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Flashcards in Lesson 14 Deck (35)
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1

What are the 4 different componets to a transducer?

1. Lens
2. Matching layer
3. Single crystal element
4. Backing material
- damping

2

What are elements?

Crystals

3

What happens to beam profiles in transducers?

They go in and out at the same time
- no pulses

4

What is happening to beam width in pulse waves?

They are changing
- naturally shortens and widens again

5

Where is the natural focus on a pulse wave beam profile?

At the smallest point

6

Where is the near zone?

Between the focus point and the transducer
- minimun beam width

7

Where is the far zone?

From the focus point and onwards

8

What are 2 other names for the near zone?

1. Fresnel zone
2. Near field

9

What happens to the beam width when increasing distance from the transducer in the near field?

It decreases

10

Beam convergence

Light rays comes together (converges) after reflection and refraction at a single point known as the focus

11

What are 2 other names for far zone?

1. Fraunhofer zone
2. Far field

12

What happens to the bandwidth with increasing distance from the transducer in the far-field?

It increases

13

Beam divergence

When beams of light move away from each other after passing the focus point and going into the far field

14

Aperture

For a single disk transducer, this is the element size or width of group of elements
- opening
- top by the transducer

15

What does beam width change with?

Depth

16

What does beam width affect? (2)

1. Resolution of signal at that depth
2. Intensity of the sound beam at that depth

17

What happens to the resolution with a more narrow beam width?

It gets better

18

When is intensity the strongest?

At a smaller focus point

19

What is considered to be uniform?

Power
- equal at any point along the beam

20

What is the formula for beam width (Wb) at the focus?

1/2 the aperture size

21

NZL

Near zone length

22

What is NZL determined by? (2)

1. Size of the element
- aperture
2. Operating frequency

23

What happens to NZL if aperture increases?

It increases

24

What happens to NZL if frequency increases?

It increases

25

Is there a far zone length?

No

26

What happens to NZL if aperture goes up?

It goes up by 2
- aperture^2 proportional to NZL

27

What is the near zone length the same length is?

The focal length

28

What is a footprint?

Width of the probe

29

What do you need to do if you want a high frequency disk transducer to look at superficial structures?

Adjust the focus because intensity is highest at the focus and the resolution will be better

30

Do we want a large footprint or a small one when looking at smaller structures?

Smaller footprints because your NZL will be shorter and your focus will be higher