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Uni Course > Control Précis 1 > Flashcards

Control Précis 1 Flashcards

1
Q

What is NON-Coherent light

A

Light caused by photons emitted in random directions

Different frequencies
Out of phase
Different coloured light

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2
Q

What is Coherent light /

Monochromatic light

A

Light where the photons are directed and emits on the same frequency

Mono - Single frequency

Same colour
Same phase

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3
Q

What Light will the Ruby Crystal alone produce if white light alone was used

A

NON Coherent light

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4
Q

Describe how a

RUBY CRYSTAL LASER

Works?

A

White light stimulates ions to E3/4

Heat is given of & drops to E2

Red light is emitted from E2 down to E1

Coherent light increases at the rate ions fall E2-E1

Population inversion accurs

But diminishes due to ions falling faster than white light can pump them up to E3/4

White light has to stimulate the process over again resulting in low energy pulses

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5
Q

Explain what is

Q- Spoiling

A

Technique to produce high energy pulses

Rotating prism is used instead of a mirror

Only when the prism is in alignment can LASER start

White light is switched on 350uS before alignment, to establish POPULATION INVERSION

LASER light will be reflected in the MW for 100nS

Power originated from a high energy flash tube as the white light source

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6
Q

Name some

LASER SAFETY

Precausions

A

Never look into the LASER

Beware of reflected surfaces

Use special Glasses

Get your eyes regularly tested

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7
Q

Frequency oscillation formula

A

Fosc = C/2🔺R

🔺R - delta range

±5= -2.5 . +2.5. Range is 5

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8
Q

Range formula

A

Te = transmit / receive

R = CTe/2

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9
Q

On a TLS, how is the

Range formula

Calculated

A

It measures the distance by sending a Pulse (Td) out

and reading the Time delay (Te)

between the received pulse (Td) back

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10
Q

Range Resolution / discrimination

Formula

A

Tr = Period of / cycle set by the system

🔺R = CTr/2

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11
Q

On a TLS, how is the

Range Resolution/Distortion

Calculated

A

The accuracy/ resolution/ distortion is determined by the FREQUENCY of the oscillator measuring the Time delay (Te) between pulses

Higher freq = higher accuracy in (1 meter intervals)

                   ±2m accurate

Lower freq = lower accuracy in (10 meter intervals)

                  ±20m accurate
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12
Q

Target resolution / discrimination

Formula

A

Td = width of LASER pulse

R = CTd/2

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13
Q

On a TLS, how is the

Target Resolution/ Distortion

Calculated

A

IOT avoid Target discrimination, which is 2 returning pulses so close to each other they overlap and look like 1.

                              _n_           Instead of.        _n_n_

Smaller Pulse width (Td) = less chance for return pulses to overlap

                                       Te > Td

Higher pulse width (Td) = more change for return pulses to overlap

                                     Te < Td
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14
Q

Tank LASER sight Min Range?

A

400 m

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15
Q

Tank LASER sight max range

A

10km

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16
Q

Why do we have a MIN range

A

Due to possible echoes that can reflect back and set off the counters

Giving false readings

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17
Q

What depends the MAX range for a Tank LASER

A

MAX range depends on the power of the received signal back

As range increases, the power reflected diminish until it cant be detected anymore. Which will be Max range

Pr = 2Pp.At.Al/Pi2.R4.02b

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18
Q

Why does spontaneous emissions produce NON-Coherent light

A

Because NON - Coherent light is caused by photons emitting light in random directions

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19
Q

On TLS

Why does the system require 2 counters?

A

Two required
One acts as a starting point where as the other one is reset when when a signal/ pulse is received back

Once the second ones counter is reset it counts to the end of its clock and switches everything off

The difference in counter readings will determine the distance

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20
Q

What is the function of the DUO-DIODE PUMP on the TLS?

A

Minimises noise and keeps the system amplified

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21
Q

What does the first/last switch do?

A

First - gives you a distance on the first pulse reading it receives back

Last - gives you a distance on the last pulse reading it receives back

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22
Q

With the aid of a graph explain the FIRST PULSE RANGING on TLS?

A

Draw a graph showing the 2 counters on a TLS with one lagging behind the other after receiving a Pulse echo, resetting and counting to 999 to shut everything down

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23
Q

Role of the 999 detector?

A
  1. Switches off the Rgate, stopping it from receiving any more pulses
  2. Switches off both counters when they reach 999, the difference being your distance
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24
Q

On TLS what are the first 3 thing that starts up?

P 1-18

A

(P 1-18)

  • PFN
  • System Dump 30sec
  • Prism motor drive
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25
Q

What is Visual Acuity?

A

The ability for the eye to distinguish between two points

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26
Q

What is Raster scanning ?

A

The process to scan picture lines, line by line

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27
Q

What is INTERLACING?

A

Where a picture is scanned in two parts

  1. Scan odd lines first
  2. Scan even lines after

When both field pictures are scanned, its called one frame.

28
Q

What is the difference between odd and even fields?

A

Interlacing takes place when

Odd fields gets processed first

Even fields gets Processed second

To make a full frame

29
Q

CCIR Video signal

Lines?

Frames?

Interlace?

Sync

A

Lines - 625 lines

Frames - 25

Interlace - 1:1

Sync - Sync Negative

30
Q

Name 2 Tv synchronisation types

A

LINE Sync

FIELD Sync

31
Q

Describe what Line Sync is?

A
  • All the horizontal picture lines, separated from each other by a Neg Pulse
32
Q

Draw a typical Line Sync pulse

And name the stages?

P1-22

A

(P1-22)

Front porch 1.55us - allows receive circuitry to settle

Sync pulse 4.7us - sync pulse

Back porch 5.8us - Fly past

33
Q

What is FIELD Sync?

A

Happens twice per frame

Once after the all the odd LINES were processed

Again after all the even LINES were processed

34
Q

What does FIELD sync consist of?

A

Start…

5 Pre-equalising pulses

5 Field broad sync pulses

5 Post-equalising pulses

25 line Field blanking period

Repeat…

35
Q

Draw a FIELD sync circuit?

Describe it…

(P 1-27)

A

(P 1-27)

LPF (low pass filter)

Denies LINE Sync pulses using the LPF, and allows through FIELD sync pulses

Remember( Low blocks Line)

36
Q

Draw a LINE sync circuit?

Describe it…

(P 1-28)

A

(P 1-28)

HPF (high pass filter)

Denies FIELD sync pulses, but allows through LINE sync pulses

Remember(Low blocks Line)

37
Q

Draw the Visual display unit

Describe the drawing in a few sentences?

(P 1-26)

A

(P 1-26)

  • Composite video signal comes in and get separated by a SYNC separator (LPF/HPF)
  • LINE sync pulses are smaller and more frequent than FIELD sync pulses!
  • LINE/FIELD both go into their own Scan Oscillators which Saw Tooth their pulses/waves
  • LINE pulse goes through a extra Pulse sharpener
  • The Composite Video signal is amplified before going into the Picture tube
38
Q

What is PIN CUSHIONING?

How can it be overcome…

A

Type of distortion in TV system which can be overcome using PERMANENT MAGNETS

39
Q

What is EHT Generation?

Draw a diagram (P1-32)

A

(P1-32)

  • The screen needs high Voltages to operate
  • Using already available LINE sync signals we can increase the Voltages desired by using a Diode multiplier
  • During a Pos(+) cycle D1 conducts and charges C2
  • During a Neg(-) cycle / FlyBack C1 charges from C2
  • Next Pos(+) cycle D3 conducts and charges C3
  • Next Neg(-) cycle / FlyBack C4 charges from C3
  • Hence the charge is pumped resulting in a 3X voltage increase
40
Q

How does a CRT scanning work?

(P1-29) Figure.7

A

(P1-29) Figure.7

  • Scene of view is focused onto a screen
  • an Electron beam scans the screen
  • The scanning is subject to different patterns of light causing more/less current flow
  • The change in current flow will be detected by the resistor
  • Which forms the Picture information in the form of a video signal
41
Q

a) What does equalisation pulses do?

b) What do post sync pulses do?

A

a) Ensure the video signal equalises and does not interfere with interlacing
b) Adds a blanking period allowing adequate time for completion of field flyback.

42
Q

Minimum and maximum range of a TLS ?

A

Max 10,000m

Min 400m

43
Q

Explain the function of the Sync Seperator

P1-26

A

(P1-26)

Sync separator separates the LINE/FIELD sync from the composite video signal

44
Q

Describe what the composite video signal is made up of.

And the process used to separate the signals once detected?

A

Negative going LINE/FIELD sync pulses.

Process is to use a LPF and HPF to separate the LINE and Field sync

45
Q

Night surveillance may be obtained how?

A

Active Illumination (AI) - active

Low light Television (LLTV) - cws sight / passive

Thermal Imaging (TI) - passive

46
Q

State a method for Active Illumination?

A

Illumination of infrared light source

Active system, prone to detection

47
Q

Low Light Television (LLTV)

Disadvantages?

A

CWS sight(passive) - which amplifies low light

  1. Insufficient on very dark night
  2. Too sensitive for daylight use
  3. Limited range
48
Q

Thermal Imaging

Disadvantages?

Advantages?

A

Passive system that picks up infrared radiation from all bodies higher than ZERO degrees.

Disadvantages:
- Thick fog or clouds can absorb our thermal image depending on how hot our target is

Advantages:

  • Operates on Darkest night
  • Good in Daylight
  • Good range
  • good in light haze/mist/smoke
49
Q

How does the weather effect the thermal imaging

A

Rain ,light haze mist and smoke has little effect on our thermal image

Thick fog or clouds can absorb our thermal image depending on how hot it is

50
Q

What is EMISSIVITY?

A

The Radiative Efficiency of a surface compared to a black body.

51
Q

Name the Thermal imaging term for the radiative efficiency of a surface compared to other surfaces?

A

Emissivity

52
Q

Name the requirements for a TOGS Lens?

A
  • Refractive Index (High)
  • Temperature Sensitivity (Low)
  • Hard surface (prevent abrasion)
  • Mechanical strength (prevents cracking)
  • Highly Transparent (related to wanted freq range)
53
Q

How is REFLECTIVITY a bad thing for a Lens?

A

When photons strike a medium (lens), the energy might get reflected known as the

REFRACTIVE INDEX

Higher index = less photons absorbed

to go into the lens and give a picture

Can overcome this by a Technique called BLOOMING

54
Q

What is BLOOMING and why is it used on a lens?

A

Blooming is a technique used to minimise the reflectivity of a lens.

On our Germanium lens a thin coating of Selenium is added

Germanium/selenium is in anti phase with the selenium/air interface canceling each other out

Improving the transmissivity (Photons passing through the lens)

55
Q

What is Optical A-Thermalisation and how can it be overcome?

A

The De-focussing of a lens due to temperature changes and the expanding & contraction of the lens

Compensate for changes in Temp by:

  • Manual adjustments
  • Auto servo adjustments
56
Q

How do we detect Thermal radiation?

A

By using a DETECTOR

Cadmium mercury telluride (Cd Hg Te)

57
Q

Why and how is the DETECTOR cooled?

A

By cooling the detector we dramatically reduce the noise which can mask our signal to acquire a thermal image

Using a:

JOULE-THOMPSON MINI COOLER

58
Q

Draw a diagram for the JOULE-THOMPSON MINI COOLER

And explain how it works?

P 2-11 (Figure. 8)

A

P 2-11 (Figure. 8)

  • Detector (Cd Hg Te) is mounted in a vacuum tube
  • High pressure (HP) Pure air is forced down a CRYOSTAT
  • At the end of the cryostat is a tiny ORIFICE releases the air and allows it to expand
  • Creating very low temperatures and cools the Detector
59
Q

Draw and explain via a Diagram

REMOTE DISPLAY

P 2-16 (Figure. 14)

A

P 2-16 (Figure. 14)

60
Q

Name 2 types of THERMAL IMAGER COMMON MODULE (TICM)

A

CLASS 1

CLASS2

61
Q

TICM

What is a CLASS 1 and CLASS 2 intended for?

A

CLASS 1:

  • DIRECT viewing
  • Batt powered using high powered gas for cooling

CLASS 2:

  • INDIRECT viewing
  • High pressure gas cooled
  • Display remote from TPU
62
Q

Draw a typical MRTD curve

P2-20

A

P2-20

MRTD-Minimal RESOLVABLE temperature differeance

Normally 0.1 degree C

63
Q

Draw and explain a typical MDTD curve?

P2-21

A

P2-21

MDTD-Minimal DETECTABLE temperature difference

64
Q

What is being tested by the MRTD test?

A

Tests for the MIN RESOLVABLE TEMP DIFFERENCE between two adjacent elements

65
Q

What is being tested by the MDTD test?

A

Tests for the MIN DETECTABLE TEMP DIFFERENCE between a target and its surroundings

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