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SPRING 2024: Principles II > UNIT 3: Digital Display Characteristics & QC > Flashcards

UNIT 3: Digital Display Characteristics & QC Flashcards

1
Q

Steps in Digital to Analog conversion

A
  1. Coding
  2. Quantization
  3. Sampling
  4. Scanning
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2
Q

Do we need to see the image in Digital or Analog form?

A

Analog form

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3
Q

Two processes in which image data is formatted to fit a display monitor

A

Decimation and Interpolation

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4
Q

Formatting for display: Decimation

A

Image data is larger than monitor matrix size
-Information is sampled
-Some detail is lost

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5
Q

Formatting for display: Interpolation

A

Image data is smaller than the monitor matrix size
-Information is combined and averaged to fill in empty pixels
-Image may become blurry

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6
Q

Primary vs secondary display

A

Primary: Radiologists monitor
Secondary: Radiographers work station

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7
Q

Soft copy viewing LCD monitors: LCD with Cathode Backlight

A

• Monitor sizes are limited
• Lower initial cost
• Shorter lifespan
• More popular

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8
Q

Soft copy viewing LCD monitors: LCD with Light Emitting Diode(LED)

A

• Monitors can be customized
• Longer Lifespan
• Higher initial cost
• Superior image quality

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9
Q

Layers in the LCD monitor

A

-Backlight
-Polarized filters
-TFT layer
-Liquid Crystal layer

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10
Q

Backlight

A

Providing light for monitor

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11
Q

Polarized filters

A

Hold liquid crystal material in place

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12
Q

TFT layer

A

Send/Apply electricity current to liquid crystal layer

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13
Q

Liquid Crystal layer

A

Material used to create image on monitor, allows varyinf amounts of light to pass through it

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14
Q

Monitor characteristics: Resolution

A

Controlled by matrix size

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15
Q

Monitor characteristics: Luminance

A

Brightness produced at the monitor

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16
Q

Monitor characteristics: Contrast

A

The differences between adjacent areas of IR exposure on the image

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17
Q

Monitor characteristics: Bit Depth

A

Quantity of shades of gray the monitor displays

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18
Q

Monitor characteristics: Uniformity

A

Even exposure throughout the image in the absence of any attenuating materials

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19
Q

Monitor characteristics: Glare

A

Occurs when too much ambient light scatters around an object making the image appear “washed out”

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20
Q

How is viewing the digital image affected by the inverse square law?

A

Luminance decreases as you increase distance from the monitor

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21
Q

How is viewing the digital image affected by the Cosine law?

A

when the monitor is viewed from an angle both the contrast and luminance is reduced

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22
Q

Cosine law

A

Angular dependence. The best viewing angle of a digital display device is straight on.

23
Q

Grayscale Standard Display Function (GSDF)

A

a DICOM standard to provide a consistent appearance of grayscale between displays

24
Q

Perceptual Linearization

A

equal changes in digital values result in equal changes in perceived brightness values

25
Q

QC test patterns used in display monitor performance tests

A

-SMPTE
-TG-18 (AAMP)

26
Q

What is a photometer used for?

A

-Luminance meter
-Test for brightness emitted from the monitor

27
Q

Monitor and Display system QC

A

Brightness
Contrast
Resolution
Distortion
Reflection
Angular Dependence

28
Q

Monitor quality

A

•Resolution
•Luminance
•Contrast
•Bit Depth
•Uniformity
•Glare

29
Q

SMPTE Image

A
30
Q

TG-18 (AAPM) Image

A
31
Q

Hard copy images

A

-Refers to images in a form that can be touched
-Examples: Paper, Film

32
Q

Hard copy devices and storage media

A

-Paper (thermal) printers or film (laser) printers
-Hard storage disks, such as DVD or CD’s, or SSD such as Flash media

33
Q

Soft copy images

A

Images that can only be seen. Terms that refer to soft copy devices include:
a. Monitors
b. LCD or CRT
c. Display
d. Medical display

34
Q

Before the latent digital image can be viewed on a monitor it must undergo

A

Digital to Analog Conversion

35
Q

Information to Image transformations

A

The algorithms used to take input digital data and produce output in a form of an analog image

36
Q

T or F: all soft copy displays emit a light signal in an analog form for humans to be able to see the image

A

True

37
Q

Lumen

A

The basic unit of light intensity

38
Q

Luminance

A

a measurement of the amount of lumen or brightness emitted onto an entire viewing area, such as a digital display

39
Q

Advantages and Disadvantages of LCD monitor

A

Advantages of LCDs:
• Lower energy consumption
• Lighter and thinner
• Less heat produced (especially LED backlit models)

Disadvantages of LCDs
• Angular dependence: loss of contrast at larger viewing angles
• Images not as bright and color reproduction not as good as CRTs

40
Q

Advantages and Disadvantages of CRT monitor

A

Advantages of CRTs:
• Very bright images even at greater viewing angles
• Very fast refresh rate (# of times the screen refreshes per second) – produces less blur in dynamic imaging

Disadvantages of CRTs
• High energy consumption
• Higher heat production
• Large (deep) and heavy

41
Q

Matrix

A

an array of pixels arranged in columns and rows

42
Q

Decimation or sub-sampling is used when the input matrix size to too _______ for the output device matrix

A

large

43
Q

Interpolation is used when the input image matrix is too _______ for the output device matrix.

A

Small

44
Q

What are the two types of luminance meters?

A

• Near-range – used in close proximity to the surface of the display
• Telescopic – used to test from a distance of 1m

45
Q

Types of Test Typically Performed:

A

• Geometric Distortion
• Reflection
• Luminance response
• Luminance non-uniformity
• Display Resolution
• Display Noise

46
Q

Geometric Distortion

A

size and shape of the displayed image is different from the original (acquired) image

47
Q

Reflection

A

ambient light interfering with the internal display light. Can be specular – mirror
images (reflections) of other light sources or objects in the room; or diffuse, randomly scattered light onto the display surface

48
Q

Display Resolution

A

Measure of the ability of the digital display to produce separate images of two points with high fidelity. Test performed using a test pattern.

49
Q

Display Noise

A

High frequency patterns or fluctuations that interfere with the true signal. Test is performed using a test pattern.

50
Q

Response rate

A

The amount of time it takes for the crystal to go from an on to an off state and vice versa.

51
Q

Aspect ratio

A

the ratio of the width to the height of the monitor – most LDC’s are 16:9 (widescreen)

52
Q

Aperture Ratio

A

the portion of the pixel face that is available to transmit light.

53
Q

Viewable area

A

measurement diagonally from one corner to the opposite of the viewing screen (does not include the casing).

SPRING 2024: Principles II (13 decks)

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