The invention relates to sonic ranging and/or object detection systems, in general, and to such systems for aiding visually impaired persons, in particular.
Ultrasonic rangefinders for detecting the presence of or the distance to an object are well-known in the prior art. In, for example, U.S. Pat. No. 4,199,246 to MUGGLI, an ultrasonic rangefinder having a combination transmitting and receiving, capacitance-type, electrostatic transducer is incorporated in a photographic camera for the purpose of determining the distance to a subject and subsequently causing the adjustable focus lens of such a camera to be focused in accordance with a subject distance signal derived by said rangefinder.
In U.S. Pat. No. 4,280,204 to ELCHINGER, the disclosure of which is specifically incorporated herein, a conventional mobility cane for the blind incorporates ultrasonic object sensing apparatus in order to provide a blind, ambulatory cane user with the capability of remotely sensing the presence of movement-impeding obstacles within a spacial zone produced by said apparatus, whose size is infinitely variable. This sensing apparatus includes an adjustably mounted combination transmitting and receiving capacitance-type electrostatic transducer having an energy transmission pattern that approximates the size of said spacial zone.
The ultrasonic transducers described in the two above-mentioned patents transmit a directional, multiple-lobe pattern of ultrasonic energy whose contours are fairly well understood in the art. The multiple-lobe transducer pattern of a transducer with a circular backplate of 3.5 cm in diameter, for example, consists of a central lobe having a lobe angle of approximately 12.degree. at its half power point (-3dB) when operated at a frequency of 50 KHz, with said central lobe being generally symmetrical about a central axis and with a plurality of smaller magnitude side lobes that are also generally symmetrical about said central lobe axis. This electrostatic transducer, multiple-lobe pattern is described in much greater detail in an article by W. KUHL, et al., entitled "Condenser Transmitters and Microphones with Solid Dielectric Airborn Ultrasonics" in Acoustica, volume 4, 1954, pp. 519-532.
Lobe pattern shape of an electrostatic transducer of the type mentioned above is primarily a function of transducer operating frequency and transducer backplate diameter. The higher the operating frequency, the narrower is the central lobe angle and the lower the operating frequency, the wider is the central lobe angle. The central lobe angle of the object sensing apparatus disclosed in the above-mentioned ELCHINGER patent was purposely narrowed in order to provide a visually impaired person with a cue as to the direction of a particular detected object.
A disadvantage associated with sonic sensing apparatus of the type described, for example, in said above-mentioned ELCHINGER patent is the need to regularly move such sensing apparatus from side-to-side in order to provide a mobility cane user with directional information with respect to laterally positioned objects. Constant movement of a cane of this type can become tiring to a cane user as well as inconvenient to manipulate. Failure to so manipulate such a cane can result in the failure to detect a laterally positioned object and subsequent injury to a blind mobility cane user walking into such an object.
A primary object of the present invention is to provide apparatus for detecting the presence of frontally and laterally positioned objects that does not require the physical movement of said apparatus.
Another object of the present invention is to provide apparatus that can both determine the relative distance to frontally located objects and also detect the presence of laterally located objects.
A further object of the present invention is to provide a mobility cane for the blind that will enable a blind user to determine the presence of and relative distance to frontally located objects as well as determine the presence of laterally located objects.
Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings.