ULTRASONIC ABSORPTION MICROSCOPE 



CRYSTAL SPECIMEN 



THERMOCOUPLE 

 JUNCTION 



POWER 

 lAMPLlFlER 



JCOUPLING 

 1 UNIT 



SIGNAL 



GENE 



RATOR 



TEMPERATURE 

 SENSING ELEMENT 



HEAT EXCHANGE 

 UNIT 



SOUND 

 TANK 



KEYING! 

 I UNIT I 



DIGI 



AL 



TIMER 



|dc. amplifier 



|oscilloscope| 



Fig. 2. Block diagram of the electronic instrumentation of the ultrasonic absorption microscope. 



permits accurate duplication of the duration 

 of the acoustic pulse. A power amplifier 

 stage, driven by the signal generator, is used 

 to provide the power required to drive the 

 piezoelectric transducer. A coupling unit is 

 placed between the power emplifier and the 

 transducer element in order to obtain elec- 

 trical impedance matching. The electronic 

 driver system must be stable in frequency 

 and amplitude so that artifacts are not in- 

 troduced into the "picture." 



An example of the type of data obtained 

 at relatively low resolution using filament 

 models as test specimens is shown in Fig. 3. 

 Here, a nylon monofilament 0.003 inch in 

 diameter is moved in a plane between the 

 sound source and the probe (which has a 

 maximum dimension of 0.0005 inch in the 

 vicinity of the junction) starting from a 

 position in the field where its presence does 

 not appreciably influence the level of acous- 

 tic energy detected by the probe. The direc- 

 tion of movement is parallel to the crystal 

 face and perpendicular to the filament axis. 

 During this motion, the quartz plate is ex- 

 cited to radiate pulses of 12 mc/sec ultra- 

 sound with a duration of 0.1 sec. The ab- 



-20 +40 



RELATIVE DISPLACEMENT 

 (in units of 0.001") 



Fig. 3. The detection of the presence, in the 

 coupling liquid, of a 0.003 in. nylon filament bj^ 

 the ultrasonic microscope operating at a fre- 

 quency of 12 mc/sec. 



546 



