A hand-held instrument that would include an ultrasonic camera has been proposed as an efficient means of reading matrix symbols. The proposed instrument could be operated without mechanical raster scanning. All electronic functions from excitation of ultrasonic pulses through final digital processing for decoding matrix symbols would be performed by dedicated circuitry within the single, compact instrument housing.
The instrument (see figure) would be placed on a selected area on an object of interest believed or suspected to contain a matrix symbol (hereafter denoted, simply, the target). Intimate contact for the purpose of coupling of low-energy ultrasound would be ensured by use of either a flexible membrane camera face or a replaceable gel pad. Ultrasound pulses would be transmitted from a transducer, through the membrane or gel pad, into the target. A portion of each ultrasonic pulse, as modified by any matrix symbol present in the target, would be reflected through the membrane or gel pad to an ultrasound-imaging integrated-circuit chip, which would convert the resulting spatial variation of ultrasound pressure to voltages that could be used to construct a video image of the matrix symbol (if any).
A set of circuit boards above the ultrasound-imaging chip converts the output of the chip into a useful video format and would coordinate timing between the transducer pulses and the acquisition and processing of image data. The system is fully portable and battery powered. The instrument includes the following other boards:
- A pulser board would control the current pulses that drive the acoustic transducer.
- A board comprising a liquid-crystal display unit and its driver circuitry would enable display of the video image in the future. It could include a decoder board that would translate the video image of a matrix symbol into a recognizable set of binary data. This board would be identical to that used in a commercial barcode reader. Upon observing a matrix symbol in the video display, the operator would press a trigger switch to activate the decoder. The output of the decoder could be made available to a data-collection system for recording of the information in the matrix symbol.