DEPLOYANT – Luxury watch reviews & horological lifestyles – Luxury watch reviews & horological lifestyles
Ultrasonic scanning is not new. A familiar application would be ultrasound scan of an unborn baby, during which we would probably hear excited yelps when parents catch a glimpse of their child for the first time. The Scanning Acoustic Microscope uses this technique, and we use it to look at the crystal of the Bell & Ross BR V2-94.
An even earlier use, maybe the first ever use, are the bats. Bats make their own ultrasonic sounds to “ping” their path, then time taken for them to hear their own echo would tell them how far away a cave wall is.The physical concept is all the same- sending out a sound wave and detecting the time taken for an echo to be heard. The longer the time taken (time of flight) to hear an echo (reflected noise), the further away the wall is.
Acoustic scans of the Bell & Ross BR V2-94 Chronograph crystal
We reviewed the Bell & Ross BR V2-94 in great detail here. This is a Technical support article to explain the SAM in more detail.
Graphical representation of images from the Scanning Acoustic Microscope (SAM)
Graphical representation come in many forms, the most frequently used would be B and C scans. Here’s an overly simplified analogy. Say I have a double cheeseburger and I’m doing a scan with the probe on top of the burger. A B-Scan would have the probe move horizontally above the burger. At each point above the burger, it transmits an ultrasound which hits multiple surfaces such as the bun, the lettuce, and then the cheese and then the patty. With each surface that is further away from the probe, the echo takes a longer time to reach the probe. So the probe does this all the way along the top of the burger. Then the image produced would be as if we cut the burger in half with the components all stacked up.
For a C-scan, the probe will move in a snake pattern above the burger, until it fully covers the burger. This image would be a little complicated to imagine. In any one image, we first have to decide what’s the sound time of flight we want to focus on. So for a short time of flight, we will see an image with just a top view of the bread. And a longer time of flight, we will see the top view of the patty. The longer the time of flight being imaged, the further away is the image slice from the probe. But of course, this is just an analogy to visualize B and C scans. A detailed and scientific explanation can be found here. The main difference in this analogy to an actual scan is that the ingredients (materials) will actually absorb the sound, and the further we go, the less echo goes back to the probe. Also, with different materials, the speed of sound keeps changing and there are internal echos which affects the echo that ultimately reaches the probe.
So now that […]
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Article from: DEPLOYANT – Luxury watch reviews & horological lifestyles, by Sharon Tan
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