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US 4,199,246 AGranted
Ultrasonic ranging system for a camera
AssigneePolaroid Corporation
InventorJuerg Muggli
Life of this patent
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AssigneePolaroid Corporation
InventorJuerg Muggli
Estimating the term…
An ultrasonic ranging system for a camera includes an ultrasonic transducer responsive to a keying pulse for transmitting a frequency modulated burst of ultrasonic energy toward a subject. The leading half of the burst is a chirp whose frequency varies from a higher to a lower value; during the trailing half of the burst, the frequency remains substantially constant. The system also includes a receiver for processing an echo signal produced by the transducer on receipt of an echo within a predetermined time interval following the burst, and producing a range signal with a characteristic linearly related to the distance of a subject being photographed from the camera. A variable Q filter in the receiver filters echo signals produced by the transducer eliminates the need for a matched filter. The filter Q has a relatively low value during the initial portion of said predetermined time interval causing the bandwidth of the filter to be wide enough to pass all the frequencies of the chirp returned from a subject relatively close to the camera. During the remaining portion of the interval, the Q increases narrowing the filter bandwidth and optimizing it, with regard to the signal-to-noise ratio, for the constant frequency of the burst returned from a relatively remote subject. This arrangement reduces sensitivity of the receiver to echo cancellation due to interference between waves reflected from a nearby subject without adversely affecting the signal-to-noise ratio for returns from remote subjects. An accompanying change in filter admittance reduces angular sensitivity of the receiver to off-axis echoes.
In a sonic ranging system including means actuatable for transmitting a burst of sonic energy toward a subject, for receiving and processing an echo from said subject, and for producing a range signal related to the range of said subject, the improvement comprising means for controlling said transmission means to produce a sonic burst having one portion varying in frequency and another portion of relatively constant frequency.
In a sonic ranging system including means actuatable for transmitting a burst of sonic energy toward a subject, for processing an echo from the subject within a predetermined interval of time following said transmission, and for producing a range signal related to the subject range, said processing means including a filter, the improvement comprising:
A sonic ranging system having means for producing a keying pulse, comprising:
A camera having a sonic ranging system for automatically focusing the camera comprising:
A camera comprising:
In a photographic camera including means for defining a focal plane, means for controlling the transmission of image carrying light rays to said focal plane from a subject to be photographed, means actuatable for transmitting a burst of sonic energy toward a subject, for receiving and processing an echo from said subject within a predetermined interval following said transmission, and for producing a range signal related to subject distance, the improvement comprising means for controlling said transmission means to produce a sonic burst having one portion varying in frequency and another portion of relatively constant frequency whereby said varying frequencies in said burst will produce an appropriate echo from relatively near subjects and said constant frequency will produce an appropriate echo for more remote subjects.
In a camera having actuable means for producing a film exposure in accordance with subject distance, and actuatable means for transmitting a burst of sonic energy toward a subject, for receiving and processing an echo from said subject within a predetermined interval following said transmission and for producing a range signal related to subject distance, the improvement comprising means for controlling said transmission means to produce a sonic burst having one portion varying in frequency and another portion of relatively constant frequency.
In a sonic ranging system including means actuatable for transmitting a burst of sonic energy toward a subject and for receiving and processing an echo from said subject so as to provide a time interval related to the range of said subject, the improvement comprising means for controlling said transmission means to produce a sonic multiple frequency burst with one frequency thereof being provided for a relatively short portion of said burst and another of said frequencies being maintained throughout at least a major portion of said burst whereby at least two frequencies may be relied upon to produce an appropriate echo from relatively near subjects and said other frequency alone may be relied upon for producing an appropriate echo from more remote subjects.
In a sonic ranging system including means actuatable for transmitting a burst of sonic energy toward a subject and for receiving and processing an echo from said subject so as to produce a time interval related to the range of said subject, the improvement comprising means for controlling said transmission means to produce a sonic multiple frequency burst with one frequency thereof being provided for a relatively short portion of said burst and another of said frequencies being maintained throughout at least a greater portion of said burst whereby at least two frequencies may be relied upon to produce an appropriate echo from relatively near subjects and said other frequency alone may be relied upon for producing an appropriate echo from more remote subjects.
Dependencies are inferred from the claim text.