a pulse wave shaped signal . 5. A method according to any one of the claims 1 - 4, wherein detection of the envelope of the received ultrasonic reflection pattern takes place. 6. A method according to claim 5, wherein detection takes place on the basis of maximums in the envelope of the received ultrasonic reflection pattern. 7. A method according to any one of the claims 1 - 6, wherein correlation techniques, in particular autocorrelation, are applied to the received ultrasonic reflection pattern. 8. A method according to any one of the claims 1 - 7, wherein the runtime-related information is corrected for the momentaneous temperature as regards the sound velocity of the ultrasonic waves. 9. A device for determining measurement data of objects, such as people who may be dressed, by means of ultrasonic waves, which device comprises ultrasonic transmission means for transmitting ultrasonic waves to the object and receiving means for receiving a ultrasonic reflection pattern reflected from said object, characterized in that said device comprises data-processing means connected to said receiving means for determining said measurement data from runtime-related information contained in the received ultrasonic reflection pattern. 10. A device according to claim 9, wherein said device comprises time window means connected between the receiving means and the data processing means for admitting the received ultrasonic reflection during a certain time span only. 11. A device according to claim 9 or 10, wherein said transmission means are arranged for transmitting ultrasonic, pulswave shaped signals. 12. A device according to any one of the claims 9 - 11, wherein said receiving means are arranged with an envelope detector for detection of the envelope of the received ultrasonic reflection pattern. 13. A device according to any one of the claims 9 - 12 , wherein said device includes correlation means, such as autocorrelation means, which are connected to said receiving means . 14. A device according to any one of the claims 9 - 13 , wherein said device includes memory means, wherein data are stored relating to the sound velocity as a function of the temperature of the ambient air. 15. A device according to any one of the claims 9 - 14, wherein said data processing means have a dual integrating character.

Inventors: LOESBERG PAULUS PIETER, LOESBERG, PAULUS, PIETER
Applicants: HECO MODE B V, LOESBERG PAULUS PIETER, HECO MODE B.V., LOESBERG, PAULUS, PIETER
Application year: 1999
Main classification: G01S15
IPC codes: G01S7, G01S15