Abstract:
Ultrasound is used to determine, by echo ranging, the distance of objects in front of a user for allowing a visually impaired pedestrian to walk safely. A double circuit allows two simultaneous measurements. Distances measured are converted into human paces or steps. Then each ear of the human receives measurement information. The user can calibrate the apparatus for his or her own stride.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/482,682 filed Mar. 29, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to obstacle detection devices to be used by visually impaired pedestrians. More particularly, the present invention relates to an ultrasonic-based obstacle detection device. 
     BACKGROUND OF THE INVENTION 
     The task facing visually impaired pedestrians is the task of independently starting from a point and ending at a destination. This seems simple. However, it appears to be extremely challenging once the factors affecting mobility are taken into account. If one were to close his eyes and tried to move just a few steps, it would not take long for him to realize that the visually impaired have no access to basic information such as spatial orientation, the nature of the obstacles, the presence of moving objects, or even the boundaries of the path or travel surface. 
     Travelling aids have long been developed in efforts to allow visually impaired pedestrians to travel and move about safely and comfortably. One of the first versions and the most widely used up to the present is the long cane. Since the 1960&#39;s, several types of electronic travel aids (ETA) have been developed to improve the mobility of visually impaired pedestrians. Some of these devices are now currently available. The Russell Pathfinder provides one such example. It first came into use in 1965 and employs an ultrasonic beam to detect objects. It provides a vibrating warning that is inversely proportional to the distance. The Nottingham Obstacle Detector, designed in 1973, is a hand-held device that provides an auditory readout of the distance between the visually impaired individual and the object with eight musical notes. Recent technical development permits the use of a human voice to communicate the distance between the visually impaired individual and the object by a voice message. 
     U.S. Pat. No. 4,870,687 to Deleon discloses an oral readout rangefinder. It orally announces the measured distance by using of a speech synthesiser. U.S. Pat. No. 5,508,699 to Silverman discloses a dual sensing identifier/locator device for the visually impaired. It composes of two parts. Transmitters attached to a variety of objects send out coded signals to indicate the names of the objects. A receiver attached to the user decodes the signal and produces audible output that includes the name of the object and the distance. U.S. Pat. No. 5,347,273 to Katiraie discloses an ultrasonic detection system. It is basically a collision sensing system used by both automobiles and the visually impaired. For the visually impaired application, transducers are mounted on a cane. It gives the exact distance of an obstacle from the visually impaired using the device by a voice message. U.S. Pat. No. 5,724,313 to Burgess et al discloses a guide device using pitches and tones to inform the user of the nature of the obstacle. 
     All of these devices, some of which have been innovative in their own way, have serious deficiencies. They have often lacked functionality and compactness necessary for one who will use the device while walking. The distance information provided has often at best been impractical and at worst incomprehensible to a visually impaired individual. They generally have lacked the ability to adapt to the needs and characteristics of the visually impaired individual who will use the device. Thus, what is needed is a compact, functional device that readily adapts to the needs and characteristics of a visually impaired individual. A device which provides in a readily comprehensible and intuitive form information on the distance between a visually impaired individual and an object that person is approaching. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an ETA method and apparatus for a visually impaired individual that is economical and easy to use so that a visually impaired individual can safely move about on his or her own. 
     It is an object of the present invention to provide an ETA obstacle detection device and method for guiding visually impaired pedestrians in a safe, comfortable and easy manner. 
     It is yet another object of the present invention to provide an ETA method and apparatus which provides information on distance to an object in an intuitive manner which makes it easy for the visually impaired individual to easily and quickly understand the distance units and what they actually represent in their own experience. 
     It is yet another object of the present invention to provide an ETA with a method and apparatus which provides distance information in units of step or stride of an individual. 
     It is yet another object of the present invention to provide a means for the user to calibrate the apparatus to their own personal preferences or characteristics. 
     It is yet another object of the present invention to provide an ETA apparatus which is provided in an easy to use, compact and unobtrusive package. 
     The present invention provides an ETA apparatus and system which uses ultrasonic sound as a ranging medium with a dual channel transducer driver system to determine by echo ranging the distance of objects in front of a user of the ETA apparatus. The apparatus converts the information obtained from the time difference between an ultrasonic transmission and its subsequent echo to determine distance and it communicates the measure of distance to the user in measurements of normal human strides. The information on distance is presented to the user by pre-recorded statements of the number of strides or steps to the object or obstacle detected. 
     In a further aspect of the present invention, a twin channel transducer allows it to discriminate between objects that are on the left or right side of the path of travel of the user and to determine which is closer. 
     In yet another aspect of the invention information on distances and location of objects is provided to the user by a dual channel sound system that discriminates between objects or obstacles on the left or right of the user. The system, in its preferred embodiment, has ear phones for each ear which transmit the information by the left or right or both audio channels depending on the position of an obstacle or obstacles by sending an audio signal that is louder to the side that the an object is closer on as well as an audio distance message. 
     In yet another aspect of the present invention it incorporates the ETA of the present invention within the frame of glasses for the visually impaired pedestrian. The electronics is in a miniaturized configuration. 
     In yet further aspect of the present invention it provides a method and apparatus for the user to calibrate the distance of the stride used to measure and inform the user of distance to an object to the users preferred stride or step characteristics. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood by an examination of the following description, together with the accompanying drawings, in which: 
     FIG. 1 is the block diagram of the major functional components of the present invention; 
     FIG. 2 shows the detail of the core functional component of the present invention; 
     FIG. 3 is a perspective view of glasses that incorporate the present invention in one possible embodiment of the present invention; 
     FIG. 4 provides a flow chart that depicts the functional steps of the present invention; 
     FIG. 5 is the timing diagram of the major signal generated during operation of the present invention; and 
     FIG. 6 is one arrangement and use of the memory address that make up a memory of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The Overall Apparatus. 
     The invention works on the well-known principle of range and direction finding with reflected ultrasonic sound waves in a fashion similar to the operation of radar and sonar. The ultrasonic travel aid of the present invention allows the measurement of distance between two points by emitting a short burst of high frequency sound waves and listening for an echo. When the echo is received, the time elapsed between the outgoing and reflected sound pulse is measured. Knowing the speed of the sound wave and the time taken to travel, the distance from the emission point of the ultrasound to the object can be calculated by the formula: D=(S×T)/2, where D stands for half the total distance traveled, S for the speed of sound wave and T for the time elapsed. D, in the present invention being the distance from the point of generation of the ultrasound burst to the object which created the echo of the ultrasound burst received. 
     Ultrasound essentially means “high frequency sound.” The frequency range of ultrasound is from twenty to five hundred thousand vibrations per second, too high for human beings to perceive. It was chosen as the transmission medium over other mediums, such as light or radio waves or lower frequency sound waves because of its unique characteristics. Sounds at higher frequencies are more directional and focused than lower frequency waves. Ultrasonic waves can also be focused much like a beam of light. Therefore, an obstacle will more strongly reflect a beam of ultrasound waves than lower frequency sound waves. Because of its relatively slow speed of propagation, it is easy to detect. Furthermore, the ultrasonic sensor, a device that transmits ultrasonic pulses and receives the reflected echoes, can withstand extremely harsh environments, making it more suitable for outdoor applications. 
     Since the visually impaired are unable to read visual display, audio is the most efficient way to communicate information to the user. Musical notes have long been used to represent distance. Many ETAs also use vibrations where the intensity of the vibrations warns the user of the range between him and the obstacle. However, these methods leave the visually impaired user to translate notes or vibrations into an understanding of the distance. This is ineffective and often leads to confusion or worse for the visually impaired user. 
     One of the objectives of the present invention, the ultrasonic travel aid, is to improve the presentation of information, a common shortcoming of ETAs up to now. The new method uses state of the art technology to present distance in human voice. If the distance is given in either meters, feet, inches etc. most person especially the visually impaired still have difficulty in conceptually understanding units of measure expressed in this form. Therefore, an artificial intelligence is added by presenting the units of distance in steps or strides corresponding to the length of the user stride. The length of one&#39;s own step or stride is a unit that everyone can comprehend without difficulty. This is particularly true of the visually impaired, many of which have had such impairment from birth and thus have a greater conceptual difficulty in translating distance measurements into something understandable. 
     As depicted in FIG. 1, a block diagram of the major functional parts the present invention, the ultrasonic travel aid consists of four major functional parts: a Logic Control module  23 , an Ultrasonic Generation module  25 , a Distance and Direction Discrimination module  24 , and an Information Presentation module  22 . The invention has a fifth component a Calibration module  33  which, as will be explained below in detail, is used to adjust the unit to the personnel stride or step characteristics of the individual user. 
     The Ultrasonic Generation module  25  has two sub-components composed of two parts each. A left ultrasonic driver  27  which drives a left ultrasonic transducer  31  and a right ultrasonic driver  26  which drives a right ultrasonic transducer  30 . When commanded, the right  26  and left  27  ultrasonic drivers produce in their respective ultrasonic transducers  30  and  31  burst of ultrasonic sound. Likewise, when the transducers  30  and/or  31  receive a return echo, they communicate receipt of this echo to their respective ultrasonic driver. Having a separate circuit and transducer for the right and left side allows the system to determine which side the object being approached is on or if it is across the entire path of the user. 
     The ultrasonic drivers  26  and  27  are controlled by and communicate with the Logic Control module  23 , which sends the signal that instructs each ultrasonic driver  26  and  27  to emit periodic bursts of ultrasonic sound through their respective transducers. In turn, when the ultrasonic transducer  30  or  31  receives an echo, they communicate this event to the Logic Control module  23 . If, as will be discussed in detail below, the echo is received within the requisite period of time, the Logic Control module will generate a STOP LEFT or STOP RIGHT signal to their respective ultrasonic driver  26  or  27 . 
     The Distance and Direction Discrimination module  24 , depicted in detail in FIG. 2, consists of a Distance-Base Generator  60 , a left channel Distance Counter  61  for the left ultrasonic driver  26 , and a right channel Distance Counter  62  for the right ultrasonic driver  27 , a Distance Extractor  63 , and a Directional Information Generator  64 , etc. sub-components. This module is also controlled by the Logic Control module  23 . Upon receiving the START signal, the Distance-Base Generator  60  starts to generate pulses. In the meantime, the left and right channel Distance Counter  61  and  62  start to count distance-base pulses. Upon receiving a STOP LEFT or STOP RIGHT signal, the corresponding counter will stop counting. The counted number of pulses is proportional to the distance between the obstacle and the sensor. 
     The Distance Extractor  63  determines which obstacles detected by the dual ultrasonic driver is closer to the user. To do this, it compares the dual distance counter  61  and  62  outputs, taking the smaller one, representing the obstacle closer to the user. In the preferred embodiment of the present invention outputs from the dual distance counters  61  and  62  (the dual distance counters in the preferred embodiment will most likely be clocks or similar appropriate device) will be normalized by a preset value that represents the largest distance the sensor can measure. The normalized distance being the maximum distance that the unit is set to detect objects. Standard transducers that would function with the present invention have a range of about 20 to 30 meters. However, the normalized distance in the preferred embodiment is about 10 meters a distance equivalent to roughly 30 to 33 steps or strides by the average individual. 
     Referring back to FIG. 1 the Information Presentation module  22  is made up of an Information Presentation Interface  28  that drives a right audio channel driver  36  and audio output  34  and a left audio channel driver  37  and audio output  35 . The two separate audio channels, one for each ear, plus the corresponding left and right ultrasonic transducers give the apparatus and system of the present invention the ability to distinguish which side an object sits on or if it sits across the entire path the individual user. 
     FIG. 3 depicts how the glasses  39  of the preferred embodiment of the present invention might appear. The most notable features would be the left  27  and right  26  transducers. Left  35  and right  34  audio output devices, in the preferred embodiment would be typical small earphones, which the user would insert into each ear. The remainder of the electronics that makes up the invention would be typical miniaturized built into temple supports  40  and  41 . Actual electronic parts have not been identified for the functional parts enumerated with respect to FIGS. 1,  2  and  3  since those skilled in the art, once they understand the concepts enumerated herein will be able to obtain the necessary parts to fabricate the present invention without any difficulty. 
     Operation of the Invention: 
     FIG. 4 provides a flow diagram that depicts the overall operation of the system of the present invention. In the preferred embodiment every two seconds, the Logic Control module generates a START signal that will allow the Ultrasonic module to emit a burst of ultrasonic waves  42 . The transducers  30  and  31  then listen for returning echoes  43 . In the meantime, this START signal is also sent to the Distance and Direction Discrimination module  24  to start counting distance-base pulses  42 . 
     Upon detecting an echo, the Ultrasonic module sends out an ECHO received signal  44  which is then passed on to the Logic Control module  23  to generate a STOP LEFT or STOP RIGHT signal. These STOP signals are passed to Distance and Direction Discrimination module  24  to stop counting pulses  46 . The Distance and Direction Discrimination module  24  then counts the number of pulses generated by the timing mechanism between the START signal and the signal to stop timing  47 . The Information Presentation module  28  then reads out the number of pulses counted between the START and STOP signals and determines the distance in strides  48 . This information is then transmitted to the user in the form a human voice  49 . When there is no echo being detected within the maximum normalized time period  45 , the Logic Control module will generate a STOP signal to stop timing  47 . 
     FIG. 5 provides a timing diagram with the major signals generated during normal operation of the present invention. The system first generates a START signal  53  which initiated generation of ultrasonic pulses by the transducers and the commencing of the timing or distance count  56 . Commencing of the distance count involves commencing of the timing pulses  56 A. A periodic reset signal  57 , generally one every two seconds, commences the start or START signal  53 . Upon receipt of an echo, an ECHO signal is received which halts the timing sequence  56  and generates a sound enable signal. When there is no echo received within the maximum normalized time period, a STOP signal is generated to halt the timing sequence  56 B. 
     Presentation of Distance as Strides: 
     The ultrasonic travel aid does not directly measure the distance to an object. Instead, it measures the time taken for the ultrasonic waves to make a round trip from its transducer  30  and  31  to an object and back again. Therefore, knowing the speed of ultrasound and the time taken to travel for a round trip, the distance between the user and the object can be calculated using the formula: D=(S×t)/2, where t is the time elapsed between the START and STOP signals. 
     We know that the speed of ultrasound is approximately 343 m/s, which implies that is takes ultrasonic waves approximately 6 milliseconds to travel one meter for a round trip. If we can generate pulses at 6 milliseconds per cycle, then, by counting the number of pulses between START and STOP signals, we would know the distance in meters immediately. 
     As mentioned above, it is difficult for the visually impaired to comprehend distance in meters. Hence a little “artificial intelligence” is added. The distance is given out in the form of steps. For example, it takes ultrasonic waves approximately 2 milliseconds to travel 0.343 meters in round trip, which is approximately the length one step of an adult. Consequently, if we turn the distance-base generator  60  to generate pulses at two milliseconds per cycle, we would know the distance in steps instead of meters. This time base can be easily calibrated to suit the user with different length of step. 
     One of the unique features of the present invention is the presentation of distance by the human voice. State of the art static recorder chip is used to convert the number of steps into human voice. The information presentation module  28  can be a standard static recorder chip that allows the recording of messages onto the chip for played back at any time. Around thirty messages were to be recorded, and a systematic procedure was derived to allow messages to be played back with as little delay as possible. 
     Two methods are possible. The first being message cueing to a recorded message. This proved to be difficult for the delay was too long in order to skip messages. The second method involved accessing a recorded message by a specific address. The standard static recorder that can be used contains six hundred addresses with a total duration of sixty seconds. This means that one second of recording time is equivalent to ten address counts. If each message lasted 1.6 seconds, it could be stored in the space of sixteen addresses. Since sixteen is an “even” binary multiple, we can ignore all the counts less than sixteen by strapping the corresponding bits to ground and programming the remaining bits. This simplifies the design tremendously, because the address of messages stored in the chip are directly related to number of steps, as shown in the table at FIG.  6 . In this way, the number of steps measured by Distance and Direction Discrimination module  24  can directly access the voice recording of “n steps”. 
     Calibration: 
     The present invention includes a means to calibrate the apparatus to the individual stride or step characteristics of the user. To calibrate the present invention, the user simply activates the calibration module  33  of FIG. 1 with control  79 . The user takes a predefined number of strides, for example, four strides, away from a wall. Then, he or she will turn and face the wall. The user then places the apparatus in the calibration mode, which will measure the distance between the user and the wall in term of number of clock cycles. When the user pushes the confirmation button, the unit then determines the number of pulses equivalent to the average stride of the user calibrating the device. This information is stored on the system as a reference to generate the distance-base pulse that will be used to measure the distance in strides or steps. 
     An Additional View of The Invention: 
     As noted above the present invention as depicted in FIG. 1 is an obstacle ranging system for visually impaired pedestrians comprising a Dual Sensing module  25 , a Distance and Direction Discrimination module  24 , a Logical Control module  23 , an Information Presentation Interface  22 , a Distance-Base Generator module (which in the preferred embodiment forms part of the Distance and Direction Discrimination module  24  or Logical Control module  23 ), and a calibration module  33 . 
     The Dual Sensing module  25  comprises two ultrasonic drivers  26  and  27 . The ultrasonic driver transmits a burst of ultrasonic signals when it receives the START command and listens for echoes. When the ultrasonic driver receives echoes from the obstacle, it sends out an ECHO signal. The two channels of the Dual Sensing module  25  operate independently of each other and the system of the present invention is able to process the information from each channel separately and determine if two different objects are on the left and right side of the path of the user are at different distances from the user and which is closer to the user of the invention. 
     The Distance-Base Generator module  60  in the preferred embodiment is incorporated in the logical control module or the distance and direction discrimination module. However, it could be separately configured without too much difficulty. The purpose of the Distance-Base Generator module  60  is to generate step-time base pulse  56 A and  56 B of FIG.  5 . It comprises a crystal clock generator and a counter. When it receives a START signal from the Control Logic module  23 , it begins to generate Distance-Base pulse. It uses the step length (number of crystal clock cycle) stored in the calibration module as a reference. The reference has been set during the calibration mode. The reference is a measure of the average stride of the user. When the crystal clock cycle reaches this number, it generates a distance pulse. When it receives the STOP LEFT and STOP RIGHT signals from the Control Logic module  23  when the Control Logic module  23  receives and echo signal from either ultrasonic drivers  26  and  27 , it resets the distance generation counter. It should be noted that this process occurs separately for each ultrasonic driver allowing the system to discriminate between information received from each channel of the dual sensing module  25 . 
     The Distance and Direction Discrimination module  24  is the core of the invention. This module includes a Distance-Base Generator  60 , a Dual Distance Counter  61  and  62 , a Distance Extractor  63  and a Directional Information Generator  64 , etc. sub-components. When the Control Logic module sends out the START signal to the ultrasonic module, the Distance-Base Generator  60  starts to generate pulses. In the mean time, the Dual Distance Counter  61  and  62  also start to count the number of distance-base pulse. When the module receives the STOP LEFT or STOP RIGHT signals, the corresponding distance counter  61  or  62  stops counting. The counted number of distance-base pulses is proportional to the distance between the obstacle and the sensor. 
     The Distance Extractor  63  determines which obstacles detected by the dual ultrasonic driver is closer to the user. To do this, it compares the Dual Distance Counter  61  and  62  outputs, taking the smaller one representing the object closer to the user. In the preferred embodiment of the present invention, outputs from the Dual Distance Counter  61  and  62  will be normalized by a preset value that represents the largest distance the sensor can measure. As noted the preferred embodiment of the present invention has a maximum range of 20 to 30 meters; however, as a practical matter the actual range in the preferred embodiment is normalized to a maximum of 10 meters, anything beyond this distance being indicated by the system as beyond range. The information presentation module uses the output of the normalized counter number in presenting the information on distance to the user of the system. 
     The control logic means control of the operation of the talking glasses. The flow chart of FIG.  4  and the timing diagram of FIG. 5 indicate the procedure it uses for control and operation of the system. It first sends out a START signal that will start the Dual Ultrasonic Driver module  25 , start the Dual Distance Counter  61  and  62 , and reset the static recorder and an internal step down counter. When it receives an ECHO signal from the ultrasonic driver module, it will stop the corresponding distance counter. When it receives both ECHO signals from the dual ultrasonic driver, it sends out a signal to the Distance and Direction Discrimination module  24  to start the process of determining the distance to the object or objects which side are they on etc. When the module stops processing, it sends out a signal to the Information Presentation module  22  to present the information to the user based on the information provided to the information presentation module by the Distance and Discrimination module. 
     The information presentation module can be best understood by FIG.  1  and FIG.  3 . It has two parts, an audio generation part and what amounts to a 3-D surrounding sound generation part or more correctly left and right sound channels. The audio generation part contains pre-recorded information, such as “one step”, “two steps”, and “three steps”. . . This information is stored using a static recording technique and it can be accessed by index by standard procedures well known in the industry. Thus, the number of steps can be used directly as audio information index. It should be noticed that when the distance is too far, for example, excess the possible distance that ultrasonic driver can measure or is beyond the normalized range, the audio output is “too far”. However, when the distance is too close, for example, less than one step, the audio output will be “too close”. The second part is to use of the left channel right channel audio out put to present the direction information. When an obstacle on the left hand side is closer than an obstacle on the right hand side, the left hand side audio output will be more pronounced or louder than the right hand side audio output. The normalized distances for both left hand side control the depth of field or range and right hand side as described above. 
     The calibration module  33  as depicted in FIG. 1 has a control  79  in the preferred embodiment a push button. The calibration module  33  also has a distance input and means to store the step length pertaining the user. The clock generator of the system generates the time base input. When the device is first powered, a predefined number of time bases corresponding to the length of one step are loaded into the step length memory. When the user pushes the calibration button the system of the invention is in the calibration mode. It measures a predefined number of steps, for example, four steps. The number of time bases corresponding to the length of one step will be calculated and stored in the step length memory which will be used as the reference to convert the distance measurement into number of steps. 
     While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and detail may be made to it without departing from the spirit and scope of the invention.